/*      $NetBSD: exec.c,v 1.61 2026/05/28 10:07:58 kre Exp $    */

/*-
 * 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/cdefs.h>
#ifndef lint
#if 0
static char sccsid[] = "@(#)exec.c      8.4 (Berkeley) 6/8/95";
#else
__RCSID("$NetBSD: exec.c,v 1.61 2026/05/28 10:07:58 kre Exp $");
#endif
#endif /* not lint */

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>

/*
 * When commands are first encountered, they are entered in a hash table.
 * This ensures that a full path search will not have to be done for them
 * on each invocation.
 *
 * We should investigate converting to a linear search, even though that
 * would make the command name "hash" a misnomer.
 */

#include "shell.h"
#include "main.h"
#include "nodes.h"
#include "parser.h"
#include "redir.h"
#include "eval.h"
#include "exec.h"
#include "builtins.h"
#include "var.h"
#include "options.h"
#include "input.h"
#include "output.h"
#include "syntax.h"
#include "memalloc.h"
#include "error.h"
#include "init.h"
#include "mystring.h"
#include "show.h"
#include "jobs.h"
#include "alias.h"


#define CMDTABLESIZE 31         /* should be prime */
#define ARB 1                   /* actual size determined at run time */



struct tblentry {
        struct tblentry *next;  /* next entry in hash chain */
        union param param;      /* definition of builtin function */
        short cmdtype;          /* index identifying command */
        char rehash;            /* if set, cd done since entry created */
        char fn_ln1;            /* for functions, LINENO from 1 */
        int lineno;             /* for functions abs LINENO of definition */
        char cmdname[ARB];      /* name of command */
};


STATIC struct tblentry *cmdtable[CMDTABLESIZE];
STATIC int builtinloc = -1;             /* index in path of %builtin, or -1 */
int exerrno = 0;                        /* Last exec error */


STATIC void tryexec(char *, char **, char **, int);
STATIC void printentry(struct tblentry *, int);
STATIC void addcmdentry(char *, struct cmdentry *);
STATIC void clearcmdentry(int);
STATIC struct tblentry *cmdlookup(const char *, int);
STATIC void delete_cmd_entry(void);

#ifndef BSD
STATIC void execinterp(char **, char **);
#endif


extern const char *const parsekwd[];

/*
 * Exec a program.  Never returns.  If you change this routine, you may
 * have to change the find_command routine as well.
 */

void
shellexec(char **argv, char **envp, const char *path, int idx, int vforked)
{
        char *cmdname;
        int e, action;
        struct stat statb;

        action = E_EXEC;

        if (strchr(argv[0], '/') != NULL) {
                tryexec(argv[0], argv, envp, vforked);
                e = errno;
                if (e == EACCES && stat(argv[0], &statb) == -1)
                        action = E_OPEN;
        } else {
                e = ENOENT;
                while ((cmdname = padvance(&path, argv[0], 1)) != NULL) {
                        if (--idx < 0 && pathopt == NULL) {
                                /*
                                 * tryexec() does not return if it works.
                                 */
                                tryexec(cmdname, argv, envp, vforked);
                                /*
                                 * If do not already have a meaningful error
                                 * from earlier in the PATH, examine this one
                                 * if it is a simple "not found", just keep
                                 * searching.
                                 */
                                if (e == ENOENT &&
                                    errno != ENOENT && errno != ENOTDIR) {
                                        /*
                                         * If the error is from permission
                                         * denied on the path search (a call
                                         * to stat() also fails) ignore it
                                         * (just continue with the search)
                                         * If it is EACCESS and the file exists
                                         * (the stat succeeds) that means no
                                         * 'x' perm on the file itself, which
                                         * is a meaningful error, this will be
                                         * the one reported if no later PATH
                                         * element actually succeeds.
                                         */
                                        if (errno == EACCES) {
                                                if (stat(cmdname, &statb) != -1)
                                                        e = EACCES;
                                        } else {
                                                /*
                                                 * any other error we will
                                                 * remember as the significant
                                                 * error
                                                 */
                                                e = errno;
                                        }
                                }
                        }
                        stunalloc(cmdname);
                }
        }

