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eval.c

/*    $NetBSD: eval.c,v 1.84 2005/06/23 23:05:29 christos Exp $   */

/*-
 * Copyright (c) 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.
 */

#if 0
#ifndef lint
static char sccsid[] = "@(#)eval.c  8.9 (Berkeley) 6/8/95";
#else
__RCSID("$NetBSD: eval.c,v 1.84 2005/06/23 23:05:29 christos Exp $");
#endif /* not lint */
#endif

#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#ifdef HAVE_SYSCTL_H
# include <sys/sysctl.h>
#endif

/*
 * Evaluate a command.
 */

#include "shell.h"
#include "nodes.h"
#include "syntax.h"
#include "expand.h"
#include "parser.h"
#include "jobs.h"
#include "eval.h"
#include "builtins.h"
#include "options.h"
#include "exec.h"
#include "redir.h"
#include "input.h"
#include "output.h"
#include "trap.h"
#include "var.h"
#include "memalloc.h"
#include "error.h"
#include "show.h"
#include "mystring.h"
#include "main.h"
#ifndef SMALL
# include "myhistedit.h"
#endif
#include "shinstance.h"


/* flags in argument to evaltree */
#define EV_EXIT 01            /* exit after evaluating tree */
#define EV_TESTED 02          /* exit status is checked; ignore -e flag */
#define EV_BACKCMD 04         /* command executing within back quotes */

/*int evalskip;*/             /* set if we are skipping commands */
/*STATIC int skipcount;*/           /* number of levels to skip */
/*MKINIT int loopnest;*/            /* current loop nesting level */
/*int funcnest;*/             /* depth of function calls */


/*char *commandname;*/
/*struct strlist *cmdenviron;*/
/*int exitstatus;*/                 /* exit status of last command */
/*int back_exitstatus;*/            /* exit status of backquoted command */


STATIC void evalloop(shinstance *, union node *, int);
STATIC void evalfor(shinstance *, union node *, int);
STATIC void evalcase(shinstance *, union node *, int);
STATIC void evalsubshell(shinstance *, union node *, int);
STATIC void expredir(shinstance *, union node *);
STATIC void evalpipe(shinstance *, union node *);
STATIC void evalcommand(shinstance *, union node *, int, struct backcmd *);
STATIC void prehash(shinstance *, union node *);


/*
 * Called to reset things after an exception.
 */

#ifdef mkinit
INCLUDE "eval.h"

RESET {
      psh->evalskip = 0;
      psh->loopnest = 0;
      psh->funcnest = 0;
}

SHELLPROC {
      psh->exitstatus = 0;
}
#endif

static int
sh_pipe(shinstance *psh, int fds[2])
{
      int nfd;

      if (shfile_pipe(&psh->fdtab, fds))
            return -1;

      if (fds[0] < 3) {
            nfd = shfile_fcntl(&psh->fdtab, fds[0], F_DUPFD, 3);
            if (nfd != -1) {
                  shfile_close(&psh->fdtab, fds[0]);
                  fds[0] = nfd;
            }
      }

      if (fds[1] < 3) {
            nfd = shfile_fcntl(&psh->fdtab, fds[1], F_DUPFD, 3);
            if (nfd != -1) {
                  shfile_close(&psh->fdtab, fds[1]);
                  fds[1] = nfd;
            }
      }
      return 0;
}


/*
 * The eval commmand.
 */

int
evalcmd(shinstance *psh, int argc, char **argv)
{
      char *p;
      char *concat;
      char **ap;

      if (argc > 1) {
            p = argv[1];
            if (argc > 2) {
                  STARTSTACKSTR(psh, concat);
                  ap = argv + 2;
                  for (;;) {
                        while (*p)
                              STPUTC(psh, *p++, concat);
                        if ((p = *ap++) == NULL)
                              break;
                        STPUTC(psh, ' ', concat);
                  }
                  STPUTC(psh, '\0', concat);
                  p = grabstackstr(psh, concat);
            }
            evalstring(psh, p, EV_TESTED);
      }
      return psh->exitstatus;
}


