/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Kenneth Almquist.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/param.h>
#include <pwd.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <time.h>

#include "shell.h"
#include "parser.h"
#include "nodes.h"
#include "expand.h"     /* defines rmescapes() */
#include "syntax.h"
#include "options.h"
#include "input.h"
#include "output.h"
#include "var.h"
#include "error.h"
#include "memalloc.h"
#include "mystring.h"
#include "alias.h"
#include "show.h"
#include "eval.h"
#include "exec.h"       /* to check for special builtins */
#include "main.h"
#include "jobs.h"
#ifndef NO_HISTORY
#include "myhistedit.h"
#endif

/*
 * Shell command parser.
 */

#define PROMPTLEN       192

/* values of checkkwd variable */
#define CHKALIAS        0x1
#define CHKKWD          0x2
#define CHKNL           0x4

/* values returned by readtoken */
#include "token.h"



struct heredoc {
        struct heredoc *next;   /* next here document in list */
        union node *here;               /* redirection node */
        char *eofmark;          /* string indicating end of input */
        int striptabs;          /* if set, strip leading tabs */
};

struct parser_temp {
        struct parser_temp *next;
        void *data;
};


static struct heredoc *heredoclist;     /* list of here documents to read */
static int doprompt;            /* if set, prompt the user */
static int needprompt;          /* true if interactive and at start of line */
static int lasttoken;           /* last token read */
static int tokpushback;         /* last token pushed back */
static char *wordtext;          /* text of last word returned by readtoken */
static int checkkwd;
static struct nodelist *backquotelist;
static union node *redirnode;
static struct heredoc *heredoc;
static int quoteflag;           /* set if (part of) last token was quoted */
static int startlinno;          /* line # where last token started */
static int funclinno;           /* line # where the current function started */
static struct parser_temp *parser_temp;

#define NOEOFMARK ((const char *)&heredoclist)


static union node *list(int);
static union node *andor(void);
static union node *pipeline(void);
static union node *command(void);
static union node *simplecmd(union node **, union node *);
static union node *makename(void);
static union node *makebinary(int type, union node *n1, union node *n2);
static void parsefname(void);
static void parseheredoc(void);
static int peektoken(void);
static int readtoken(void);
static int xxreadtoken(void);
static int readtoken1(int, const char *, const char *, int);
static int noexpand(char *);
static void consumetoken(int);
static void synexpect(int) __dead2;
static void synerror(const char *) __dead2;
static void setprompt(int);
static int pgetc_linecont(void);
static void getusername(char *, size_t);


static void *
parser_temp_alloc(size_t len)
{
        struct parser_temp *t;

        INTOFF;
        t = ckmalloc(sizeof(*t));
        t->data = NULL;
        t->next = parser_temp;
        parser_temp = t;
        t->data = ckmalloc(len);
        INTON;
        return t->data;
}


static void *
parser_temp_realloc(void *ptr, size_t len)
{
        struct parser_temp *t;

        INTOFF;
        t = parser_temp;
        if (ptr != t->data)
                error("bug: parser_temp_realloc misused");
        t->data = ckrealloc(t->data, len);
        INTON;
        return t->data;
}


static void
parser_temp_free_upto(void *ptr)
{
        struct parser_temp *t;
        int done = 0;

        INTOFF;
        while (parser_temp != NULL && !done) {
                t = parser_temp;
                parser_temp = t->next;
                done = t->data == ptr;
                ckfree(t->data);
                ckfree(t);
        }
        INTON;
        if (!done)
                error("bug: parser_temp_free_upto misused");
}


static void
parser_temp_free_all(void)
{
        struct parser_temp *t;

        INTOFF;
        while (parser_temp != NULL) {
                t = parser_temp;
                parser_temp = t->next;
                ckfree(t->data);
                ckfree(t);
        }
        INTON;
}


/*
 * Read and parse a command.  Returns NEOF on end of file.  (NULL is a
 * valid parse tree indicating a blank line.)
 */

union node *
parsecmd(int interact)
{
        int t;

        /* This assumes the parser is not re-entered,
         * which could happen if we add command substitution on PS1/PS2.
         */
        parser_temp_free_all();
        heredoclist = NULL;

        tokpushback = 0;
        checkkwd = 0;
        doprompt = interact;
        if (doprompt)
                setprompt(1);
        else
                setprompt(0);
        needprompt = 0;
        t = readtoken();
        if (t == TEOF)
                return NEOF;
        if (t == TNL)
                return NULL;
        tokpushback++;
        return list(1);
}


/*
 * Read and parse words for wordexp.
 * Returns a list of NARG nodes; NULL if there are no words.
 */
union node *
parsewordexp(void)
{
        union node *n, *first = NULL, **pnext;
        int t;

        /* This assumes the parser is not re-entered,
         * which could happen if we add command substitution on PS1/PS2.
         */
        parser_temp_free_all();
        heredoclist = NULL;

        tokpushback = 0;
        checkkwd = 0;
        doprompt = 0;
        setprompt(0);
        needprompt = 0;
        pnext = &first;
        while ((t = readtoken()) != TEOF) {
                if (t != TWORD)
                        synexpect(TWORD);
                n = makename();
                *pnext = n;
                pnext = &n->narg.next;
        }
        return first;
}


static union node *
list(int nlflag)
{
        union node *ntop, *n1, *n2, *n3;
        int tok;

        checkkwd = CHKNL | CHKKWD | CHKALIAS;
        if (!nlflag && tokendlist[peektoken()])
                return NULL;
        ntop = n1 = NULL;
        for (;;) {
                n2 = andor();
                tok = readtoken();
                if (tok == TBACKGND) {
                        if (n2 != NULL && n2->type == NPIPE) {
                                n2->npipe.backgnd = 1;
                        } else if (n2 != NULL && n2->type == NREDIR) {
                                n2->type = NBACKGND;
                        } else {
                                n3 = (union node *)stalloc(sizeof (struct nredir));
                                n3->type = NBACKGND;
                                n3->nredir.n = n2;
                                n3->nredir.redirect = NULL;
                                n2 = n3;
                        }
                }
                if (ntop == NULL)
                        ntop = n2;
                else if (n1 == NULL) {
                        n1 = makebinary(NSEMI, ntop, n2);
                        ntop = n1;
                }
                else {
                        n3 = makebinary(NSEMI, n1->nbinary.ch2, n2);
                        n1->nbinary.ch2 = n3;
                        n1 = n3;
                }
                switch (tok) {
                case TBACKGND:
                case TSEMI:
                        tok = readtoken();
                        /* FALLTHROUGH */
                case TNL:
                        if (tok == TNL) {
                                parseheredoc();
                                if (nlflag)
                                        return ntop;
                        } else if (tok == TEOF && nlflag) {
                                parseheredoc();
                                return ntop;
                        } else {
                                tokpushback++;
                        }
                        checkkwd = CHKNL | CHKKWD | CHKALIAS;
                        if (!nlflag && tokendlist[peektoken()])
                                return ntop;
                        break;
                case TEOF:
                        if (heredoclist)
                                parseheredoc();
                        else
                                pungetc();              /* push back EOF on input */
                        return ntop;
                default:
                        if (nlflag)
                                synexpect(-1);
                        tokpushback++;
                        return ntop;
                }
        }
}



static union node *
andor(void)
{
        union node *n;
        int t;

        n = pipeline();
        for (;;) {
                if ((t = readtoken()) == TAND) {
                        t = NAND;
                } else if (t == TOR) {
                        t = NOR;
                } else {
                        tokpushback++;
                        return n;
                }
                n = makebinary(t, n, pipeline());
        }
}



static union node *
pipeline(void)
{
        union node *n1, *n2, *pipenode;
        struct nodelist *lp, *prev;
        int negate, t;