        /* Map to POSIX errors */
        switch (e) {
        case EACCES:    /* particularly this (unless no search perm) */
                if (action == E_OPEN) {
                        /*
                         * this is an EACCES from namei
                         * ie: no permission to search the path given
                         * rather than an EACCESS from exec
                         * ie: no 'x' bit on the file to be executed
                         */
                        exerrno = 127;
                        break;
                }
                /* FALLTHROUGH */
        case EINVAL:    /* also explicitly these */
        case ENOEXEC:
        default:        /* and anything else */
                exerrno = 126;
                break;

        case ENOENT:    /* these are the "pathname lookup failed" errors */
        case ELOOP:
        case ENOTDIR:
        case ENAMETOOLONG:
                exerrno = 127;
                break;
        }
        CTRACE(DBG_ERRS|DBG_CMDS|DBG_EVAL,
            ("shellexec failed for %s, errno %d, vforked %d, suppressint %d\n",
                argv[0], e, vforked, suppressint));
        exerror(EXEXEC, "%s: %s", argv[0], errmsg(e, action));
        /* NOTREACHED */
}


STATIC void
tryexec(char *cmd, char **argv, char **envp, int vforked)
{
        int e;
#ifndef BSD
        char *p;
#endif

#ifdef SYSV
        do {
                execve(cmd, argv, envp);
        } while (errno == EINTR);
#else
        execve(cmd, argv, envp);
#endif
        e = errno;
        if (e == ENOEXEC) {
                if (vforked) {
                        /* We are currently vfork(2)ed, so raise an
                         * exception, and evalcommand will try again
                         * with a normal fork(2).
                         */
                        exraise(EXSHELLPROC);
                }
#ifdef DEBUG
                VTRACE(DBG_CMDS, ("execve(cmd=%s) returned ENOEXEC\n", cmd));
#endif
                initshellproc();
                setinputfile(cmd, 0);
                commandname = arg0 = savestr(argv[0]);
#ifndef BSD
                pgetc(); pungetc();             /* fill up input buffer */
                p = parsenextc;
                if (parsenleft > 2 && p[0] == '#' && p[1] == '!') {
                        argv[0] = cmd;
                        execinterp(argv, envp);
                }
#endif
                setparam(argv + 1);
                exraise(EXSHELLPROC);
        }
        errno = e;
}


#ifndef BSD
/*
 * Execute an interpreter introduced by "#!", for systems where this
 * feature has not been built into the kernel.  If the interpreter is
 * the shell, return (effectively ignoring the "#!").  If the execution
 * of the interpreter fails, exit.
 *
 * This code peeks inside the input buffer in order to avoid actually
 * reading any input.  It would benefit from a rewrite.
 */

#define NEWARGS 5

STATIC void
execinterp(char **argv, char **envp)
{
        int n;
        char *inp;
        char *outp;
        char c;
        char *p;
        char **ap;
        char *newargs[NEWARGS];
        int i;
        char **ap2;
        char **new;

        n = parsenleft - 2;
        inp = parsenextc + 2;
        ap = newargs;
        for (;;) {
                while (--n >= 0 && (*inp == ' ' || *inp == '\t'))
                        inp++;
                if (n < 0)
                        goto bad;
                if ((c = *inp++) == '\n')
                        break;
                if (ap == &newargs[NEWARGS])
bad:              error("Bad #! line");
                STARTSTACKSTR(outp);
                do {
                        STPUTC(c, outp);
                } while (--n >= 0 && (c = *inp++) != ' ' && c != '\t' && c != '\n');
                STPUTC('\0', outp);
                n++, inp--;
                *ap++ = grabstackstr(outp);
        }
        if (ap == newargs + 1) {        /* if no args, maybe no exec is needed */
                p = newargs[0];
                for (;;) {
                        if (equal(p, "sh") || equal(p, "ash")) {
                                return;
                        }
                        while (*p != '/') {
                                if (*p == '\0')
                                        goto break2;
                                p++;
                        }
                        p++;
                }
break2:;
        }
        i = (char *)ap - (char *)newargs;               /* size in bytes */
        if (i == 0)
                error("Bad #! line");
        for (ap2 = argv ; *ap2++ != NULL ; );
        new = ckmalloc(i + ((char *)ap2 - (char *)argv));
        ap = newargs, ap2 = new;
        while ((i -= sizeof (char **)) >= 0)
                *ap2++ = *ap++;
        ap = argv;
        while (*ap2++ = *ap++);
        shellexec(new, envp, pathval(), 0);
        /* NOTREACHED */
}
#endif