/*
 * Execute a command or commands contained in a string.
 */

void
evalstring(shinstance *psh, char *s, int flag)
{
      union node *n;
      struct stackmark smark;

      setstackmark(psh, &smark);
      setinputstring(psh, s, 1);

      while ((n = parsecmd(psh, 0)) != NEOF) {
            evaltree(psh, n, flag);
            popstackmark(psh, &smark);
      }
      popfile(psh);
      popstackmark(psh, &smark);
}



/*
 * Evaluate a parse tree.  The value is left in the global variable
 * exitstatus.
 */

void
evaltree(shinstance *psh, union node *n, int flags)
{
      if (n == NULL) {
            TRACE((psh, "evaltree(NULL) called\n"));
            psh->exitstatus = 0;
            goto out;
      }
#ifndef SMALL
      psh->displayhist = 1;   /* show history substitutions done with fc */
#endif
      TRACE((psh, "pid %d, evaltree(%p: %d, %d) called\n",
             sh_getpid(psh), n, n->type, flags));
      switch (n->type) {
      case NSEMI:
            evaltree(psh, n->nbinary.ch1, flags & EV_TESTED);
            if (psh->evalskip)
                  goto out;
            evaltree(psh, n->nbinary.ch2, flags);
            break;
      case NAND:
            evaltree(psh, n->nbinary.ch1, EV_TESTED);
            if (psh->evalskip || psh->exitstatus != 0)
                  goto out;
            evaltree(psh, n->nbinary.ch2, flags);
            break;
      case NOR:
            evaltree(psh, n->nbinary.ch1, EV_TESTED);
            if (psh->evalskip || psh->exitstatus == 0)
                  goto out;
            evaltree(psh, n->nbinary.ch2, flags);
            break;
      case NREDIR:
            expredir(psh, n->nredir.redirect);
            redirect(psh, n->nredir.redirect, REDIR_PUSH);
            evaltree(psh, n->nredir.n, flags);
            popredir(psh);
            break;
      case NSUBSHELL:
            evalsubshell(psh, n, flags);
            break;
      case NBACKGND:
            evalsubshell(psh, n, flags);
            break;
      case NIF: {
            evaltree(psh, n->nif.test, EV_TESTED);
            if (psh->evalskip)
                  goto out;
            if (psh->exitstatus == 0)
                  evaltree(psh, n->nif.ifpart, flags);
            else if (n->nif.elsepart)
                  evaltree(psh, n->nif.elsepart, flags);
            else
                  psh->exitstatus = 0;
            break;
      }
      case NWHILE:
      case NUNTIL:
            evalloop(psh, n, flags);
            break;
      case NFOR:
            evalfor(psh, n, flags);
            break;
      case NCASE:
            evalcase(psh, n, flags);
            break;
      case NDEFUN:
            defun(psh, n->narg.text, n->narg.next);
            psh->exitstatus = 0;
            break;
      case NNOT:
            evaltree(psh, n->nnot.com, EV_TESTED);
            psh->exitstatus = !psh->exitstatus;
            break;
      case NPIPE:
            evalpipe(psh, n);
            break;
      case NCMD:
            evalcommand(psh, n, flags, (struct backcmd *)NULL);
            break;
      default:
            out1fmt(psh, "Node type = %d\n", n->type);
            flushout(&psh->output);
            break;
      }
out:
      if (psh->pendingsigs)
            dotrap(psh);
      if ((flags & EV_EXIT) != 0)
            exitshell(psh, psh->exitstatus);
}


