/*      $NetBSD: cd.c,v 1.56 2025/08/18 18:58:59 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[] = "@(#)cd.c        8.2 (Berkeley) 5/4/95";
#else
__RCSID("$NetBSD: cd.c,v 1.56 2025/08/18 18:58:59 kre Exp $");
#endif
#endif /* not lint */

#include <sys/types.h>
#include <sys/stat.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>

/*
 * The cd and pwd commands.
 */

#include "shell.h"
#include "var.h"
#include "nodes.h"      /* for jobs.h */
#include "jobs.h"
#include "options.h"
#include "builtins.h"
#include "output.h"
#include "memalloc.h"
#include "error.h"
#include "exec.h"
#include "redir.h"
#include "mystring.h"
#include "show.h"
#include "cd.h"

STATIC int docd(const char *, bool, bool);
STATIC char *getcomponent(void);
STATIC bool updatepwd(const char *);
STATIC void find_curdir(int noerror);
STATIC bool is_curdir(const char *);

char *curdir = NULL;            /* current working directory */
char *prevdir;                  /* previous working directory */
STATIC char *cdcomppath;

int
cdcmd(int argc, char **argv)
{
        const char *dest;
        const char *path, *cp;
        char *p;
        char *d;
        struct stat statb;
        int print = cdprint;    /* set -o cdprint to enable */
        int err = ENOENT;
        int err_set = -1;
        bool eopt = false;
        char opt;

        while ((opt = nextopt("Pe")) != '\0')
                if (opt == 'e')
                        eopt = true;

        /*
         * Try (quite hard) to have 'curdir' defined, nothing has set
         * it on entry to the shell, but we want 'cd fred; cd -' to work.
         */
        getpwd(1);
        dest = *argptr;
        if (dest == NULL) {
                dest = bltinlookup("HOME", 1);
                if (dest == NULL)
                        error("HOME not set");
        } else if (argptr[1]) {
                /* Do 'ksh' style substitution */
                if (!curdir)
                        error("PWD not set");
                p = strstr(curdir, dest);
                if (!p)
                        error("bad substitution (no \"%s\" in \"%s\")",
                            dest, curdir);
                d = stalloc(strlen(curdir) + strlen(argptr[1]) + 1);
                memcpy(d, curdir, p - curdir);
                strcpy(d + (p - curdir), argptr[1]);
                strcat(d, p + strlen(dest));
                dest = d;
                print = 1;
        } else if (dest[0] == '-' && dest[1] == '\0') {
                dest = prevdir ? prevdir : curdir;
                print = 1;
        }
#if 0                           /* POSIX 2024 says this must be an error */
        if (*dest == '\0')
                dest = ".";
#endif

        cp = dest;
        if (*cp == '.' && *++cp == '.')
            cp++;
        if (*cp == 0 || *cp == '/' || (path = bltinlookup("CDPATH", 1)) == NULL)
                path = nullstr;

        cp = dest;
        while ((p = padvance(&path, dest, 0)) != NULL) {
                int dopr = print;
                int x;

                stunalloc(p);
                /* until the next stack write, p remains valid */

                if (stat(p, &statb) < 0) {
                        if (err_set < 0 && errno != ENOENT) {
                                err = errno;
                                cp = stalloc((int)strlen(p) + 1);
                                err_set = 0;
                        }
                        continue;
                }
                if (!S_ISDIR(statb.st_mode)) {
                        if (err_set <= 0) {
                                err = ENOTDIR;
                                cp = stalloc((int)strlen(p) + 1);
                                err_set = 1;
                        }
                        continue;
                }

                if (!print)
                        dopr = strcmp(p, dest);

                if ((x = docd(p, dopr != 0, eopt)) >= 0)
                        return x;

                if (err_set <= 0 && errno != ENOENT) {
                        err = errno;
                        cp = stalloc(strlen(p) + 1);
                        err_set = 1;
                }
        }
        error("Can't cd to \"%s\": %s", cp, strerror(err));
        /* NOTREACHED */
}


/*
 * Actually do the chdir.  In an interactive shell, print the
 * directory name if "print" is nonzero.
 */

STATIC int
docd(const char *dest, bool print, bool eopt)
{
        bool gotpwd;

#if 0           /* no "cd -L" (ever) so all this is just a waste of time ... */
        char *p;
        char *q;
        char *component;
        struct stat statb;
        int first;
        int badstat;