        negate = 0;
        checkkwd = CHKNL | CHKKWD | CHKALIAS;
        TRACE(("pipeline: entered\n"));
        while (readtoken() == TNOT)
                negate = !negate;
        tokpushback++;
        n1 = command();
        if (readtoken() == TPIPE) {
                pipenode = (union node *)stalloc(sizeof (struct npipe));
                pipenode->type = NPIPE;
                pipenode->npipe.backgnd = 0;
                lp = (struct nodelist *)stalloc(sizeof (struct nodelist));
                pipenode->npipe.cmdlist = lp;
                lp->n = n1;
                do {
                        prev = lp;
                        lp = (struct nodelist *)stalloc(sizeof (struct nodelist));
                        checkkwd = CHKNL | CHKKWD | CHKALIAS;
                        t = readtoken();
                        tokpushback++;
                        if (t == TNOT)
                                lp->n = pipeline();
                        else
                                lp->n = command();
                        prev->next = lp;
                } while (readtoken() == TPIPE);
                lp->next = NULL;
                n1 = pipenode;
        }
        tokpushback++;
        if (negate) {
                n2 = (union node *)stalloc(sizeof (struct nnot));
                n2->type = NNOT;
                n2->nnot.com = n1;
                return n2;
        } else
                return n1;
}



static union node *
command(void)
{
        union node *n1, *n2;
        union node *ap, **app;
        union node *cp, **cpp;
        union node *redir, **rpp;
        int t;
        int is_subshell;

        checkkwd = CHKNL | CHKKWD | CHKALIAS;
        is_subshell = 0;
        redir = NULL;
        n1 = NULL;
        rpp = &redir;

        /* Check for redirection which may precede command */
        while (readtoken() == TREDIR) {
                *rpp = n2 = redirnode;
                rpp = &n2->nfile.next;
                parsefname();
        }
        tokpushback++;

        switch (readtoken()) {
        case TIF:
                n1 = (union node *)stalloc(sizeof (struct nif));
                n1->type = NIF;
                if ((n1->nif.test = list(0)) == NULL)
                        synexpect(-1);
                consumetoken(TTHEN);
                n1->nif.ifpart = list(0);
                n2 = n1;
                while (readtoken() == TELIF) {
                        n2->nif.elsepart = (union node *)stalloc(sizeof (struct nif));
                        n2 = n2->nif.elsepart;
                        n2->type = NIF;
                        if ((n2->nif.test = list(0)) == NULL)
                                synexpect(-1);
                        consumetoken(TTHEN);
                        n2->nif.ifpart = list(0);
                }
                if (lasttoken == TELSE)
                        n2->nif.elsepart = list(0);
                else {
                        n2->nif.elsepart = NULL;
                        tokpushback++;
                }
                consumetoken(TFI);
                checkkwd = CHKKWD | CHKALIAS;
                break;
        case TWHILE:
        case TUNTIL:
                t = lasttoken;
                if ((n1 = list(0)) == NULL)
                        synexpect(-1);
                consumetoken(TDO);
                n1 = makebinary((t == TWHILE)? NWHILE : NUNTIL, n1, list(0));
                consumetoken(TDONE);
                checkkwd = CHKKWD | CHKALIAS;
                break;
        case TFOR:
                if (readtoken() != TWORD || quoteflag || ! goodname(wordtext))
                        synerror("Bad for loop variable");
                n1 = (union node *)stalloc(sizeof (struct nfor));
                n1->type = NFOR;
                n1->nfor.var = wordtext;
                checkkwd = CHKNL;
                if (readtoken() == TWORD && !quoteflag &&
                    equal(wordtext, "in")) {
                        app = &ap;
                        while (readtoken() == TWORD) {
                                n2 = makename();
                                *app = n2;
                                app = &n2->narg.next;
                        }
                        *app = NULL;
                        n1->nfor.args = ap;
                        if (lasttoken == TNL)
                                tokpushback++;
                        else if (lasttoken != TSEMI)
                                synexpect(-1);
                } else {
                        static char argvars[5] = {
                                CTLVAR, VSNORMAL|VSQUOTE, '@', '=', '\0'
                        };
                        n2 = (union node *)stalloc(sizeof (struct narg));
                        n2->type = NARG;
                        n2->narg.text = argvars;
                        n2->narg.backquote = NULL;
                        n2->narg.next = NULL;
                        n1->nfor.args = n2;
                        /*
                         * Newline or semicolon here is optional (but note
                         * that the original Bourne shell only allowed NL).
                         */
                        if (lasttoken != TSEMI)
                                tokpushback++;
                }
                checkkwd = CHKNL | CHKKWD | CHKALIAS;
                if ((t = readtoken()) == TDO)
                        t = TDONE;
                else if (t == TBEGIN)
                        t = TEND;
                else
                        synexpect(-1);
                n1->nfor.body = list(0);
                consumetoken(t);
                checkkwd = CHKKWD | CHKALIAS;
                break;
        case TCASE:
                n1 = (union node *)stalloc(sizeof (struct ncase));
                n1->type = NCASE;
                consumetoken(TWORD);
                n1->ncase.expr = makename();
                checkkwd = CHKNL;
                if (readtoken() != TWORD || ! equal(wordtext, "in"))
                        synerror("expecting \"in\"");
                cpp = &n1->ncase.cases;
                checkkwd = CHKNL | CHKKWD, readtoken();
                while (lasttoken != TESAC) {
                        *cpp = cp = (union node *)stalloc(sizeof (struct nclist));
                        cp->type = NCLIST;
                        app = &cp->nclist.pattern;
                        if (lasttoken == TLP)
                                readtoken();
                        for (;;) {
                                *app = ap = makename();
                                checkkwd = CHKNL | CHKKWD;
                                if (readtoken() != TPIPE)
                                        break;
                                app = &ap->narg.next;
                                readtoken();
                        }
                        ap->narg.next = NULL;
                        if (lasttoken != TRP)
                                synexpect(TRP);
                        cp->nclist.body = list(0);

                        checkkwd = CHKNL | CHKKWD | CHKALIAS;
                        if ((t = readtoken()) != TESAC) {
                                if (t == TENDCASE)
                                        ;
                                else if (t == TFALLTHRU)
                                        cp->type = NCLISTFALLTHRU;
                                else
                                        synexpect(TENDCASE);
                                checkkwd = CHKNL | CHKKWD, readtoken();
                        }
                        cpp = &cp->nclist.next;
                }
                *cpp = NULL;
                checkkwd = CHKKWD | CHKALIAS;
                break;
        case TLP:
                n1 = (union node *)stalloc(sizeof (struct nredir));
                n1->type = NSUBSHELL;
                n1->nredir.n = list(0);
                n1->nredir.redirect = NULL;
                consumetoken(TRP);
                checkkwd = CHKKWD | CHKALIAS;
                is_subshell = 1;
                break;
        case TBEGIN:
                n1 = list(0);
                consumetoken(TEND);
                checkkwd = CHKKWD | CHKALIAS;
                break;
        /* A simple command must have at least one redirection or word. */
        case TBACKGND:
        case TSEMI:
        case TAND:
        case TOR:
        case TPIPE:
        case TENDCASE:
        case TFALLTHRU:
        case TEOF:
        case TNL:
        case TRP:
                if (!redir)
                        synexpect(-1);
        case TWORD:
                tokpushback++;
                n1 = simplecmd(rpp, redir);
                return n1;
        default:
                synexpect(-1);
        }

        /* Now check for redirection which may follow command */
        while (readtoken() == TREDIR) {
                *rpp = n2 = redirnode;
                rpp = &n2->nfile.next;
                parsefname();
        }
        tokpushback++;
        *rpp = NULL;
        if (redir) {
                if (!is_subshell) {
                        n2 = (union node *)stalloc(sizeof (struct nredir));
                        n2->type = NREDIR;
                        n2->nredir.n = n1;
                        n1 = n2;
                }
                n1->nredir.redirect = redir;
        }

        return n1;
}


static union node *
simplecmd(union node **rpp, union node *redir)
{
        union node *args, **app;
        union node **orig_rpp = rpp;
        union node *n = NULL;
        int special;
        int savecheckkwd;