STATIC void
evalloop(shinstance *psh, union node *n, int flags)
{
      int status;

      psh->loopnest++;
      status = 0;
      for (;;) {
            evaltree(psh, n->nbinary.ch1, EV_TESTED);
            if (psh->evalskip) {
skipping:     if (psh->evalskip == SKIPCONT && --psh->skipcount <= 0) {
                        psh->evalskip = 0;
                        continue;
                  }
                  if (psh->evalskip == SKIPBREAK && --psh->skipcount <= 0)
                        psh->evalskip = 0;
                  break;
            }
            if (n->type == NWHILE) {
                  if (psh->exitstatus != 0)
                        break;
            } else {
                  if (psh->exitstatus == 0)
                        break;
            }
            evaltree(psh, n->nbinary.ch2, flags & EV_TESTED);
            status = psh->exitstatus;
            if (psh->evalskip)
                  goto skipping;
      }
      psh->loopnest--;
      psh->exitstatus = status;
}



STATIC void
evalfor(shinstance *psh, union node *n, int flags)
{
      struct arglist arglist;
      union node *argp;
      struct strlist *sp;
      struct stackmark smark;
      int status = 0;

      setstackmark(psh, &smark);
      arglist.lastp = &arglist.list;
      for (argp = n->nfor.args ; argp ; argp = argp->narg.next) {
            expandarg(psh, argp, &arglist, EXP_FULL | EXP_TILDE);
            if (psh->evalskip)
                  goto out;
      }
      *arglist.lastp = NULL;

      psh->loopnest++;
      for (sp = arglist.list ; sp ; sp = sp->next) {
            setvar(psh, n->nfor.var, sp->text, 0);
            evaltree(psh, n->nfor.body, flags & EV_TESTED);
            status = psh->exitstatus;
            if (psh->evalskip) {
                  if (psh->evalskip == SKIPCONT && --psh->skipcount <= 0) {
                        psh->evalskip = 0;
                        continue;
                  }
                  if (psh->evalskip == SKIPBREAK && --psh->skipcount <= 0)
                        psh->evalskip = 0;
                  break;
            }
      }
      psh->loopnest--;
      psh->exitstatus = status;
out:
      popstackmark(psh, &smark);
}



STATIC void
evalcase(shinstance *psh, union node *n, int flags)
{
      union node *cp;
      union node *patp;
      struct arglist arglist;
      struct stackmark smark;
      int status = 0;

      setstackmark(psh, &smark);
      arglist.lastp = &arglist.list;
      expandarg(psh, n->ncase.expr, &arglist, EXP_TILDE);
      for (cp = n->ncase.cases ; cp && psh->evalskip == 0 ; cp = cp->nclist.next) {
            for (patp = cp->nclist.pattern ; patp ; patp = patp->narg.next) {
                  if (casematch(psh, patp, arglist.list->text)) {
                        if (psh->evalskip == 0) {
                              evaltree(psh, cp->nclist.body, flags);
                              status = psh->exitstatus;
                        }
                        goto out;
                  }
            }
      }
out:
      psh->exitstatus = status;
      popstackmark(psh, &smark);
}



/*
 * Kick off a subshell to evaluate a tree.
 */

STATIC void
evalsubshell(shinstance *psh, union node *n, int flags)
{
      struct job *jp;
      int backgnd = (n->type == NBACKGND);

      expredir(psh, n->nredir.redirect);
      INTOFF;
      jp = makejob(psh, n, 1);
      if (forkshell(psh, jp, n, backgnd ? FORK_BG : FORK_FG) == 0) {
            INTON;
            if (backgnd)
                  flags &=~ EV_TESTED;
            redirect(psh, n->nredir.redirect, 0);
            /* never returns */
            evaltree(psh, n->nredir.n, flags | EV_EXIT);
      }
      if (! backgnd)
            psh->exitstatus = waitforjob(psh, jp);
      INTON;
}