        /*
         *  Check each component of the path. If we find a symlink or
         *  something we can't stat, clear curdir to force a getcwd()
         *  next time we get the value of the current directory.
         */
        badstat = 0;
        cdcomppath = stalloc(strlen(dest) + 1);
        scopy(dest, cdcomppath);
        STARTSTACKSTR(p);
        if (*dest == '/') {
                STPUTC('/', p);
                cdcomppath++;
        }
        first = 1;
        while ((q = getcomponent()) != NULL) {
                if (q[0] == '\0' || (q[0] == '.' && q[1] == '\0'))
                        continue;
                if (! first)
                        STPUTC('/', p);
                first = 0;
                component = q;
                while (*q)
                        STPUTC(*q++, p);
                if (equal(component, ".."))
                        continue;
                STACKSTRNUL(p);
                if (lstat(stackblock(), &statb) < 0) {
                        badstat = 1;
                        break;
                }
        }
#endif

        CTRACE(DBG_CMDS, ("docd(\"%s\", %s, %s) called\n", dest,
            print ? "true" : "false", eopt ? "true" : "false"));


        INTOFF;
        if (chdir(dest) < 0) {
                INTON;          /* If int was pending, this does not return */
                return -1;
        }
        gotpwd = updatepwd(NULL);   /* only do cd -P, no "pretend" -L mode */
        INTON;
        if (!gotpwd && eopt)
                sh_warnx("Unable to determine new working directory");
        else if (print && (iflag || posix))
                out1fmt("%s\n", curdir);
        return gotpwd || !eopt ? 0 : 1;
}


/*
 * Get the next component of the path name pointed to by cdcomppath.
 * This routine overwrites the string pointed to by cdcomppath.
 */

STATIC char *
getcomponent(void)
{
        char *p;
        char *start;

        if ((p = cdcomppath) == NULL)
                return NULL;
        start = cdcomppath;
        while (*p != '/' && *p != '\0')
                p++;
        if (*p == '\0') {
                cdcomppath = NULL;
        } else {
                *p++ = '\0';
                cdcomppath = p;
        }
        return start;
}



/*
 * Update curdir (the name of the current directory) in response to a
 * cd command.  We also call hashcd to let the routines in exec.c know
 * that the current directory has changed.
 */

STATIC bool
updatepwd(const char *dir)
{
        char *new;
        char *p;

        hashcd();                               /* update command hash table */

        /*
         * If our argument is NULL, we don't know the current directory
         * any more because we traversed a symbolic link or something
         * we couldn't stat().   Or we simply don't trust what we had.
         */
        if (dir == NULL || curdir == NULL)  {
                if (prevdir)
                        ckfree(prevdir);
                INTOFF;
                prevdir = curdir;
                curdir = NULL;
                getpwd(1);
                INTON;
                if (curdir) {
                        setvar("OLDPWD", prevdir, VEXPORT);
                        setvar("PWD", curdir, VEXPORT);
                        return true;
                } else
                        unsetvar("PWD", 0);
                return false;
        }

        /* XXX none of the following code is ever executed any more */

        cdcomppath = stalloc(strlen(dir) + 1);
        scopy(dir, cdcomppath);
        STARTSTACKSTR(new);
        if (*dir != '/') {
                p = curdir;
                while (*p)
                        STPUTC(*p++, new);
                if (p[-1] == '/')
                        STUNPUTC(new);
        }
        while ((p = getcomponent()) != NULL) {
                if (equal(p, "..")) {
                        while (new > stackblock() && (STUNPUTC(new), *new) != '/');
                } else if (*p != '\0' && ! equal(p, ".")) {
                        STPUTC('/', new);
                        while (*p)
                                STPUTC(*p++, new);
                }
        }
        if (new == stackblock())
                STPUTC('/', new);
        STACKSTRNUL(new);
        INTOFF;
        if (prevdir)
                ckfree(prevdir);
        prevdir = curdir;
        curdir = savestr(stackblock());
        setvar("OLDPWD", prevdir, VEXPORT);
        setvar("PWD", curdir, VEXPORT);
        INTON;
        return true;
}

/*
 * Test whether we are currently in the direcory given
 * (provided it is given, and is absolute)
 * ie: determine if path is fully qualified pathname of "."
 */
STATIC bool
is_curdir(const char *path)
{
        struct stat stdot, stpath;

        return  path != NULL &&
                *path == '/' &&
                stat(".", &stdot) != -1 &&
                stat(path, &stpath) != -1 &&
                stdot.st_dev == stpath.st_dev &&
                stdot.st_ino == stpath.st_ino;
}

/*
 * Posix says the default should be 'pwd -L' (as below), however
 * the 'cd' command (above) does something much nearer to the
 * posix 'cd -P' (not the posix default of 'cd -L').
 * If 'cd' is changed to support -P/L then the default here
 * needs to be revisited if the historic behaviour is to be kept.
 */

int
pwdcmd(int argc, char **argv)
{
        int i;
        char opt = 'L';

        while ((i = nextopt("LP")) != '\0')
                opt = i;
        if (*argptr)
                error("unexpected argument");

        if (opt == 'L')
                getpwd(0);
        else
                find_curdir(0);

