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exec.c

/*    $NetBSD: exec.c,v 1.37 2003/08/07 09:05:31 agc 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.
 */

#ifdef HAVE_SYS_CDEFS_H
#include <sys/cdefs.h>
#endif
#ifndef lint
#if 0
static char sccsid[] = "@(#)exec.c  8.4 (Berkeley) 6/8/95";
#else
__RCSID("$NetBSD: exec.c,v 1.37 2003/08/07 09:05:31 agc 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"
#ifdef __INNOTEK_LIBC__
#include <InnoTekLIBC/backend.h>
#endif


#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 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, int);
STATIC void execinterp(char **, char **);
STATIC void printentry(struct tblentry *, int);
STATIC void clearcmdentry(int);
STATIC struct tblentry *cmdlookup(const char *, int);
STATIC void delete_cmd_entry(void);
#ifdef PC_EXE_EXTS
STATIC int stat_pc_exec_exts(char *fullname, struct stat *st, int has_ext);
#endif


extern 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;
#ifdef PC_EXE_EXTS
        int has_ext = strlen(argv[0]) - 4;
        has_ext = has_ext > 0
            && argv[0][has_ext] == '.'
            /* use strstr and upper/lower permuated extensions to avoid multiple strcasecmp calls. */
            && strstr("exe;" "Exe;" "EXe;" "EXE;" "ExE;" "eXe;" "eXE;" "exE;"
                      "cmd;" "Cmd;" "CMd;" "CMD;" "CmD;" "cMd;" "cMD;" "cmD;"
                      "com;" "Com;" "COm;" "COM;" "CoM;" "cOm;" "cOM;" "coM;"
                      "bat;" "Bat;" "BAt;" "BAT;" "BaT;" "bAt;" "bAT;" "baT;"
                      "btm;" "Btm;" "BTm;" "BTM;" "BtM;" "bTm;" "bTM;" "btM;",
                      argv[0] + has_ext + 1)
               != NULL;
#else
      const int has_ext = 1;
#endif
      TRACE(("shellexec: argv[0]=%s idx=%d\n", argv[0], idx));
      if (strchr(argv[0], '/') != NULL) {
            cmdname = stalloc(strlen(argv[0]) + 5);
            strcpy(cmdname, argv[0]);
            tryexec(cmdname, argv, envp, vforked, has_ext);
            TRACE(("shellexec: cmdname=%s\n", cmdname));
            stunalloc(cmdname);
            e = errno;
      } else {
            e = ENOENT;
            while ((cmdname = padvance(&path, argv[0])) != NULL) {
                  if (--idx < 0 && pathopt == NULL) {
                        tryexec(cmdname, argv, envp, vforked, has_ext);
                        if (errno != ENOENT && errno != ENOTDIR)
                              e = errno;
                  }
                  stunalloc(cmdname);
            }
      }

      /* Map to POSIX errors */
      switch (e) {
      case EACCES:
            exerrno = 126;
            break;
      case ENOENT:
            exerrno = 127;
            break;
      default:
            exerrno = 2;
            break;
      }
      TRACE(("shellexec failed for '%s', errno %d, vforked %d, suppressint %d\n",
            argv[0], e, vforked, suppressint ));
      exerror(EXEXEC, "%s: %s", argv[0], errmsg(e, E_EXEC));
      /* NOTREACHED */
}


STATIC void
tryexec(char *cmd, char **argv, char **envp, int vforked, int has_ext)
{
      int e;
#ifdef EXEC_HASH_BANG_SCRIPT
      char *p;
#endif
#ifdef PC_EXE_EXTS
        /* exploit the effect of stat_pc_exec_exts which adds the
         * correct extentions to the file.
         */
        struct stat st;
        if (!has_ext)
            stat_pc_exec_exts(cmd, &st, 0);
#endif
#if defined __INNOTEK_LIBC__ && defined EXEC_HASH_BANG_SCRIPT
      __libc_Back_gfProcessHandleHashBangScripts = 0;
#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);
            }
            initshellproc();
            setinputfile(cmd, 0);
            commandname = arg0 = savestr(argv[0]);
#ifdef EXEC_HASH_BANG_SCRIPT
            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;
}