/*
 * Compute the names of the files in a redirection list.
 */

STATIC void
expredir(shinstance *psh, union node *n)
{
      union node *redir;

      for (redir = n ; redir ; redir = redir->nfile.next) {
            struct arglist fn;
            fn.lastp = &fn.list;
            switch (redir->type) {
            case NFROMTO:
            case NFROM:
            case NTO:
            case NCLOBBER:
            case NAPPEND:
                  expandarg(psh, redir->nfile.fname, &fn, EXP_TILDE | EXP_REDIR);
                  redir->nfile.expfname = fn.list->text;
                  break;
            case NFROMFD:
            case NTOFD:
                  if (redir->ndup.vname) {
                        expandarg(psh, redir->ndup.vname, &fn, EXP_FULL | EXP_TILDE);
                        fixredir(psh, redir, fn.list->text, 1);
                  }
                  break;
            }
      }
}



/*
 * Evaluate a pipeline.  All the processes in the pipeline are children
 * of the process creating the pipeline.  (This differs from some versions
 * of the shell, which make the last process in a pipeline the parent
 * of all the rest.)
 */

STATIC void
evalpipe(shinstance *psh, union node *n)
{
      struct job *jp;
      struct nodelist *lp;
      int pipelen;
      int prevfd;
      int pip[2];

      TRACE((psh, "evalpipe(0x%lx) called\n", (long)n));
      pipelen = 0;
      for (lp = n->npipe.cmdlist ; lp ; lp = lp->next)
            pipelen++;
      INTOFF;
      jp = makejob(psh, n, pipelen);
      prevfd = -1;
      for (lp = n->npipe.cmdlist ; lp ; lp = lp->next) {
            prehash(psh, lp->n);
            pip[1] = -1;
            if (lp->next) {
                  if (sh_pipe(psh, pip) < 0) {
                        shfile_close(&psh->fdtab, prevfd);
                        error(psh, "Pipe call failed");
                  }
            }
            if (forkshell(psh, jp, lp->n, n->npipe.backgnd ? FORK_BG : FORK_FG) == 0) {
                  INTON;
                  if (prevfd > 0) {
                        shfile_close(&psh->fdtab, 0);
                        copyfd(psh, prevfd, 0);
                        shfile_close(&psh->fdtab, prevfd);
                  }
                  if (pip[1] >= 0) {
                        shfile_close(&psh->fdtab, pip[0]);
                        if (pip[1] != 1) {
                              shfile_close(&psh->fdtab, 1);
                              copyfd(psh, pip[1], 1);
                              shfile_close(&psh->fdtab, pip[1]);
                        }
                  }
                  evaltree(psh, lp->n, EV_EXIT);
            }
            if (prevfd >= 0)
                  shfile_close(&psh->fdtab, prevfd);
            prevfd = pip[0];
            shfile_close(&psh->fdtab, pip[1]);
      }
      if (n->npipe.backgnd == 0) {
            psh->exitstatus = waitforjob(psh, jp);
            TRACE((psh, "evalpipe:  job done exit status %d\n", psh->exitstatus));
      }
      INTON;
}



/*
 * Execute a command inside back quotes.  If it's a builtin command, we
 * want to save its output in a block obtained from malloc.  Otherwise
 * we fork off a subprocess and get the output of the command via a pipe.
 * Should be called with interrupts off.
 */

void
evalbackcmd(shinstance *psh, union node *n, struct backcmd *result)
{
      int pip[2];
      struct job *jp;
      struct stackmark smark;       /* unnecessary */