/*
 * Do a path search.  The variable path (passed by reference) should be
 * set to the start of the path before the first call; padvance will update
 * this value as it proceeds.  Successive calls to padvance will return
 * the possible path expansions in sequence.  If an option (indicated by
 * a percent sign) appears in the path entry then the global variable
 * pathopt will be set to point to it; otherwise pathopt will be set to
 * NULL.
 */

const char *pathopt;

char *
padvance(const char **path, const char *name, int magic_percent)
{
        const char *p;
        char *q;
        const char *start;
        int len;

        if (*path == NULL)
                return NULL;
        if (magic_percent)
                magic_percent = '%';

        start = *path;
        for (p = start ; *p && *p != ':' && *p != magic_percent ; p++)
                ;
        len = p - start + strlen(name) + 2;     /* "2" is for '/' and '\0' */
        while (stackblocksize() < len)
                growstackblock();
        q = stackblock();
        if (p != start) {
                memcpy(q, start, p - start);
                q += p - start;
                if (q[-1] != '/')
                        *q++ = '/';
        }
        strcpy(q, name);
        pathopt = NULL;
        if (*p == magic_percent) {
                pathopt = ++p;
                while (*p && *p != ':')
                        p++;
        }
        if (*p == ':')
                *path = p + 1;
        else
                *path = NULL;
        return grabstackstr(q + strlen(name) + 1);
}


/*** Command hashing code ***/


int
hashcmd(int argc, char **argv)
{
        struct tblentry **pp;
        struct tblentry *cmdp;
        int c;
        struct cmdentry entry;
        char *name;
        int allopt=0, bopt=0, fopt=0, ropt=0, sopt=0, uopt=0, verbose=0;
        int errs=1, emsg=DO_ERR;
        int status = 0;

        while ((c = nextopt("bcefqrsuv")) != '\0')
                switch (c) {
                case 'b':       bopt = 1;       break;
                case 'c':       uopt = 1;       break;  /* c == u */
                case 'e':       errs = 0;       break;
                case 'f':       fopt = 1;       break;
                case 'q':       emsg = 0;       break;
                case 'r':       ropt = 1;       break;
                case 's':       sopt = 1;       break;
                case 'u':       uopt = 1;       break;
                case 'v':       verbose = 1;    break;
                }

        if (!errs)
                emsg ^= DO_ERR;

        if (ropt)
                clearcmdentry(0);

        if (bopt == 0 && fopt == 0 && sopt == 0 && uopt == 0)
                allopt = bopt = fopt = sopt = uopt = 1;

        if (*argptr == NULL) {
                for (pp = cmdtable ; pp < &cmdtable[CMDTABLESIZE] ; pp++) {
                        for (cmdp = *pp ; cmdp ; cmdp = cmdp->next) {
                                switch (cmdp->cmdtype) {
                                case CMDNORMAL:
                                        if (!uopt)
                                                continue;
                                        break;
                                case CMDBUILTIN:
                                        if (!bopt)
                                                continue;
                                        break;
                                case CMDSPLBLTIN:
                                        if (!sopt)
                                                continue;
                                        break;
                                case CMDFUNCTION:
                                        if (!fopt)
                                                continue;
                                        break;
                                default:        /* never happens */
                                        continue;
                                }
                                if (!allopt || verbose ||
                                    cmdp->cmdtype == CMDNORMAL)
                                        printentry(cmdp, verbose);
                        }
                }
                flushout(out1);
                if (io_err(out1)) {
                        out2str("hash: I/O error writing to standard output\n");
                        return 1;
                }
                return 0;
        }