#ifdef EXEC_HASH_BANG_SCRIPT
/*
 * 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")) {
                        TRACE(("hash bang self\n"));
                        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++);
      TRACE(("hash bang '%s'\n", new[0]));
      shellexec(new, envp, pathval(), 0, 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)
{
      const char *p;
      char *q;
#ifdef PC_SLASHES
      char *s;
#endif
      const char *start;
      int len;

      if (*path == NULL)
            return NULL;
      start = *path;
#ifdef PC_PATH_SEP
      for (p = start ; *p && *p != ';' && *p != '%' ; p++);
#else
      for (p = start ; *p && *p != ':' && *p != '%' ; p++);
#endif
      len = p - start + strlen(name) + 2; /* "2" is for '/' and '\0' */
#ifdef PC_EXE_EXTS
        len += 4; /* "4" is for .exe/.com/.cmd/.bat/.btm */
#endif
      while (stackblocksize() < len)
            growstackblock();
#ifdef PC_SLASHES
      s =
#endif
      q = stackblock();
      if (p != start) {
            memcpy(q, start, p - start);
            q += p - start;
            *q++ = '/';
      }
      strcpy(q, name);
#ifdef PC_SLASHES
      while ((s = strchr(s, '\\')) != NULL)
            *s++ = '/';
#endif
      pathopt = NULL;
      if (*p == '%') {
            pathopt = ++p;
#ifdef PC_PATH_SEP
            while (*p && *p != ';')  p++;
#else
            while (*p && *p != ':')  p++;
#endif
      }
#ifdef PC_PATH_SEP
      if (*p == ';')
#else
      if (*p == ':')
#endif
            *path = p + 1;
      else
            *path = NULL;
      return stalloc(len);
}


#ifdef PC_EXE_EXTS
STATIC int stat_pc_exec_exts(char *fullname, struct stat *st, int has_ext)
{
    /* skip the SYSV crap */
    if (stat(fullname, st) >= 0)
        return 0;
    if (!has_ext && errno == ENOENT)
    {
        char *psz = strchr(fullname, '\0');
        memcpy(psz, ".exe", 5);
        if (stat(fullname, st) >= 0)
            return 0;
        if (errno != ENOENT && errno != ENOTDIR)
            return -1;

        memcpy(psz, ".cmd", 5);
        if (stat(fullname, st) >= 0)
            return 0;
        if (errno != ENOENT && errno != ENOTDIR)
            return -1;

        memcpy(psz, ".bat", 5);
        if (stat(fullname, st) >= 0)
            return 0;
        if (errno != ENOENT && errno != ENOTDIR)
            return -1;

        memcpy(psz, ".com", 5);
        if (stat(fullname, st) >= 0)
            return 0;
        if (errno != ENOENT && errno != ENOTDIR)
            return -1;

        memcpy(psz, ".btm", 5);
        if (stat(fullname, st) >= 0)
            return 0;
        *psz = '\0';
    }
    return -1;
}
#endif /* PC_EXE_EXTS */



/*** Command hashing code ***/


int
hashcmd(int argc, char **argv)
{
      struct tblentry **pp;
      struct tblentry *cmdp;
      int c;
      int verbose;
      struct cmdentry entry;
      char *name;

      verbose = 0;
      while ((c = nextopt("rv")) != '\0') {
            if (c == 'r') {
                  clearcmdentry(0);
            } else if (c == 'v') {
                  verbose++;
            }
      }
      if (*argptr == NULL) {
            for (pp = cmdtable ; pp < &cmdtable[CMDTABLESIZE] ; pp++) {
                  for (cmdp = *pp ; cmdp ; cmdp = cmdp->next) {
                        if (verbose || cmdp->cmdtype == CMDNORMAL)
                              printentry(cmdp, verbose);
                  }
            }
            return 0;
      }
      while ((name = *argptr) != NULL) {
            if ((cmdp = cmdlookup(name, 0)) != NULL
             && (cmdp->cmdtype == CMDNORMAL
                 || (cmdp->cmdtype == CMDBUILTIN && builtinloc >= 0)))
                  delete_cmd_entry();
            find_command(name, &entry, DO_ERR, pathval());
            if (verbose) {
                  if (entry.cmdtype != CMDUNKNOWN) {  /* if no error msg */
                        cmdp = cmdlookup(name, 0);
                        printentry(cmdp, verbose);
                  }
                  output_flushall();
            }
            argptr++;
      }
      return 0;
}


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);
                  stunalloc(name);
            } while (--idx >= 0);
            out1str(name);
            break;
      case CMDSPLBLTIN:
            out1fmt("special builtin %s", cmdp->cmdname);
            break;
      case CMDBUILTIN:
            out1fmt("builtin %s", cmdp->cmdname);
            break;
      case CMDFUNCTION:
            out1fmt("function %s", cmdp->cmdname);
            if (verbose) {
                  struct procstat ps;
                  INTOFF;
                  commandtext(&ps, 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 **);

#ifdef PC_EXE_EXTS
        int has_ext = strlen(name) - 4;
        has_ext = has_ext > 0
            && name[has_ext] == '.'
            /* use strstr and upper/lower permuated extensions to avoid multiple strcasecmp calls. */
            && strstr("exe;" "Exe;" "EXe;" "EXE;" "ExE;" "eXe;" "eXE;" "exE;"
                      "cmd;" "Cmd;" "CMd;" "CMD;" "CmD;" "cMd;" "cMD;" "cmD;"
                      "com;" "Com;" "COm;" "COM;" "CoM;" "cOm;" "cOM;" "coM;"
                      "bat;" "Bat;" "BAt;" "BAT;" "BaT;" "bAt;" "bAT;" "baT;"
                      "btm;" "Btm;" "BTm;" "BTM;" "BtM;" "bTm;" "bTM;" "btM;",
                      name + has_ext + 1)
               != NULL;
#endif