        /* If we don't have any redirections already, then we must reset */
        /* rpp to be the address of the local redir variable.  */
        if (redir == NULL)
                rpp = &redir;

        args = NULL;
        app = &args;
        /*
         * We save the incoming value, because we need this for shell
         * functions.  There can not be a redirect or an argument between
         * the function name and the open parenthesis.
         */
        orig_rpp = rpp;

        savecheckkwd = CHKALIAS;

        for (;;) {
                checkkwd = savecheckkwd;
                if (readtoken() == TWORD) {
                        n = makename();
                        *app = n;
                        app = &n->narg.next;
                        if (savecheckkwd != 0 && !isassignment(wordtext))
                                savecheckkwd = 0;
                } else if (lasttoken == TREDIR) {
                        *rpp = n = redirnode;
                        rpp = &n->nfile.next;
                        parsefname();   /* read name of redirection file */
                } else if (lasttoken == TLP && app == &args->narg.next
                                            && rpp == orig_rpp) {
                        /* We have a function */
                        consumetoken(TRP);
                        funclinno = plinno;
                        /*
                         * - Require plain text.
                         * - Functions with '/' cannot be called.
                         * - Reject name=().
                         * - Reject ksh extended glob patterns.
                         */
                        if (!noexpand(n->narg.text) || quoteflag ||
                            strchr(n->narg.text, '/') ||
                            strchr("!%*+-=?@}~",
                                n->narg.text[strlen(n->narg.text) - 1]))
                                synerror("Bad function name");
                        rmescapes(n->narg.text);
                        if (find_builtin(n->narg.text, &special) >= 0 &&
                            special)
                                synerror("Cannot override a special builtin with a function");
                        n->type = NDEFUN;
                        n->narg.next = command();
                        funclinno = 0;
                        return n;
                } else {
                        tokpushback++;
                        break;
                }
        }
        *app = NULL;
        *rpp = NULL;
        n = (union node *)stalloc(sizeof (struct ncmd));
        n->type = NCMD;
        n->ncmd.args = args;
        n->ncmd.redirect = redir;
        return n;
}

static union node *
makename(void)
{
        union node *n;

        n = (union node *)stalloc(sizeof (struct narg));
        n->type = NARG;
        n->narg.next = NULL;
        n->narg.text = wordtext;
        n->narg.backquote = backquotelist;
        return n;
}

static union node *
makebinary(int type, union node *n1, union node *n2)
{
        union node *n;

        n = (union node *)stalloc(sizeof (struct nbinary));
        n->type = type;
        n->nbinary.ch1 = n1;
        n->nbinary.ch2 = n2;
        return (n);
}

void
forcealias(void)
{
        checkkwd |= CHKALIAS;
}

void
fixredir(union node *n, const char *text, int err)
{
        TRACE(("Fix redir %s %d\n", text, err));
        if (!err)
                n->ndup.vname = NULL;

        if (is_digit(text[0]) && text[1] == '\0')
                n->ndup.dupfd = digit_val(text[0]);
        else if (text[0] == '-' && text[1] == '\0')
                n->ndup.dupfd = -1;
        else {

                if (err)
                        synerror("Bad fd number");
                else
                        n->ndup.vname = makename();
        }
}


static void
parsefname(void)
{
        union node *n = redirnode;

        consumetoken(TWORD);
        if (n->type == NHERE) {
                struct heredoc *here = heredoc;
                struct heredoc *p;

                if (quoteflag == 0)
                        n->type = NXHERE;
                TRACE(("Here document %d\n", n->type));
                if (here->striptabs) {
                        while (*wordtext == '\t')
                                wordtext++;
                }
                if (! noexpand(wordtext))
                        synerror("Illegal eof marker for << redirection");
                rmescapes(wordtext);
                here->eofmark = wordtext;
                here->next = NULL;
                if (heredoclist == NULL)
                        heredoclist = here;
                else {
                        for (p = heredoclist ; p->next ; p = p->next);
                        p->next = here;
                }
        } else if (n->type == NTOFD || n->type == NFROMFD) {
                fixredir(n, wordtext, 0);
        } else {
                n->nfile.fname = makename();
        }
}


/*
 * Input any here documents.
 */

static void
parseheredoc(void)
{
        struct heredoc *here;
        union node *n;

        while (heredoclist) {
                here = heredoclist;
                heredoclist = here->next;
                if (needprompt) {
                        setprompt(2);
                        needprompt = 0;
                }
                readtoken1(pgetc(), here->here->type == NHERE? SQSYNTAX : DQSYNTAX,
                                here->eofmark, here->striptabs);
                n = makename();
                here->here->nhere.doc = n;
        }
}

static int
peektoken(void)
{
        int t;

        t = readtoken();
        tokpushback++;
        return (t);
}

static int
readtoken(void)
{
        int t;
        struct alias *ap;
#ifdef DEBUG
        int alreadyseen = tokpushback;
#endif

        top:
        t = xxreadtoken();

        /*
         * eat newlines
         */
        if (checkkwd & CHKNL) {
                while (t == TNL) {
                        parseheredoc();
                        t = xxreadtoken();
                }
        }

        /*
         * check for keywords and aliases
         */
        if (t == TWORD && !quoteflag)
        {
                const char * const *pp;

                if (checkkwd & CHKKWD)
                        for (pp = parsekwd; *pp; pp++) {
                                if (**pp == *wordtext && equal(*pp, wordtext))
                                {
                                        lasttoken = t = pp - parsekwd + KWDOFFSET;
                                        TRACE(("keyword %s recognized\n", tokname[t]));
                                        goto out;
                                }
                        }
                if (checkkwd & CHKALIAS &&
                    (ap = lookupalias(wordtext, 1)) != NULL) {
                        pushstring(ap->val, strlen(ap->val), ap);
                        goto top;
                }
        }
out:
        if (t != TNOT)
                checkkwd = 0;

#ifdef DEBUG
        if (!alreadyseen)
            TRACE(("token %s %s\n", tokname[t], t == TWORD ? wordtext : ""));
        else
            TRACE(("reread token %s %s\n", tokname[t], t == TWORD ? wordtext : ""));
#endif
        return (t);
}


/*
 * Read the next input token.
 * If the token is a word, we set backquotelist to the list of cmds in
 *      backquotes.  We set quoteflag to true if any part of the word was
 *      quoted.
 * If the token is TREDIR, then we set redirnode to a structure containing
 *      the redirection.
 * In all cases, the variable startlinno is set to the number of the line
 *      on which the token starts.
 *
 * [Change comment:  here documents and internal procedures]
 * [Readtoken shouldn't have any arguments.  Perhaps we should make the
 *  word parsing code into a separate routine.  In this case, readtoken
 *  doesn't need to have any internal procedures, but parseword does.
 *  We could also make parseoperator in essence the main routine, and
 *  have parseword (readtoken1?) handle both words and redirection.]
 */

#define RETURN(token)   return lasttoken = token

static int
xxreadtoken(void)
{
        int c;

        if (tokpushback) {
                tokpushback = 0;
                return lasttoken;
        }
        if (needprompt) {
                setprompt(2);
                needprompt = 0;
        }
        startlinno = plinno;
        for (;;) {      /* until token or start of word found */
                c = pgetc_macro();
                switch (c) {
                case ' ': case '\t':
                        continue;
                case '#':
                        while ((c = pgetc()) != '\n' && c != PEOF);
                        pungetc();
                        continue;
                case '\\':
                        if (pgetc() == '\n') {
                                startlinno = ++plinno;
                                if (doprompt)
                                        setprompt(2);
                                else
                                        setprompt(0);
                                continue;
                        }
                        pungetc();
                        /* FALLTHROUGH */
                default:
                        return readtoken1(c, BASESYNTAX, (char *)NULL, 0);
                case '\n':
                        plinno++;
                        needprompt = doprompt;
                        RETURN(TNL);
                case PEOF:
                        RETURN(TEOF);
                case '&':
                        if (pgetc_linecont() == '&')
                                RETURN(TAND);
                        pungetc();
                        RETURN(TBACKGND);
                case '|':
                        if (pgetc_linecont() == '|')
                                RETURN(TOR);
                        pungetc();
                        RETURN(TPIPE);
                case ';':
                        c = pgetc_linecont();
                        if (c == ';')
                                RETURN(TENDCASE);
                        else if (c == '&')
                                RETURN(TFALLTHRU);
                        pungetc();
                        RETURN(TSEMI);
                case '(':
                        RETURN(TLP);
                case ')':
                        RETURN(TRP);
                }
        }
#undef RETURN
}