        while ((name = *argptr++) != NULL) {
                if ((cmdp = cmdlookup(name, 0)) != NULL) {
                        switch (cmdp->cmdtype) {
                        case CMDNORMAL:
                                if (!uopt)
                                        continue;
                                delete_cmd_entry();
                                break;
                        case CMDBUILTIN:
                                if (!bopt)
                                        continue;
                                if (builtinloc >= 0)
                                        delete_cmd_entry();
                                break;
                        case CMDSPLBLTIN:
                                if (!sopt)
                                        continue;
                                break;
                        case CMDFUNCTION:
                                if (!fopt)
                                        continue;
                                break;
                        }
                }
                find_command(name, &entry, emsg, pathval());
                if (errs && entry.cmdtype == CMDUNKNOWN)
                        status = 1;
                if (verbose) {
                        if (entry.cmdtype != CMDUNKNOWN) {      /* if no error msg */
                                cmdp = cmdlookup(name, 0);
                                if (cmdp != NULL)
                                        printentry(cmdp, verbose);
                        }
                        flushall();
                }
        }
        return status;
}

STATIC void
printentry(struct tblentry *cmdp, int verbose)
{
        int idx;
        const char *path;
        char *name;

        switch (cmdp->cmdtype) {
        case CMDNORMAL:
                idx = cmdp->param.index;
                path = pathval();
                do {
                        name = padvance(&path, cmdp->cmdname, 1);
                        stunalloc(name);
                } while (--idx >= 0);
                if (verbose)
                        out1fmt("Command from PATH[%d]: ",
                            cmdp->param.index);
                out1str(name);
                break;
        case CMDSPLBLTIN:
                if (verbose)
                        out1str("special ");
                /* FALLTHROUGH */
        case CMDBUILTIN:
                if (verbose)
                        out1str("builtin ");
                out1fmt("%s", cmdp->cmdname);
                break;
        case CMDFUNCTION:
                if (verbose)
                        out1str("function ");
                out1fmt("%s", cmdp->cmdname);
                if (verbose) {
                        struct procstat ps;

                        INTOFF;
                        commandtext(&ps, getfuncnode(cmdp->param.func));
                        INTON;
                        out1str("() { ");
                        out1str(ps.cmd);
                        out1str("; }");
                }
                break;
        default:
                error("internal error: %s cmdtype %d",
                    cmdp->cmdname, cmdp->cmdtype);
        }
        if (cmdp->rehash)
                out1c('*');
        out1c('\n');
}



/*
 * Resolve a command name.  If you change this routine, you may have to
 * change the shellexec routine as well.
 */

void
find_command(char *name, struct cmdentry *entry, int act, const char *path)
{
        struct tblentry *cmdp, loc_cmd;
        int idx;
        int prev;
        char *fullname;
        struct stat statb;
        int e;
        int (*bltin)(int,char **);

        /* If name contains a slash, don't use PATH or hash table */
        if (strchr(name, '/') != NULL) {
                if (act & DO_ABS) {
                        while (stat(name, &statb) < 0) {
#ifdef SYSV
                                if (errno == EINTR)
                                        continue;
#endif
                                if (errno != ENOENT && errno != ENOTDIR)
                                        e = errno;
                                entry->cmdtype = CMDUNKNOWN;
                                entry->u.index = -1;
                                return;
                        }
                        entry->cmdtype = CMDNORMAL;
                        entry->u.index = -1;
                        return;
                }
                entry->cmdtype = CMDNORMAL;
                entry->u.index = 0;
                return;
        }

        if (path != pathval())
                act |= DO_ALTPATH;

        if (act & DO_ALTPATH && strstr(path, "%builtin") != NULL)
                act |= DO_ALTBLTIN;

        /* If name is in the table, check answer will be ok */
        if ((cmdp = cmdlookup(name, 0)) != NULL) {
                switch (cmdp->cmdtype) {
                case CMDNORMAL:
                        if (act & DO_ALTPATH)
                                cmdp = NULL;
                        break;
                case CMDFUNCTION:
                        if (act & DO_NOFUNC)
                                cmdp = NULL;
                        break;
                case CMDBUILTIN:
                        if ((act & DO_ALTBLTIN) || builtinloc >= 0)
                                cmdp = NULL;
                        break;
                }
                /* if not invalidated by cd, we're done */
                if (cmdp != NULL && cmdp->rehash == 0)
                        goto success;
        }