#if 0   /* posix has been changed to forbid this */
        setvar("OLDPWD", prevdir, VEXPORT);
        setvar("PWD", curdir, VEXPORT);
#endif

        if (!is_curdir(curdir)) {
                find_curdir(1);
                if (curdir == NULL)
                        error("Unable to find current directory");
        }

        flushout(out1);         /* make sure buffer is empty */
        clr_err(out1);          /* and forget any earlier errors */
        out1str(curdir);
        out1c('\n');
        flushout(out1);
        if (io_err(out1))
                error("stdout: %s", strerror(errno));

        return 0;
}



void
initpwd(void)
{
        getpwd(1);
        if (curdir)
                setvar("PWD", curdir, VEXPORT);
        else
                sh_warnx("Cannot determine current working directory");
}

#define MAXPWD 256

/*
 * Find out what the current directory is. If we already know the current
 * directory, this routine returns immediately.
 */
void
getpwd(int noerror)
{
        char *pwd;
        static int first = 1;

        if (curdir)
                return;

        if (first) {
                /*
                 * Note that this happens via the call from initpwd()
                 * just above, which is called early from main() during
                 * sh startup, so fetching PWD from the entry environment
                 * (which is what getenv() does) is acceptable.   Here we
                 * could use normal sh var lookup functions instead, as
                 * the arriving environment has already been imported before
                 * we get here, but it makes little difference.
                 *
                 * XXX What would be better perhaps would be to move all of
                 * this into initpwd() instead of here, so we could get rid of
                 * this "first" static - that function is only ever called once.
                 * XXX Some other day.
                 */
                first = 0;
                pwd = getenv("PWD");
                if (is_curdir(pwd)) {
                        curdir = savestr(pwd);
                        return;
                }
        }

        find_curdir(noerror);

        return;
}

STATIC void
find_curdir(int noerror)
{
        int i;
        char *pwd;

        /*
         * Things are a bit complicated here; we could have just used
         * getcwd, but traditionally getcwd is implemented using popen
         * to /bin/pwd. This creates a problem for us, since we cannot
         * keep track of the job if it is being ran behind our backs.
         * XXX That's not actually the problem, a process created and
         * XXX destroyed that we know nothing about is harmless.  The
         * XXX problem is that old popen() implementations would use
         * XXX wait(2) to await completion of the command, and that might
         * XXX collect (and ignore) our children.   As long as we are
         * XXX confident that popen() uses waitpid() (or the equv) there
         * XXX would not be a problem.   But how do we know that?
         * So we re-implement getcwd(), and we suppress interrupts
         * throughout the process. This is not completely safe, since
         * the user can still break out of it by killing the pwd program.
         * We still try to use getcwd for systems that we know have a
         * c implementation of getcwd, that does not open a pipe to
         * /bin/pwd.
         */
#if defined(__NetBSD__) || defined(__SVR4)

        for (i = MAXPWD;; i *= 2) {
                pwd = stalloc(i);
                if (getcwd(pwd, i) != NULL) {
                        curdir = savestr(pwd);
                        stunalloc(pwd);
                        return;
                }
                stunalloc(pwd);
                if (errno == ERANGE)
                        continue;
                if (!noerror)
                        error("getcwd() failed: %s", strerror(errno));
                return;
        }
#else
        {
                char *p;
                int status;
                struct job *jp;
                int pip[2];

                pwd = stalloc(MAXPWD);
                INTOFF;
                if (pipe(pip) < 0)
                        error("Pipe call failed");
                jp = makejob(NULL, 1);
                if (forkshell(jp, NULL, FORK_NOJOB) == 0) {
                        (void) close(pip[0]);
                        movefd(pip[1], 1);
                        (void) execl("/bin/pwd", "pwd", (char *)0);
                        error("Cannot exec /bin/pwd");
                }
                (void) close(pip[1]);
                pip[1] = -1;
                p = pwd;
                while ((i = read(pip[0], p, pwd + MAXPWD - p)) > 0
                     || (i == -1 && errno == EINTR)) {
                        if (i > 0)
                                p += i;
                }
                (void) close(pip[0]);
                pip[0] = -1;
                status = waitforjob(jp);
                if (status != 0)
                        error((char *)0);
                if (i < 0 || p == pwd || p[-1] != '\n') {
                        if (noerror) {
                                INTON;
                                return;
                        }
                        error("pwd command failed");
                }
                p[-1] = '\0';
                INTON;
                curdir = savestr(pwd);
                stunalloc(pwd);
                return;
        }
#endif
}