      setstackmark(psh, &smark);
      result->fd = -1;
      result->buf = NULL;
      result->nleft = 0;
      result->jp = NULL;
      if (n == NULL) {
            goto out;
      }
#ifdef notyet
      /*
       * For now we disable executing builtins in the same
       * context as the shell, because we are not keeping
       * enough state to recover from changes that are
       * supposed only to affect subshells. eg. echo "`cd /`"
       */
      if (n->type == NCMD) {
            psh->exitstatus = opsh->exitstatus;
            evalcommand(psh, n, EV_BACKCMD, result);
      } else
#endif
      {
            INTOFF;
            if (sh_pipe(psh, pip) < 0)
                  error(psh, "Pipe call failed");
            jp = makejob(psh, n, 1);
            if (forkshell(psh, jp, n, FORK_NOJOB) == 0) {
                  FORCEINTON;
                  shfile_close(&psh->fdtab, pip[0]);
                  if (pip[1] != 1) {
                        shfile_close(&psh->fdtab, 1);
                        copyfd(psh, pip[1], 1);
                        shfile_close(&psh->fdtab, pip[1]);
                  }
                  eflag(psh) = 0;
                  evaltree(psh, n, EV_EXIT);
                  /* NOTREACHED */
            }
            shfile_close(&psh->fdtab, pip[1]);
            result->fd = pip[0];
            result->jp = jp;
            INTON;
      }
out:
      popstackmark(psh, &smark);
      TRACE((psh, "evalbackcmd done: fd=%d buf=0x%x nleft=%d jp=0x%x\n",
            result->fd, result->buf, result->nleft, result->jp));
}

static const char *
syspath(shinstance *psh)
{
#ifdef CTL_USER
      static char *sys_path = NULL;
      static int mib[] = {CTL_USER, USER_CS_PATH};
#endif
#ifdef PC_PATH_SEP
      static char def_path[] = "PATH=/usr/bin;/bin;/usr/sbin;/sbin";
#else
      static char def_path[] = "PATH=/usr/bin:/bin:/usr/sbin:/sbin";
#endif
#ifdef CTL_USER
      size_t len;

      if (sys_path == NULL) {
            if (sysctl(mib, 2, 0, &len, 0, 0) != -1 &&
                (sys_path = ckmalloc(len + 5)) != NULL &&
                sysctl(mib, 2, sys_path + 5, &len, 0, 0) != -1) {
                  memcpy(sys_path, "PATH=", 5);
            } else {
                  ckfree(sys_path);
                  /* something to keep things happy */
                  sys_path = def_path;
            }
      }
      return sys_path;
#else
      return def_path;
#endif
}

static int
parse_command_args(shinstance *psh, int argc, char **argv, int *use_syspath)
{
      int sv_argc = argc;
      char *cp, c;

      *use_syspath = 0;

      for (;;) {
            argv++;
            if (--argc == 0)
                  break;
            cp = *argv;
            if (*cp++ != '-')
                  break;
            if (*cp == '-' && cp[1] == 0) {
                  argv++;
                  argc--;
                  break;
            }
            while ((c = *cp++)) {
                  switch (c) {
                  case 'p':
                        *use_syspath = 1;
                        break;
                  default:
                        /* run 'typecmd' for other options */
                        return 0;
                  }
            }
      }
      return sv_argc - argc;
}

/*int vforked = 0;*/

/*
 * Execute a simple command.
 */

STATIC void
evalcommand(shinstance *psh, union node *cmd, int flags, struct backcmd *backcmd)
{
      struct stackmark smark;
      union node *argp;
      struct arglist arglist;
      struct arglist varlist;
      char **argv;
      int argc;
      char **envp;
      int varflag;
      struct strlist *sp;
      int mode;
      int pip[2];
      struct cmdentry cmdentry;
      struct job *jp;
      struct jmploc jmploc;
      struct jmploc *volatile savehandler;
      char *volatile savecmdname;
      volatile struct shparam saveparam;
      struct localvar *volatile savelocalvars;
      volatile int e;
      char *lastarg;
      const char *path = pathval(psh);
      volatile int temp_path;
#if __GNUC__
      /* Avoid longjmp clobbering */
      (void) &argv;
      (void) &argc;
      (void) &lastarg;
      (void) &flags;
#endif

      psh->vforked = 0;
      /* First expand the arguments. */
      TRACE((psh, "evalcommand(0x%lx, %d) called\n", (long)cmd, flags));
      setstackmark(psh, &smark);
      psh->exitstatus = 0;