        /* If %builtin not in path, check for builtin next */
        if ((act & DO_ALTPATH ? !(act & DO_ALTBLTIN) : builtinloc < 0) &&
            (bltin = find_builtin(name)) != 0)
                goto builtin_success;

        /* We have to search path. */
        prev = -1;              /* where to start */
        if (cmdp) {             /* doing a rehash */
                if (cmdp->cmdtype == CMDBUILTIN)
                        prev = builtinloc;
                else
                        prev = cmdp->param.index;
        }

        e = ENOENT;
        idx = -1;
loop:
        while ((fullname = padvance(&path, name, 1)) != NULL) {
                stunalloc(fullname);
                idx++;
                if (pathopt) {
                        if (prefix("builtin", pathopt)) {
                                if ((bltin = find_builtin(name)) == 0)
                                        goto loop;
                                goto builtin_success;
                        } else if (prefix("func", pathopt)) {
                                /* handled below */
                        } else {
                                /* ignore unimplemented options */
                                goto loop;
                        }
                }
                /* if rehash, don't redo absolute path names */
                if (fullname[0] == '/' && idx <= prev) {
                        if (idx < prev)
                                goto loop;
                        VTRACE(DBG_CMDS, ("searchexec \"%s\": no change\n",
                            name));
                        goto success;
                }
                while (stat(fullname, &statb) < 0) {
#ifdef SYSV
                        if (errno == EINTR)
                                continue;
#endif
                        if (errno != ENOENT && errno != ENOTDIR)
                                e = errno;
                        goto loop;
                }
                e = EACCES;     /* if we fail, this will be the error */
                if (!S_ISREG(statb.st_mode))
                        goto loop;
                if (pathopt) {          /* this is a %func directory */
                        char *endname;

                        if (act & DO_NOFUNC)
                                goto loop;
                        endname = fullname + strlen(fullname) + 1;
                        grabstackstr(endname);
                        readcmdfile(fullname);
                        if ((cmdp = cmdlookup(name, 0)) == NULL ||
                            cmdp->cmdtype != CMDFUNCTION)
                                error("%s not defined in %s", name, fullname);
                        ungrabstackstr(fullname, endname);
                        goto success;
                }
#ifdef notdef
                /* XXX this code stops root executing stuff, and is buggy
                   if you need a group from the group list. */
                if (statb.st_uid == geteuid()) {
                        if ((statb.st_mode & 0100) == 0)
                                goto loop;
                } else if (statb.st_gid == getegid()) {
                        if ((statb.st_mode & 010) == 0)
                                goto loop;
                } else {
                        if ((statb.st_mode & 01) == 0)
                                goto loop;
                }
#endif
                VTRACE(DBG_CMDS, ("searchexec \"%s\" returns \"%s\"\n", name,
                    fullname));
                INTOFF;
                if (act & DO_ALTPATH) {
                /*
                 * this should be a grabstackstr() but is not needed:
                 * fullname is no longer needed for anything
                        stalloc(strlen(fullname) + 1);
                 */
                        cmdp = &loc_cmd;
                } else
                        cmdp = cmdlookup(name, 1);

                if (cmdp->cmdtype == CMDFUNCTION)
                        cmdp = &loc_cmd;

                cmdp->cmdtype = CMDNORMAL;
                cmdp->param.index = idx;
                INTON;
                goto success;
        }

        /* We failed.  If there was an entry for this command, delete it */
        if (cmdp)
                delete_cmd_entry();
        if (act & DO_ERR)
                outfmt(out2, "%s: %s\n", name, errmsg(e, E_EXEC));
        entry->cmdtype = CMDUNKNOWN;
        entry->u.index = idx + 1;
        return;

builtin_success:
        INTOFF;
        if (act & DO_ALTPATH)
                cmdp = &loc_cmd;
        else
                cmdp = cmdlookup(name, 1);
        if (cmdp->cmdtype == CMDFUNCTION)
                /* DO_NOFUNC must have been set */
                cmdp = &loc_cmd;
        cmdp->cmdtype = CMDBUILTIN;
        cmdp->param.bltin = bltin;
        INTON;
success:
        if (cmdp) {
                cmdp->rehash = 0;
                entry->cmdtype = cmdp->cmdtype;
                entry->lineno = cmdp->lineno;
                entry->lno_frel = cmdp->fn_ln1;
                entry->u = cmdp->param;
        } else {
                entry->cmdtype = CMDUNKNOWN;
                entry->u.index = -1;
        }
}