#define MAXNEST_static 8
struct tokenstate
{
        const char *syntax; /* *SYNTAX */
        int parenlevel; /* levels of parentheses in arithmetic */
        enum tokenstate_category
        {
                TSTATE_TOP,
                TSTATE_VAR_OLD, /* ${var+-=?}, inherits dquotes */
                TSTATE_VAR_NEW, /* other ${var...}, own dquote state */
                TSTATE_ARITH
        } category;
};


/*
 * Check to see whether we are at the end of the here document.  When this
 * is called, c is set to the first character of the next input line.  If
 * we are at the end of the here document, this routine sets the c to PEOF.
 * The new value of c is returned.
 */

static int
checkend(int c, const char *eofmark, int striptabs)
{
        if (striptabs) {
                while (c == '\t')
                        c = pgetc();
        }
        if (c == *eofmark) {
                int c2;
                const char *q;

                for (q = eofmark + 1; c2 = pgetc(), *q != '\0' && c2 == *q; q++)
                        ;
                if ((c2 == PEOF || c2 == '\n') && *q == '\0') {
                        c = PEOF;
                        if (c2 == '\n') {
                                plinno++;
                                needprompt = doprompt;
                        }
                } else {
                        pungetc();
                        pushstring(eofmark + 1, q - (eofmark + 1), NULL);
                }
        } else if (c == '\n' && *eofmark == '\0') {
                c = PEOF;
                plinno++;
                needprompt = doprompt;
        }
        return (c);
}


/*
 * Parse a redirection operator.  The variable "out" points to a string
 * specifying the fd to be redirected.  The variable "c" contains the
 * first character of the redirection operator.
 */

static void
parseredir(char *out, int c)
{
        char fd = *out;
        union node *np;

        np = (union node *)stalloc(sizeof (struct nfile));
        if (c == '>') {
                np->nfile.fd = 1;
                c = pgetc_linecont();
                if (c == '>')
                        np->type = NAPPEND;
                else if (c == '&')
                        np->type = NTOFD;
                else if (c == '|')
                        np->type = NCLOBBER;
                else {
                        np->type = NTO;
                        pungetc();
                }
        } else {        /* c == '<' */
                np->nfile.fd = 0;
                c = pgetc_linecont();
                if (c == '<') {
                        if (sizeof (struct nfile) != sizeof (struct nhere)) {
                                np = (union node *)stalloc(sizeof (struct nhere));
                                np->nfile.fd = 0;
                        }
                        np->type = NHERE;
                        heredoc = (struct heredoc *)stalloc(sizeof (struct heredoc));
                        heredoc->here = np;
                        if ((c = pgetc_linecont()) == '-') {
                                heredoc->striptabs = 1;
                        } else {
                                heredoc->striptabs = 0;
                                pungetc();
                        }
                } else if (c == '&')
                        np->type = NFROMFD;
                else if (c == '>')
                        np->type = NFROMTO;
                else {
                        np->type = NFROM;
                        pungetc();
                }
        }
        if (fd != '\0')
                np->nfile.fd = digit_val(fd);
        redirnode = np;
}

/*
 * Called to parse command substitutions.
 */

static char *
parsebackq(char *out, struct nodelist **pbqlist,
                int oldstyle, int dblquote, int quoted)
{
        struct nodelist **nlpp;
        union node *n;
        char *volatile str;
        struct jmploc jmploc;
        struct jmploc *const savehandler = handler;
        size_t savelen;
        int saveprompt;
        const int bq_startlinno = plinno;
        char *volatile ostr = NULL;
        struct parsefile *const savetopfile = getcurrentfile();
        struct heredoc *const saveheredoclist = heredoclist;
        struct heredoc *here;

        str = NULL;
        if (setjmp(jmploc.loc)) {
                popfilesupto(savetopfile);
                if (str)
                        ckfree(str);
                if (ostr)
                        ckfree(ostr);
                heredoclist = saveheredoclist;
                handler = savehandler;
                if (exception == EXERROR) {
                        startlinno = bq_startlinno;
                        synerror("Error in command substitution");
                }
                longjmp(handler->loc, 1);
        }
        INTOFF;
        savelen = out - stackblock();
        if (savelen > 0) {
                str = ckmalloc(savelen);
                memcpy(str, stackblock(), savelen);
        }
        handler = &jmploc;
        heredoclist = NULL;
        INTON;
        if (oldstyle) {
                /* We must read until the closing backquote, giving special
                   treatment to some slashes, and then push the string and
                   reread it as input, interpreting it normally.  */
                char *oout;
                int c;
                int olen;


                STARTSTACKSTR(oout);
                for (;;) {
                        if (needprompt) {
                                setprompt(2);
                                needprompt = 0;
                        }
                        CHECKSTRSPACE(2, oout);
                        c = pgetc_linecont();
                        if (c == '`')
                                break;
                        switch (c) {
                        case '\\':
                                c = pgetc();
                                if (c != '\\' && c != '`' && c != '$'
                                    && (!dblquote || c != '"'))
                                        USTPUTC('\\', oout);
                                break;

                        case '\n':
                                plinno++;
                                needprompt = doprompt;
                                break;

                        case PEOF:
                                startlinno = plinno;
                                synerror("EOF in backquote substitution");
                                break;

                        default:
                                break;
                        }
                        USTPUTC(c, oout);
                }
                USTPUTC('\0', oout);
                olen = oout - stackblock();
                INTOFF;
                ostr = ckmalloc(olen);
                memcpy(ostr, stackblock(), olen);
                setinputstring(ostr, 1);
                INTON;
        }
        nlpp = pbqlist;
        while (*nlpp)
                nlpp = &(*nlpp)->next;
        *nlpp = (struct nodelist *)stalloc(sizeof (struct nodelist));
        (*nlpp)->next = NULL;

        if (oldstyle) {
                saveprompt = doprompt;
                doprompt = 0;
        }

        n = list(0);

        if (oldstyle) {
                if (peektoken() != TEOF)
                        synexpect(-1);
                doprompt = saveprompt;
        } else
                consumetoken(TRP);

        (*nlpp)->n = n;
        if (oldstyle) {
                /*
                 * Start reading from old file again, ignoring any pushed back
                 * tokens left from the backquote parsing
                 */
                popfile();
                tokpushback = 0;
        }
        STARTSTACKSTR(out);
        CHECKSTRSPACE(savelen + 1, out);
        INTOFF;
        if (str) {
                memcpy(out, str, savelen);
                STADJUST(savelen, out);
                ckfree(str);
                str = NULL;
        }
        if (ostr) {
                ckfree(ostr);
                ostr = NULL;
        }
        here = saveheredoclist;
        if (here != NULL) {
                while (here->next != NULL)
                        here = here->next;
                here->next = heredoclist;
                heredoclist = saveheredoclist;
        }
        handler = savehandler;
        INTON;
        if (quoted)
                USTPUTC(CTLBACKQ | CTLQUOTE, out);
        else
                USTPUTC(CTLBACKQ, out);
        return out;
}