      arglist.lastp = &arglist.list;
      varflag = 1;
      /* Expand arguments, ignoring the initial 'name=value' ones */
      for (argp = cmd->ncmd.args ; argp ; argp = argp->narg.next) {
            char *p = argp->narg.text;
            if (varflag && is_name(*p)) {
                  do {
                        p++;
                  } while (is_in_name(*p));
                  if (*p == '=')
                        continue;
            }
            expandarg(psh, argp, &arglist, EXP_FULL | EXP_TILDE);
            varflag = 0;
      }
      *arglist.lastp = NULL;

      expredir(psh, cmd->ncmd.redirect);

      /* Now do the initial 'name=value' ones we skipped above */
      varlist.lastp = &varlist.list;
      for (argp = cmd->ncmd.args ; argp ; argp = argp->narg.next) {
            char *p = argp->narg.text;
            if (!is_name(*p))
                  break;
            do
                  p++;
            while (is_in_name(*p));
            if (*p != '=')
                  break;
            expandarg(psh, argp, &varlist, EXP_VARTILDE);
      }
      *varlist.lastp = NULL;

      argc = 0;
      for (sp = arglist.list ; sp ; sp = sp->next)
            argc++;
      argv = stalloc(psh, sizeof (char *) * (argc + 1));

      for (sp = arglist.list ; sp ; sp = sp->next) {
            TRACE((psh, "evalcommand arg: %s\n", sp->text));
            *argv++ = sp->text;
      }
      *argv = NULL;
      lastarg = NULL;
      if (iflag(psh) && psh->funcnest == 0 && argc > 0)
            lastarg = argv[-1];
      argv -= argc;

      /* Print the command if xflag is set. */
      if (xflag(psh)) {
            char sep = 0;
            out2str(psh, ps4val(psh));
            for (sp = varlist.list ; sp ; sp = sp->next) {
                  if (sep != 0)
                        outc(sep, &psh->errout);
                  out2str(psh, sp->text);
                  sep = ' ';
            }
            for (sp = arglist.list ; sp ; sp = sp->next) {
                  if (sep != 0)
                        outc(sep, &psh->errout);
                  out2str(psh, sp->text);
                  sep = ' ';
            }
            outc('\n', &psh->errout);
            flushout(&psh->errout);
      }

      /* Now locate the command. */
      if (argc == 0) {
            cmdentry.cmdtype = CMDSPLBLTIN;
            cmdentry.u.bltin = bltincmd;
      } else {
            static const char PATH[] = "PATH=";
            int cmd_flags = DO_ERR;

            /*
             * Modify the command lookup path, if a PATH= assignment
             * is present
             */
            for (sp = varlist.list; sp; sp = sp->next)
                  if (strncmp(sp->text, PATH, sizeof(PATH) - 1) == 0)
                        path = sp->text + sizeof(PATH) - 1;

            do {
                  int argsused, use_syspath;
                  find_command(psh, argv[0], &cmdentry, cmd_flags, path);
                  if (cmdentry.cmdtype == CMDUNKNOWN) {
                        psh->exitstatus = 127;
                        flushout(&psh->errout);
                        goto out;
                  }

                  /* implement the 'command' builtin here */
                  if (cmdentry.cmdtype != CMDBUILTIN ||
                      cmdentry.u.bltin != bltincmd)
                        break;
                  cmd_flags |= DO_NOFUNC;
                  argsused = parse_command_args(psh, argc, argv, &use_syspath);
                  if (argsused == 0) {
                        /* use 'type' builting to display info */
                        cmdentry.u.bltin = typecmd;
                        break;
                  }
                  argc -= argsused;
                  argv += argsused;
                  if (use_syspath)
                        path = syspath(psh) + 5;
            } while (argc != 0);
            if (cmdentry.cmdtype == CMDSPLBLTIN && cmd_flags & DO_NOFUNC)
                  /* posix mandates that 'command <splbltin>' act as if
                     <splbltin> was a normal builtin */
                  cmdentry.cmdtype = CMDBUILTIN;
      }