/*
 * Search the table of builtin commands.
 */

int
(*find_builtin(char *name))(int, char **)
{
        const struct builtincmd *bp;

        for (bp = builtincmd ; bp->name ; bp++) {
                if (*bp->name == *name
                    && (*name == '%' || equal(bp->name, name)))
                        return bp->builtin;
        }
        return 0;
}

int
(*find_splbltin(char *name))(int, char **)
{
        const struct builtincmd *bp;

        for (bp = splbltincmd ; bp->name ; bp++) {
                if (*bp->name == *name && equal(bp->name, name))
                        return bp->builtin;
        }
        return 0;
}

/*
 * At shell startup put special builtins into hash table.
 * ensures they are executed first (see posix).
 * We stop functions being added with the same name
 * (as they are impossible to call)
 */

void
hash_special_builtins(void)
{
        const struct builtincmd *bp;
        struct tblentry *cmdp;

        for (bp = splbltincmd ; bp->name ; bp++) {
                cmdp = cmdlookup(bp->name, 1);
                cmdp->cmdtype = CMDSPLBLTIN;
                cmdp->param.bltin = bp->builtin;
        }
}



/*
 * Called when a cd is done.  Marks all commands so the next time they
 * are executed they will be rehashed.
 */

void
hashcd(void)
{
        struct tblentry **pp;
        struct tblentry *cmdp;

        for (pp = cmdtable ; pp < &cmdtable[CMDTABLESIZE] ; pp++) {
                for (cmdp = *pp ; cmdp ; cmdp = cmdp->next) {
                        if (cmdp->cmdtype == CMDNORMAL
                         || (cmdp->cmdtype == CMDBUILTIN && builtinloc >= 0))
                                cmdp->rehash = 1;
                }
        }
}



/*
 * Fix command hash table when PATH changed.
 * Called before PATH is changed.  The argument is the new value of PATH;
 * pathval() still returns the old value at this point.
 * Called with interrupts off.
 */

void
changepath(const char *new, int flags __unused, struct var *vp __unused)
{
        const char *old;
        int idx;
        int firstchange;
        int bltin;

        old = pathval();
        firstchange = 9999;     /* assume no change */
        idx = 0;
        bltin = -1;
        for (;;) {
                if (*old != *new) {
                        firstchange = idx;
                        if ((*old == '\0' && *new == ':')
                         || (*old == ':' && *new == '\0'))
                                firstchange++;
                        old = new;      /* ignore subsequent differences */
                }
                if (*new == '\0')
                        break;
                if (*new == '%' && bltin < 0 && prefix("builtin", new + 1))
                        bltin = idx;
                if (*new == ':') {
                        idx++;
                }
                new++, old++;
        }
        if (builtinloc < 0 && bltin >= 0)
                builtinloc = bltin;             /* zap builtins */
        if (builtinloc >= 0 && bltin < 0)
                firstchange = 0;
        clearcmdentry(firstchange);
        builtinloc = bltin;
}


/*
 * Clear out command entries.  The argument specifies the first entry in
 * PATH which has changed.
 */

STATIC void
clearcmdentry(int firstchange)
{
        struct tblentry **tblp;
        struct tblentry **pp;
        struct tblentry *cmdp;

        INTOFF;
        for (tblp = cmdtable ; tblp < &cmdtable[CMDTABLESIZE] ; tblp++) {
                pp = tblp;
                while ((cmdp = *pp) != NULL) {
                        if ((cmdp->cmdtype == CMDNORMAL &&
                             cmdp->param.index >= firstchange)
                         || (cmdp->cmdtype == CMDBUILTIN &&
                             builtinloc >= firstchange)) {
                                *pp = cmdp->next;
                                ckfree(cmdp);
                        } else {
                                pp = &cmdp->next;
                        }
                }
        }
        INTON;
}