/*
 * Called to parse a backslash escape sequence inside $'...'.
 * The backslash has already been read.
 */
static char *
readcstyleesc(char *out)
{
        int c, vc, i, n;
        unsigned int v;

        c = pgetc();
        switch (c) {
        case '\0':
                synerror("Unterminated quoted string");
        case '\n':
                plinno++;
                if (doprompt)
                        setprompt(2);
                else
                        setprompt(0);
                return out;
        case '\\':
        case '\'':
        case '"':
                v = c;
                break;
        case 'a': v = '\a'; break;
        case 'b': v = '\b'; break;
        case 'e': v = '\033'; break;
        case 'f': v = '\f'; break;
        case 'n': v = '\n'; break;
        case 'r': v = '\r'; break;
        case 't': v = '\t'; break;
        case 'v': v = '\v'; break;
        case 'x':
                  v = 0;
                  for (;;) {
                          c = pgetc();
                          if (c >= '0' && c <= '9')
                                  v = (v << 4) + c - '0';
                          else if (c >= 'A' && c <= 'F')
                                  v = (v << 4) + c - 'A' + 10;
                          else if (c >= 'a' && c <= 'f')
                                  v = (v << 4) + c - 'a' + 10;
                          else
                                  break;
                  }
                  pungetc();
                  break;
        case '0': case '1': case '2': case '3':
        case '4': case '5': case '6': case '7':
                  v = c - '0';
                  c = pgetc();
                  if (c >= '0' && c <= '7') {
                          v <<= 3;
                          v += c - '0';
                          c = pgetc();
                          if (c >= '0' && c <= '7') {
                                  v <<= 3;
                                  v += c - '0';
                          } else
                                  pungetc();
                  } else
                          pungetc();
                  break;
        case 'c':
                  c = pgetc();
                  if (c < 0x3f || c > 0x7a || c == 0x60)
                          synerror("Bad escape sequence");
                  if (c == '\\' && pgetc() != '\\')
                          synerror("Bad escape sequence");
                  if (c == '?')
                          v = 127;
                  else
                          v = c & 0x1f;
                  break;
        case 'u':
        case 'U':
                  n = c == 'U' ? 8 : 4;
                  v = 0;
                  for (i = 0; i < n; i++) {
                          c = pgetc();
                          if (c >= '0' && c <= '9')
                                  v = (v << 4) + c - '0';
                          else if (c >= 'A' && c <= 'F')
                                  v = (v << 4) + c - 'A' + 10;
                          else if (c >= 'a' && c <= 'f')
                                  v = (v << 4) + c - 'a' + 10;
                          else
                                  synerror("Bad escape sequence");
                  }
                  if (v == 0 || (v >= 0xd800 && v <= 0xdfff))
                          synerror("Bad escape sequence");
                  /* We really need iconv here. */
                  if (initial_localeisutf8 && v > 127) {
                          CHECKSTRSPACE(4, out);
                          /*
                           * We cannot use wctomb() as the locale may have
                           * changed.
                           */
                          if (v <= 0x7ff) {
                                  USTPUTC(0xc0 | v >> 6, out);
                                  USTPUTC(0x80 | (v & 0x3f), out);
                                  return out;
                          } else if (v <= 0xffff) {
                                  USTPUTC(0xe0 | v >> 12, out);
                                  USTPUTC(0x80 | ((v >> 6) & 0x3f), out);
                                  USTPUTC(0x80 | (v & 0x3f), out);
                                  return out;
                          } else if (v <= 0x10ffff) {
                                  USTPUTC(0xf0 | v >> 18, out);
                                  USTPUTC(0x80 | ((v >> 12) & 0x3f), out);
                                  USTPUTC(0x80 | ((v >> 6) & 0x3f), out);
                                  USTPUTC(0x80 | (v & 0x3f), out);
                                  return out;
                          }
                  }
                  if (v > 127)
                          v = '?';
                  break;
        default:
                  synerror("Bad escape sequence");
        }
        vc = (char)v;
        /*
         * We can't handle NUL bytes.
         * POSIX says we should skip till the closing quote.
         */
        if (vc == '\0') {
                while ((c = pgetc()) != '\'') {
                        if (c == '\\')
                                c = pgetc();
                        if (c == PEOF)
                                synerror("Unterminated quoted string");
                        if (c == '\n') {
                                plinno++;
                                if (doprompt)
                                        setprompt(2);
                                else
                                        setprompt(0);
                        }
                }
                pungetc();
                return out;
        }
        if (SQSYNTAX[vc] == CCTL)
                USTPUTC(CTLESC, out);
        USTPUTC(vc, out);
        return out;
}


/*
 * If eofmark is NULL, read a word or a redirection symbol.  If eofmark
 * is not NULL, read a here document.  In the latter case, eofmark is the
 * word which marks the end of the document and striptabs is true if
 * leading tabs should be stripped from the document.  The argument firstc
 * is the first character of the input token or document.
 *
 * Because C does not have internal subroutines, I have simulated them
 * using goto's to implement the subroutine linkage.  The following macros
 * will run code that appears at the end of readtoken1.
 */

#define PARSESUB()      {goto parsesub; parsesub_return:;}
#define PARSEARITH()    {goto parsearith; parsearith_return:;}

static int
readtoken1(int firstc, char const *initialsyntax, const char *eofmark,
    int striptabs)
{
        int c = firstc;
        char *out;
        int len;
        struct nodelist *bqlist;
        int quotef;
        int newvarnest;
        int level;
        int synentry;
        struct tokenstate state_static[MAXNEST_static];
        int maxnest = MAXNEST_static;
        struct tokenstate *state = state_static;
        int sqiscstyle = 0;

        startlinno = plinno;
        quotef = 0;
        bqlist = NULL;
        newvarnest = 0;
        level = 0;
        state[level].syntax = initialsyntax;
        state[level].parenlevel = 0;
        state[level].category = TSTATE_TOP;

        STARTSTACKSTR(out);
        loop: { /* for each line, until end of word */
                if (eofmark && eofmark != NOEOFMARK)
                        /* set c to PEOF if at end of here document */
                        c = checkend(c, eofmark, striptabs);
                for (;;) {      /* until end of line or end of word */
                        CHECKSTRSPACE(4, out);  /* permit 4 calls to USTPUTC */

                        synentry = state[level].syntax[c];