      /* Fork off a child process if necessary. */
      if (cmd->ncmd.backgnd
       || (cmdentry.cmdtype == CMDNORMAL && (flags & EV_EXIT) == 0)
       || ((flags & EV_BACKCMD) != 0
          && ((cmdentry.cmdtype != CMDBUILTIN && cmdentry.cmdtype != CMDSPLBLTIN)
             || cmdentry.u.bltin == dotcmd
             || cmdentry.u.bltin == evalcmd))) {
            INTOFF;
            jp = makejob(psh, cmd, 1);
            mode = cmd->ncmd.backgnd;
            if (flags & EV_BACKCMD) {
                  mode = FORK_NOJOB;
                  if (sh_pipe(psh, pip) < 0)
                        error(psh, "Pipe call failed");
            }
#ifdef DO_SHAREDVFORK
            /* It is essential that if DO_SHAREDVFORK is defined that the
             * child's address space is actually shared with the parent as
             * we rely on this.
             */
            if (cmdentry.cmdtype == CMDNORMAL) {
                  pid_t pid;

                  savelocalvars = psh->localvars;
                  psh->localvars = NULL;
                  psh->vforked = 1;
                  switch (pid = vfork()) {
                  case -1:
                        TRACE((psh, "Vfork failed, errno=%d\n", errno));
                        INTON;
                        error(psh, "Cannot vfork");
                        break;
                  case 0:
                        /* Make sure that exceptions only unwind to
                         * after the vfork(2)
                         */
                        if (setjmp(jmploc.loc)) {
                              if (psh->exception == EXSHELLPROC) {
                                    /* We can't progress with the vfork,
                                     * so, set vforked = 2 so the parent
                                     * knows, and _exit();
                                     */
                                    psh->vforked = 2;
                                    sh__exit(psh, 0);
                              } else {
                                    sh__exit(psh, psh->exerrno);
                              }
                        }
                        savehandler = psh->handler;
                        psh->handler = &jmploc;
                        listmklocal(psh, varlist.list, VEXPORT | VNOFUNC);
                        forkchild(psh, jp, cmd, mode, psh->vforked);
                        break;
                  default:
                        psh->handler = savehandler;   /* restore from vfork(2) */
                        poplocalvars(psh);
                        psh->localvars = savelocalvars;
                        if (psh->vforked == 2) {
                              psh->vforked = 0;

                              (void)sh_waitpid(psh, pid, NULL, 0);
                              /* We need to progress in a normal fork fashion */
                              goto normal_fork;
                        }
                        psh->vforked = 0;
                        forkparent(psh, jp, cmd, mode, pid);
                        goto parent;
                  }
            } else {
normal_fork:
#endif
                  if (forkshell(psh, jp, cmd, mode) != 0)
                        goto parent;      /* at end of routine */
                  FORCEINTON;
#ifdef DO_SHAREDVFORK
            }
#endif
            if (flags & EV_BACKCMD) {
                  if (!psh->vforked) {
                        FORCEINTON;
                  }
                  shfile_close(&psh->fdtab, pip[0]);
                  if (pip[1] != 1) {
                        shfile_close(&psh->fdtab, 1);
                        copyfd(psh, pip[1], 1);
                        shfile_close(&psh->fdtab, pip[1]);
                  }
            }
            flags |= EV_EXIT;
      }