/*
 * Delete all functions.
 */

#ifdef mkinit
MKINIT void deletefuncs(void);
MKINIT void hash_special_builtins(void);

INIT {
        hash_special_builtins();
}

SHELLPROC {
        deletefuncs();
}
#endif

void
deletefuncs(void)
{
        struct tblentry **tblp;
        struct tblentry **pp;
        struct tblentry *cmdp;

        INTOFF;
        for (tblp = cmdtable ; tblp < &cmdtable[CMDTABLESIZE] ; tblp++) {
                pp = tblp;
                while ((cmdp = *pp) != NULL) {
                        if (cmdp->cmdtype == CMDFUNCTION) {
                                *pp = cmdp->next;
                                freefunc(cmdp->param.func);
                                ckfree(cmdp);
                        } else {
                                pp = &cmdp->next;
                        }
                }
        }
        INTON;
}



/*
 * Locate a command in the command hash table.  If "add" is nonzero,
 * add the command to the table if it is not already present.  The
 * variable "lastcmdentry" is set to point to the address of the link
 * pointing to the entry, so that delete_cmd_entry can delete the
 * entry.
 */

struct tblentry **lastcmdentry;


STATIC struct tblentry *
cmdlookup(const char *name, int add)
{
        int hashval;
        const char *p;
        struct tblentry *cmdp;
        struct tblentry **pp;

        p = name;
        hashval = *p << 4;
        while (*p)
                hashval += *p++;
        hashval &= 0x7FFF;
        pp = &cmdtable[hashval % CMDTABLESIZE];
        for (cmdp = *pp ; cmdp ; cmdp = cmdp->next) {
                if (equal(cmdp->cmdname, name))
                        break;
                pp = &cmdp->next;
        }
        if (add && cmdp == NULL) {
                INTOFF;
                cmdp = *pp = ckmalloc(sizeof (struct tblentry) - ARB
                                        + strlen(name) + 1);
                cmdp->next = NULL;
                cmdp->cmdtype = CMDUNKNOWN;
                cmdp->rehash = 0;
                strcpy(cmdp->cmdname, name);
                INTON;
        }
        lastcmdentry = pp;
        return cmdp;
}

/*
 * Delete the command entry returned on the last lookup.
 */

STATIC void
delete_cmd_entry(void)
{
        struct tblentry *cmdp;

        INTOFF;
        cmdp = *lastcmdentry;
        *lastcmdentry = cmdp->next;
        ckfree(cmdp);
        INTON;
}



#ifdef notdef
void
getcmdentry(char *name, struct cmdentry *entry)
{
        struct tblentry *cmdp = cmdlookup(name, 0);

        if (cmdp) {
                entry->u = cmdp->param;
                entry->cmdtype = cmdp->cmdtype;
        } else {
                entry->cmdtype = CMDUNKNOWN;
                entry->u.index = 0;
        }
}
#endif


/*
 * Add a new command entry, replacing any existing command entry for
 * the same name - except special builtins.
 */

STATIC void
addcmdentry(char *name, struct cmdentry *entry)
{
        struct tblentry *cmdp;

        INTOFF;
        cmdp = cmdlookup(name, 1);
        if (cmdp->cmdtype != CMDSPLBLTIN) {
                if (cmdp->cmdtype == CMDFUNCTION)
                        unreffunc(cmdp->param.func);
                cmdp->cmdtype = entry->cmdtype;
                cmdp->lineno = entry->lineno;
                cmdp->fn_ln1 = entry->lno_frel;
                cmdp->param = entry->u;
        }
        INTON;
}


/*
 * Define a shell function.
 */

void
defun(char *name, union node *func, int lineno)
{
        struct cmdentry entry;

        INTOFF;
        entry.cmdtype = CMDFUNCTION;
        entry.lineno = lineno;
        entry.lno_frel = fnline1;
        entry.u.func = copyfunc(func);
        addcmdentry(name, &entry);
        INTON;
}