                        switch(synentry) {
                        case CNL:       /* '\n' */
                                if (level == 0)
                                        goto endword;   /* exit outer loop */
                                /* FALLTHROUGH */
                        case CQNL:
                                USTPUTC(c, out);
                                plinno++;
                                if (doprompt)
                                        setprompt(2);
                                else
                                        setprompt(0);
                                c = pgetc();
                                goto loop;              /* continue outer loop */
                        case CSBACK:
                                if (sqiscstyle) {
                                        out = readcstyleesc(out);
                                        break;
                                }
                                /* FALLTHROUGH */
                        case CWORD:
                                USTPUTC(c, out);
                                break;
                        case CCTL:
                                if (eofmark == NULL || initialsyntax != SQSYNTAX)
                                        USTPUTC(CTLESC, out);
                                USTPUTC(c, out);
                                break;
                        case CBACK:     /* backslash */
                                c = pgetc();
                                if (c == PEOF) {
                                        USTPUTC('\\', out);
                                        pungetc();
                                } else if (c == '\n') {
                                        plinno++;
                                        if (doprompt)
                                                setprompt(2);
                                        else
                                                setprompt(0);
                                } else {
                                        if (state[level].syntax == DQSYNTAX &&
                                            c != '\\' && c != '`' && c != '$' &&
                                            (c != '"' || (eofmark != NULL &&
                                                newvarnest == 0)) &&
                                            (c != '}' || state[level].category != TSTATE_VAR_OLD))
                                                USTPUTC('\\', out);
                                        if ((eofmark == NULL ||
                                            newvarnest > 0) &&
                                            state[level].syntax == BASESYNTAX)
                                                USTPUTC(CTLQUOTEMARK, out);
                                        if (SQSYNTAX[c] == CCTL)
                                                USTPUTC(CTLESC, out);
                                        USTPUTC(c, out);
                                        if ((eofmark == NULL ||
                                            newvarnest > 0) &&
                                            state[level].syntax == BASESYNTAX &&
                                            state[level].category == TSTATE_VAR_OLD)
                                                USTPUTC(CTLQUOTEEND, out);
                                        quotef++;
                                }
                                break;
                        case CSQUOTE:
                                USTPUTC(CTLQUOTEMARK, out);
                                state[level].syntax = SQSYNTAX;
                                sqiscstyle = 0;
                                break;
                        case CDQUOTE:
                                USTPUTC(CTLQUOTEMARK, out);
                                state[level].syntax = DQSYNTAX;
                                break;
                        case CENDQUOTE:
                                if (eofmark != NULL && newvarnest == 0)
                                        USTPUTC(c, out);
                                else {
                                        if (state[level].category == TSTATE_VAR_OLD)
                                                USTPUTC(CTLQUOTEEND, out);
                                        state[level].syntax = BASESYNTAX;
                                        quotef++;
                                }
                                break;
                        case CVAR:      /* '$' */
                                PARSESUB();             /* parse substitution */
                                break;
                        case CENDVAR:   /* '}' */
                                if (level > 0 &&
                                    ((state[level].category == TSTATE_VAR_OLD &&
                                      state[level].syntax ==
                                      state[level - 1].syntax) ||
                                    (state[level].category == TSTATE_VAR_NEW &&
                                     state[level].syntax == BASESYNTAX))) {
                                        if (state[level].category == TSTATE_VAR_NEW)
                                                newvarnest--;
                                        level--;
                                        USTPUTC(CTLENDVAR, out);
                                } else {
                                        USTPUTC(c, out);
                                }
                                break;
                        case CLP:       /* '(' in arithmetic */
                                state[level].parenlevel++;
                                USTPUTC(c, out);
                                break;
                        case CRP:       /* ')' in arithmetic */
                                if (state[level].parenlevel > 0) {
                                        USTPUTC(c, out);
                                        --state[level].parenlevel;
                                } else {
                                        if (pgetc_linecont() == ')') {
                                                if (level > 0 &&
                                                    state[level].category == TSTATE_ARITH) {
                                                        level--;
                                                        USTPUTC(CTLENDARI, out);
                                                } else
                                                        USTPUTC(')', out);
                                        } else {
                                                /*
                                                 * unbalanced parens
                                                 *  (don't 2nd guess - no error)
                                                 */
                                                pungetc();
                                                USTPUTC(')', out);
                                        }
                                }
                                break;
                        case CBQUOTE:   /* '`' */
                                out = parsebackq(out, &bqlist, 1,
                                    state[level].syntax == DQSYNTAX &&
                                    (eofmark == NULL || newvarnest > 0),
                                    state[level].syntax == DQSYNTAX || state[level].syntax == ARISYNTAX);
                                break;
                        case CEOF:
                                goto endword;           /* exit outer loop */
                        case CIGN:
                                break;
                        default:
                                if (level == 0)
                                        goto endword;   /* exit outer loop */
                                USTPUTC(c, out);
                        }
                        c = pgetc_macro();
                }
        }
endword:
        if (state[level].syntax == ARISYNTAX)
                synerror("Missing '))'");
        if (state[level].syntax != BASESYNTAX && eofmark == NULL)
                synerror("Unterminated quoted string");
        if (state[level].category == TSTATE_VAR_OLD ||
            state[level].category == TSTATE_VAR_NEW) {
                startlinno = plinno;
                synerror("Missing '}'");
        }
        if (state != state_static)
                parser_temp_free_upto(state);
        USTPUTC('\0', out);
        len = out - stackblock();
        out = stackblock();
        if (eofmark == NULL) {
                if ((c == '>' || c == '<')
                 && quotef == 0
                 && len <= 2
                 && (*out == '\0' || is_digit(*out))) {
                        parseredir(out, c);
                        return lasttoken = TREDIR;
                } else {
                        pungetc();
                }
        }
        quoteflag = quotef;
        backquotelist = bqlist;
        grabstackblock(len);
        wordtext = out;
        return lasttoken = TWORD;
/* end of readtoken routine */


/*
 * Parse a substitution.  At this point, we have read the dollar sign
 * and nothing else.
 */

parsesub: {
        int subtype;
        int typeloc;
        int flags;
        char *p;
        static const char types[] = "}-+?=";
        int linno;
        int length;
        int c1;

        c = pgetc_linecont();
        if (c == '(') { /* $(command) or $((arith)) */
                if (pgetc_linecont() == '(') {
                        PARSEARITH();
                } else {
                        pungetc();
                        out = parsebackq(out, &bqlist, 0,
                            state[level].syntax == DQSYNTAX &&
                            (eofmark == NULL || newvarnest > 0),
                            state[level].syntax == DQSYNTAX ||
                            state[level].syntax == ARISYNTAX);
                }
        } else if (c == '{' || is_name(c) || is_special(c)) {
                USTPUTC(CTLVAR, out);
                typeloc = out - stackblock();
                USTPUTC(VSNORMAL, out);
                subtype = VSNORMAL;
                flags = 0;
                if (c == '{') {
                        c = pgetc_linecont();
                        subtype = 0;
                }
varname:
                if (!is_eof(c) && is_name(c)) {
                        length = 0;
                        do {
                                STPUTC(c, out);
                                c = pgetc_linecont();
                                length++;
                        } while (!is_eof(c) && is_in_name(c));
                        if (length == 6 &&
                            strncmp(out - length, "LINENO", length) == 0) {
                                /* Replace the variable name with the
                                 * current line number. */
                                STADJUST(-6, out);
                                CHECKSTRSPACE(11, out);
                                linno = plinno;
                                if (funclinno != 0)
                                        linno -= funclinno - 1;
                                length = snprintf(out, 11, "%d", linno);
                                if (length > 10)
                                        length = 10;
                                out += length;
                                flags |= VSLINENO;
                        }
                } else if (is_digit(c)) {
                        if (subtype != VSNORMAL) {
                                do {
                                        STPUTC(c, out);
                                        c = pgetc_linecont();
                                } while (is_digit(c));
                        } else {
                                USTPUTC(c, out);
                                c = pgetc_linecont();
                        }
                } else if (is_special(c)) {
                        c1 = c;
                        c = pgetc_linecont();
                        if (subtype == 0 && c1 == '#') {
                                subtype = VSLENGTH;
                                if (strchr(types, c) == NULL && c != ':' &&
                                    c != '#' && c != '%')
                                        goto varname;
                                c1 = c;
                                c = pgetc_linecont();
                                if (c1 != '}' && c == '}') {
                                        pungetc();
                                        c = c1;
                                        goto varname;
                                }
                                pungetc();
                                c = c1;
                                c1 = '#';
                                subtype = 0;
                        }
                        USTPUTC(c1, out);
                } else {
                        subtype = VSERROR;
                        if (c == '}')
                                pungetc();
                        else if (c == '\n' || c == PEOF)
                                synerror("Unexpected end of line in substitution");
                        else if (BASESYNTAX[c] != CCTL)
                                USTPUTC(c, out);
                }
                if (subtype == 0) {
                        switch (c) {
                        case ':':
                                flags |= VSNUL;
                                c = pgetc_linecont();
                                /*FALLTHROUGH*/
                        default:
                                p = strchr(types, c);
                                if (p == NULL) {
                                        if (c == '\n' || c == PEOF)
                                                synerror("Unexpected end of line in substitution");
                                        if (flags == VSNUL)
                                                STPUTC(':', out);
                                        if (BASESYNTAX[c] != CCTL)
                                                STPUTC(c, out);
                                        subtype = VSERROR;
                                } else
                                        subtype = p - types + VSNORMAL;
                                break;
                        case '%':
                        case '#':
                                {
                                        int cc = c;
                                        subtype = c == '#' ? VSTRIMLEFT :
                                                             VSTRIMRIGHT;
                                        c = pgetc_linecont();
                                        if (c == cc)
                                                subtype++;
                                        else
                                                pungetc();
                                        break;
                                }
                        }
                } else if (subtype != VSERROR) {
                        if (subtype == VSLENGTH && c != '}')
                                subtype = VSERROR;
                        pungetc();
                }
                STPUTC('=', out);
                if (state[level].syntax == DQSYNTAX ||
                    state[level].syntax == ARISYNTAX)
                        flags |= VSQUOTE;
                *(stackblock() + typeloc) = subtype | flags;
                if (subtype != VSNORMAL) {
                        if (level + 1 >= maxnest) {
                                maxnest *= 2;
                                if (state == state_static) {
                                        state = parser_temp_alloc(
                                            maxnest * sizeof(*state));
                                        memcpy(state, state_static,
                                            MAXNEST_static * sizeof(*state));
                                } else
                                        state = parser_temp_realloc(state,
                                            maxnest * sizeof(*state));
                        }
                        level++;
                        state[level].parenlevel = 0;
                        if (subtype == VSMINUS || subtype == VSPLUS ||
                            subtype == VSQUESTION || subtype == VSASSIGN) {
                                /*
                                 * For operators that were in the Bourne shell,
                                 * inherit the double-quote state.
                                 */
                                state[level].syntax = state[level - 1].syntax;
                                state[level].category = TSTATE_VAR_OLD;
                        } else {
                                /*
                                 * The other operators take a pattern,
                                 * so go to BASESYNTAX.
                                 * Also, ' and " are now special, even
                                 * in here documents.
                                 */
                                state[level].syntax = BASESYNTAX;
                                state[level].category = TSTATE_VAR_NEW;
                                newvarnest++;
                        }
                }
        } else if (c == '\'' && state[level].syntax == BASESYNTAX) {
                /* $'cstylequotes' */
                USTPUTC(CTLQUOTEMARK, out);
                state[level].syntax = SQSYNTAX;
                sqiscstyle = 1;
        } else {
                USTPUTC('$', out);
                pungetc();
        }
        goto parsesub_return;
}