      /* 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) {
            do {
                  switch (cmdp->cmdtype) {
                  case CMDNORMAL:
                        if (act & DO_ALTPATH) {
                              cmdp = NULL;
                              continue;
                        }
                        break;
                  case CMDFUNCTION:
                        if (act & DO_NOFUNC) {
                              cmdp = NULL;
                              continue;
                        }
                        break;
                  case CMDBUILTIN:
                        if ((act & DO_ALTBLTIN) || builtinloc >= 0) {
                              cmdp = NULL;
                              continue;
                        }
                        break;
                  }
                  /* if not invalidated by cd, we're done */
                  if (cmdp->rehash == 0)
                        goto success;
            } while (0);
      }

      /* 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)) != 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;
                  TRACE(("searchexec \"%s\": no change\n", name));
                  goto success;
            }
#ifdef PC_EXE_EXTS
            while (stat_pc_exec_exts(fullname, &statb, has_ext) < 0) {
#else
            while (stat(fullname, &statb) < 0) {
#endif
#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 */
                  if (act & DO_NOFUNC)
                        goto loop;
                  stalloc(strlen(fullname) + 1);
                  readcmdfile(fullname);
                  if ((cmdp = cmdlookup(name, 0)) == NULL ||
                      cmdp->cmdtype != CMDFUNCTION)
                        error("%s not defined in %s", name, fullname);
                  stunalloc(fullname);
                  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
            TRACE(("searchexec \"%s\" returns \"%s\"\n", name, fullname));
            INTOFF;
            if (act & DO_ALTPATH) {
                  stalloc(strlen(fullname) + 1);
                  cmdp = &loc_cmd;
            } else
                  cmdp = cmdlookup(name, 1);
            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;
      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:
      cmdp->rehash = 0;
      entry->cmdtype = cmdp->cmdtype;
      entry->u = cmdp->param;
}



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

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

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

int
(*find_splbltin(name))(int, char **)
      char *name;
{
      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 *newval)
{
      const char *old, *new;
      int idx;
      int firstchange;
      int bltin;

      old = pathval();
      new = newval;
      firstchange = 9999;     /* assume no change */
      idx = 0;
      bltin = -1;
      for (;;) {
            if (*old != *new) {
                  firstchange = idx;
#ifdef PC_PATH_SEP
                  if ((*old == '\0' && *new == ';')
                   || (*old == ';' && *new == '\0'))
#else
                  if ((*old == '\0' && *new == ':')
                   || (*old == ':' && *new == '\0'))
#endif
                        firstchange++;
                  old = new;  /* ignore subsequent differences */
            }
            if (*new == '\0')
                  break;
            if (*new == '%' && bltin < 0 && prefix("builtin", new + 1))
                  bltin = idx;
#ifdef PC_PATH_SEP
            if (*new == ';') {
#else
            if (*new == ':') {
#endif
                  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) {
                  freefunc(cmdp->param.func);
            }
            cmdp->cmdtype = entry->cmdtype;
            cmdp->param = entry->u;
      }
      INTON;
}


/*
 * Define a shell function.
 */

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

      INTOFF;
      entry.cmdtype = CMDFUNCTION;
      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) {
            freefunc(cmdp->param.func);
            delete_cmd_entry();
            return (0);
      }
      return (1);
}

/*
 * 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;
      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 (p_flag && (v_flag || V_flag))
            error("cannot specify -p with -v or -V");

      while ((arg = *argptr++)) {
            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)
                        err = 1;
                  else
                        out1str(" is a shell keyword\n");
                  continue;
            }

            /* Then look at the aliases */
            if ((ap = lookupalias(arg, 1)) != NULL) {
                  if (!v_flag)
                        out1fmt(" is an alias for \n");
                  out1fmt("%s\n", ap->val);
                  continue;
            }

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

            switch (entry.cmdtype) {
            case CMDNORMAL: {
                  if (strchr(arg, '/') == NULL) {
                        const char *path = pathval();
                        char *name;
                        int j = entry.u.index;
                        do {
                              name = padvance(&path, arg);
                              stunalloc(name);
                        } while (--j >= 0);
                        if (!v_flag)
                              out1fmt(" is%s ",
                                  cmdp ? " a tracked alias for" : "");
                        out1fmt("%s\n", name);
                  } else {
                        if (access(arg, X_OK) == 0) {
                              if (!v_flag)
                                    out1fmt(" 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;
}

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