/*
 * Delete a function if it exists.
 */

int
unsetfunc(char *name)
{
        struct tblentry *cmdp;

        if ((cmdp = cmdlookup(name, 0)) != NULL &&
            cmdp->cmdtype == CMDFUNCTION) {
                unreffunc(cmdp->param.func);
                delete_cmd_entry();
        }
        return 0;
}

/*
 * Locate and print what a word is...
 * also used for 'command -[v|V]'
 */

int
typecmd(int argc, char **argv)
{
        struct cmdentry entry;
        struct tblentry *cmdp;
        const char * const *pp;
        struct alias *ap;
        int err = 0;
        char *arg;
        int c;
        int V_flag = 0;
        int v_flag = 0;
        int p_flag = 0;

        while ((c = nextopt("vVp")) != 0) {
                switch (c) {
                case 'v': v_flag = 1; break;
                case 'V': V_flag = 1; break;
                case 'p': p_flag = 1; break;
                }
        }

        if (argv[0][0] != 'c' && v_flag | V_flag | p_flag)
                error("usage: %s name...", argv[0]);

        if (v_flag && V_flag)
                error("-v and -V cannot both be specified");

        if (*argptr == NULL)
                error("usage: %s%s name ...", argv[0],
                    argv[0][0] == 'c' ? " [-p] [-v|-V]" : "");

        while ((arg = *argptr++)) {
                if (arg[0] == '\0' && !v_flag) {
                        out1str("'' is an empty string\n");
                        continue;
                }
                if (!v_flag)
                        out1str(arg);
                /* First look at the keywords */
                for (pp = parsekwd; *pp; pp++)
                        if (**pp == *arg && equal(*pp, arg))
                                break;

                if (*pp) {
                        if (v_flag)
                                out1fmt("%s\n", arg);
                        else
                                out1str(" is a shell keyword\n");
                        continue;
                }

                /* Then look at the aliases */
                if ((ap = lookupalias(arg, 1)) != NULL) {
                        int ml = 0;

                        if (!v_flag) {
                                out1str(" is an alias ");
                                if (strchr(ap->val, '\n')) {
                                        out1str("(multiline)...\n");
                                        ml = 1;
                                } else
                                        out1str("for: ");
                        }
                        out1fmt("%s\n", ap->val);
                        if (ml && *argptr != NULL)
                                out1c('\n');
                        continue;
                }

                /* Then check if it is a tracked alias */
                if (!p_flag && (cmdp = cmdlookup(arg, 0)) != NULL) {
                        entry.cmdtype = cmdp->cmdtype;
                        entry.u = cmdp->param;
                } else {
                        cmdp = NULL;
                        /* Finally use brute force */
                        find_command(arg, &entry, DO_ABS,
                             p_flag ? syspath() + 5 : pathval());
                }

                switch (entry.cmdtype) {
                case CMDNORMAL: {
                        if (strchr(arg, '/') == NULL) {
                                const char *path;
                                char *name;
                                int j = entry.u.index;

                                path = p_flag ? syspath() + 5 : pathval();

                                do {
                                        name = padvance(&path, arg, 1);
                                        stunalloc(name);
                                } while (--j >= 0);
                                if (!v_flag)
                                        out1str(" is ");
                                out1fmt("%s\n", name);
                        } else {
                                if (access(arg, X_OK) == 0) {
                                        if (!v_flag)
                                                out1str(" is ");
                                        out1fmt("%s\n", arg);
                                } else {
                                        if (!v_flag)
                                                out1fmt(": %s\n",
                                                    strerror(errno));
                                        else
                                                err = 126;
                                }
                        }
                        break;
                }
                case CMDFUNCTION:
                        if (!v_flag)
                                out1str(" is a shell function\n");
                        else
                                out1fmt("%s\n", arg);
                        break;

                case CMDBUILTIN:
                        if (!v_flag)
                                out1str(" is a shell builtin\n");
                        else
                                out1fmt("%s\n", arg);
                        break;

                case CMDSPLBLTIN:
                        if (!v_flag)
                                out1str(" is a special shell builtin\n");
                        else
                                out1fmt("%s\n", arg);
                        break;

                default:
                        if (!v_flag)
                                out1str(": not found\n");
                        err = 127;
                        break;
                }
        }
        return err;
}