/*
 * Parse an arithmetic expansion (indicate start of one and set state)
 */
parsearith: {

        if (level + 1 >= maxnest) {
                maxnest *= 2;
                if (state == state_static) {
                        state = parser_temp_alloc(
                            maxnest * sizeof(*state));
                        memcpy(state, state_static,
                            MAXNEST_static * sizeof(*state));
                } else
                        state = parser_temp_realloc(state,
                            maxnest * sizeof(*state));
        }
        level++;
        state[level].syntax = ARISYNTAX;
        state[level].parenlevel = 0;
        state[level].category = TSTATE_ARITH;
        USTPUTC(CTLARI, out);
        if (state[level - 1].syntax == DQSYNTAX)
                USTPUTC('"',out);
        else
                USTPUTC(' ',out);
        goto parsearith_return;
}

} /* end of readtoken */


/*
 * Returns true if the text contains nothing to expand (no dollar signs
 * or backquotes).
 */

static int
noexpand(char *text)
{
        char *p;
        char c;

        p = text;
        while ((c = *p++) != '\0') {
                if ( c == CTLQUOTEMARK)
                        continue;
                if (c == CTLESC)
                        p++;
                else if (BASESYNTAX[(int)c] == CCTL)
                        return 0;
        }
        return 1;
}


/*
 * Return true if the argument is a legal variable name (a letter or
 * underscore followed by zero or more letters, underscores, and digits).
 */

int
goodname(const char *name)
{
        const char *p;

        p = name;
        if (! is_name(*p))
                return 0;
        while (*++p) {
                if (! is_in_name(*p))
                        return 0;
        }
        return 1;
}


int
isassignment(const char *p)
{
        if (!is_name(*p))
                return 0;
        p++;
        for (;;) {
                if (*p == '=')
                        return 1;
                else if (!is_in_name(*p))
                        return 0;
                p++;
        }
}


static void
consumetoken(int token)
{
        if (readtoken() != token)
                synexpect(token);
}


/*
 * Called when an unexpected token is read during the parse.  The argument
 * is the token that is expected, or -1 if more than one type of token can
 * occur at this point.
 */

static void
synexpect(int token)
{
        char msg[64];

        if (token >= 0) {
                fmtstr(msg, 64, "%s unexpected (expecting %s)",
                        tokname[lasttoken], tokname[token]);
        } else {
                fmtstr(msg, 64, "%s unexpected", tokname[lasttoken]);
        }
        synerror(msg);
}


static void
synerror(const char *msg)
{
        if (commandname)
                outfmt(out2, "%s: %d: ", commandname, startlinno);
        else if (arg0)
                outfmt(out2, "%s: ", arg0);
        outfmt(out2, "Syntax error: %s\n", msg);
        error((char *)NULL);
}

static void
setprompt(int which)
{
        whichprompt = which;
        if (which == 0)
                return;

#ifndef NO_HISTORY
        if (!el)
#endif
        {
                out2str(getprompt(NULL));
                flushout(out2);
        }
}

static int
pgetc_linecont(void)
{
        int c;

        while ((c = pgetc_macro()) == '\\') {
                c = pgetc();
                if (c == '\n') {
                        plinno++;
                        if (doprompt)
                                setprompt(2);
                        else
                                setprompt(0);
                } else {
                        pungetc();
                        /* Allow the backslash to be pushed back. */
                        pushstring("\\", 1, NULL);
                        return (pgetc());
                }
        }
        return (c);
}


static struct passwd *
getpwlogin(void)
{
        const char *login;

        login = getlogin();
        if (login == NULL)
                return (NULL);

        return (getpwnam(login));
}


static void
getusername(char *name, size_t namelen)
{
        static char cached_name[MAXLOGNAME];
        struct passwd *pw;
        uid_t euid;

        if (cached_name[0] == '\0') {
                euid = geteuid();

                /*
                 * Handle the case when there is more than one
                 * login with the same UID, or when the login
                 * returned by getlogin(2) does no longer match
                 * the current UID.
                 */
                pw = getpwlogin();
                if (pw == NULL || pw->pw_uid != euid)
                        pw = getpwuid(euid);

                if (pw != NULL) {
                        strlcpy(cached_name, pw->pw_name,
                            sizeof(cached_name));
                } else {
                        snprintf(cached_name, sizeof(cached_name),
                            "%u", euid);
                }
        }

        strlcpy(name, cached_name, namelen);
}


/*
 * called by editline -- any expansions to the prompt
 *    should be added here.
 */
char *
getprompt(void *unused __unused)
{
        static char ps[PROMPTLEN];
        const char *fmt;
        const char *home;
        const char *pwd;
        size_t homelen;
        int i, trim;
        static char internal_error[] = "??";

        /*
         * Select prompt format.
         */
        switch (whichprompt) {
        case 0:
                fmt = "";
                break;
        case 1:
                fmt = ps1val();
                break;
        case 2:
                fmt = ps2val();
                break;
        default:
                return internal_error;
        }

        /*
         * Format prompt string.
         */
        for (i = 0; (i < PROMPTLEN - 1) && (*fmt != '\0'); i++, fmt++) {
                if (*fmt == '$') {
                        const char *varname_start, *varname_end, *value;
                        char varname[256];
                        int namelen, braced = 0;

                        fmt++;  /* Skip the '$' */

                        /* Check for ${VAR} syntax */
                        if (*fmt == '{') {
                                braced = 1;
                                fmt++;
                        }

                        varname_start = fmt;

                        /* Extract variable name */
                        if (is_digit(*fmt)) {
                                /* Positional parameter: $0, $1, etc. */
                                fmt++;
                                varname_end = fmt;
                        } else if (is_special(*fmt)) {
                                /* Special parameter: $?, $!, $$, etc. */
                                fmt++;
                                varname_end = fmt;
                        } else if (is_name(*fmt)) {
                                /* Regular variable name */
                                do
                                        fmt++;
                                while (is_in_name(*fmt));
                                varname_end = fmt;
                        } else {
                                /*
                                 * Not a valid variable reference.
                                 * Output literal '$'.
                                 */
                                ps[i] = '$';
                                if (braced && i < PROMPTLEN - 2)
                                        ps[++i] = '{';
                                fmt = varname_start - 1;
                                continue;
                        }

                        namelen = varname_end - varname_start;
                        if (namelen == 0 || namelen >= (int)sizeof(varname)) {
                                /* Invalid or too long, output literal */
                                ps[i] = '$';
                                fmt = varname_start - 1;
                                continue;
                        }

                        /* Copy variable name */
                        memcpy(varname, varname_start, namelen);
                        varname[namelen] = '\0';

                        /* Handle closing brace for ${VAR} */
                        if (braced) {
                                if (*fmt == '}') {
                                        fmt++;
                                } else {
                                        /* Missing closing brace, treat as literal */
                                        ps[i] = '$';
                                        if (i < PROMPTLEN - 2)
                                                ps[++i] = '{';
                                        fmt = varname_start - 1;
                                        continue;
                                }
                        }

                        /* Look up the variable */
                        if (namelen == 1 && is_digit(*varname)) {
                                /* Positional parameters - check digits FIRST */
                                int num = *varname - '0';
                                if (num == 0)
                                        value = arg0 ? arg0 : "";
                                else if (num > 0 && num <= shellparam.nparam)
                                        value = shellparam.p[num - 1];
                                else
                                        value = "";
                        } else if (namelen == 1 && is_special(*varname)) {
                                /* Special parameters */
                                char valbuf[20];
                                int num;

                                switch (*varname) {
                                case '$':
                                        num = rootpid;
                                        break;
                                case '?':
                                        num = exitstatus;
                                        break;
                                case '#':
                                        num = shellparam.nparam;
                                        break;
                                case '!':
                                        num = backgndpidval();
                                        break;
                                default:
                                        num = 0;
                                        break;
                                }
                                snprintf(valbuf, sizeof(valbuf), "%d", num);
                                value = valbuf;
                        } else {
                                /* Regular variables */
                                value = lookupvar(varname);
                                if (value == NULL)
                                        value = "";
                        }

                        /* Copy value to output, respecting buffer size */
                        while (*value != '\0' && i < PROMPTLEN - 1) {
                                ps[i++] = *value++;
                        }

                        /*
                         * Adjust fmt and i for the loop increment.
                         * fmt will be incremented by the for loop,
                         * so position it one before where we want.
                         */
                        fmt--;
                        i--;
                        continue;
                } else if (*fmt != '\\') {
                        ps[i] = *fmt;
                        continue;
                }

                switch (*++fmt) {

                /*
                 * Non-printing sequence begin and end.
                 */
                case '[':
                case ']':
                        ps[i] = '\001';
                        break;

                /*
                 * Literal \ and some ASCII characters:
                 * \a   BEL
                 * \e   ESC
                 * \r   CR
                 */
                case '\\':
                case 'a':
                case 'e':
                case 'r':
                        if (*fmt == 'a')
                                ps[i] = '\007';
                        else if (*fmt == 'e')
                                ps[i] = '\033';
                        else if (*fmt == 'r')
                                ps[i] = '\r';
                        else
                                ps[i] = '\\';
                        break;

                /*
                 * CRLF sequence
                 */
                case 'n':
                        if (i < PROMPTLEN - 3) {
                                ps[i++] = '\r';
                                ps[i] = '\n';
                        }
                        break;

                /*
                 * Print the current time as per provided strftime format.
                 */
                case 'D': {
                        char tfmt[128] = "%X"; /* \D{} means %X. */
                        struct tm *now;

                        if (fmt[1] != '{') {
                                /*
                                 * "\D" but not "\D{", so treat the '\'
                                 * literally and rewind fmt to treat 'D'
                                 * literally next iteration.
                                 */
                                ps[i] = '\\';
                                fmt--;
                                break;
                        }
                        fmt += 2; /* Consume "D{". */
                        if (fmt[0] != '}') {
                                char *end;

                                end = memccpy(tfmt, fmt, '}', sizeof(tfmt));
                                if (end == NULL) {
                                        /*
                                         * Format too long or no '}', so
                                         * ignore "\D{" altogether.
                                         * The loop will do i++, but nothing
                                         * was written to ps, so do i-- here.
                                         * Rewind fmt for similar reason.
                                         */
                                        i--;
                                        fmt--;
                                        break;
                                }
                                *--end = '\0'; /* Ignore the copy of '}'. */
                                fmt += end - tfmt;
                        }
                        now = localtime(&(time_t){time(NULL)});
                        i += strftime(&ps[i], PROMPTLEN - i - 1, tfmt, now);
                        i--; /* The loop will do i++. */
                        break;
                }

                /*
                 * Hostname.
                 *
                 * \h specifies just the local hostname,
                 * \H specifies fully-qualified hostname.
                 */
                case 'h':
                case 'H':
                        ps[i] = '\0';
                        gethostname(&ps[i], PROMPTLEN - i - 1);
                        ps[PROMPTLEN - 1] = '\0';
                        /* Skip to end of hostname. */
                        trim = (*fmt == 'h') ? '.' : '\0';
                        while ((ps[i] != '\0') && (ps[i] != trim))
                                i++;
                        --i;
                        break;

                /*
                 * User name.
                 */
                case 'u':
                        ps[i] = '\0';
                        getusername(&ps[i], PROMPTLEN - i);
                        /* Skip to end of username. */
                        while (ps[i + 1] != '\0')
                                i++;
                        break;

                /*
                 * Working directory.
                 *
                 * \W specifies just the final component,
                 * \w specifies the entire path.
                 */
                case 'W':
                case 'w':
                        pwd = lookupvar("PWD");
                        if (pwd == NULL || *pwd == '\0')
                                pwd = "?";
                        if (*fmt == 'W' &&
                            *pwd == '/' && pwd[1] != '\0')
                                strlcpy(&ps[i], strrchr(pwd, '/') + 1,
                                    PROMPTLEN - i);
                        else {
                                home = lookupvar("HOME");
                                if (home != NULL)
                                        homelen = strlen(home);
                                if (home != NULL &&
                                    strcmp(home, "/") != 0 &&
                                    strncmp(pwd, home, homelen) == 0 &&
                                    (pwd[homelen] == '/' ||
                                    pwd[homelen] == '\0')) {
                                        strlcpy(&ps[i], "~",
                                            PROMPTLEN - i);
                                        strlcpy(&ps[i + 1],
                                            pwd + homelen,
                                            PROMPTLEN - i - 1);
                                } else {
                                        strlcpy(&ps[i], pwd, PROMPTLEN - i);
                                }
                        }
                        /* Skip to end of path. */
                        while (ps[i + 1] != '\0')
                                i++;
                        break;

                /*
                 * Superuser status.
                 *
                 * '$' for normal users, '#' for root.
                 */
                case '$':
                        ps[i] = (geteuid() != 0) ? '$' : '#';
                        break;

                /*
                 * Emit unrecognized formats verbatim.
                 */
                default:
                        ps[i] = '\\';
                        if (i < PROMPTLEN - 2)
                                ps[++i] = *fmt;
                        break;
                }

        }
        ps[i] = '\0';
        return (ps);
}


const char *
expandstr(const char *ps)
{
        union node n;
        struct jmploc jmploc;
        struct jmploc *const savehandler = handler;
        const int saveprompt = doprompt;
        struct parsefile *const savetopfile = getcurrentfile();
        struct parser_temp *const saveparser_temp = parser_temp;
        const char *result = NULL;

        if (!setjmp(jmploc.loc)) {
                handler = &jmploc;
                parser_temp = NULL;
                setinputstring(ps, 1);
                doprompt = 0;
                readtoken1(pgetc(), DQSYNTAX, NOEOFMARK, 0);
                if (backquotelist != NULL)
                        error("Command substitution not allowed here");

                n.narg.type = NARG;
                n.narg.next = NULL;
                n.narg.text = wordtext;
                n.narg.backquote = backquotelist;

                expandarg(&n, NULL, 0);
                result = stackblock();
                INTOFF;
        }
        handler = savehandler;
        doprompt = saveprompt;
        popfilesupto(savetopfile);
        if (parser_temp != saveparser_temp) {
                parser_temp_free_all();
                parser_temp = saveparser_temp;
        }
        if (result != NULL) {
                INTON;
        } else if (exception == EXINT)
                raise(SIGINT);
        return result;
}