      /* This is the child process if a fork occurred. */
      /* Execute the command. */
      switch (cmdentry.cmdtype) {
      case CMDFUNCTION:
#ifdef DEBUG
            trputs(psh, "Shell function:  ");  trargs(psh, argv);
#endif
            redirect(psh, cmd->ncmd.redirect, REDIR_PUSH);
            saveparam = psh->shellparam;
            psh->shellparam.malloc = 0;
            psh->shellparam.reset = 1;
            psh->shellparam.nparam = argc - 1;
            psh->shellparam.p = argv + 1;
            psh->shellparam.optnext = NULL;
            INTOFF;
            savelocalvars = psh->localvars;
            psh->localvars = NULL;
            INTON;
            if (setjmp(jmploc.loc)) {
                  if (psh->exception == EXSHELLPROC) {
                        freeparam((volatile struct shparam *)
                            &saveparam);
                  } else {
                        freeparam(&psh->shellparam);
                        psh->shellparam = saveparam;
                  }
                  poplocalvars(psh);
                  psh->localvars = savelocalvars;
                  psh->handler = savehandler;
                  longjmp(psh->handler->loc, 1);
            }
            savehandler = psh->handler;
            psh->handler = &jmploc;
            listmklocal(psh, varlist.list, 0);
            /* stop shell blowing its stack */
            if (++psh->funcnest > 1000)
                  error(psh, "too many nested function calls");
            evaltree(psh, cmdentry.u.func, flags & EV_TESTED);
            psh->funcnest--;
            INTOFF;
            poplocalvars(psh);
            psh->localvars = savelocalvars;
            freeparam(&psh->shellparam);
            psh->shellparam = saveparam;
            psh->handler = savehandler;
            popredir(psh);
            INTON;
            if (psh->evalskip == SKIPFUNC) {
                  psh->evalskip = 0;
                  psh->skipcount = 0;
            }
            if (flags & EV_EXIT)
                  exitshell(psh, psh->exitstatus);
            break;

      case CMDBUILTIN:
      case CMDSPLBLTIN:
#ifdef DEBUG
            trputs(psh, "builtin command:  ");  trargs(psh, argv);
#endif
            mode = (cmdentry.u.bltin == execcmd) ? 0 : REDIR_PUSH;
            if (flags == EV_BACKCMD) {
                  psh->memout.nleft = 0;
                  psh->memout.nextc = psh->memout.buf;
                  psh->memout.bufsize = 64;
                  mode |= REDIR_BACKQ;
            }
            e = -1;
            savehandler = psh->handler;
            savecmdname = psh->commandname;
            psh->handler = &jmploc;
            if (!setjmp(jmploc.loc)) {
                  /* We need to ensure the command hash table isn't
                   * corruped by temporary PATH assignments.
                   * However we must ensure the 'local' command works!
                   */
                  if (path != pathval(psh) && (cmdentry.u.bltin == hashcmd ||
                      cmdentry.u.bltin == typecmd)) {
                        savelocalvars = psh->localvars;
                        psh->localvars = 0;
                        mklocal(psh, path - 5 /* PATH= */, 0);
                        temp_path = 1;
                  } else
                        temp_path = 0;
                  redirect(psh, cmd->ncmd.redirect, mode);

                  /* exec is a special builtin, but needs this list... */
                  psh->cmdenviron = varlist.list;
                  /* we must check 'readonly' flag for all builtins */
                  listsetvar(psh, varlist.list,
                        cmdentry.cmdtype == CMDSPLBLTIN ? 0 : VNOSET);
                  psh->commandname = argv[0];
                  /* initialize nextopt */
                  psh->argptr = argv + 1;
                  psh->optptr = NULL;
                  /* and getopt */
#if 0 /** @todo fix getop usage! */
#if defined(__FreeBSD__) || defined(__EMX__) || defined(__APPLE__)
                  optreset = 1;
                  optind = 1;
#else
                  optind = 0; /* init */
#endif
#endif

                  psh->exitstatus = cmdentry.u.bltin(psh, argc, argv);
            } else {
                  e = psh->exception;
                  psh->exitstatus = e == EXINT ? SIGINT + 128 :
                              e == EXEXEC ? psh->exerrno : 2;
            }
            psh->handler = savehandler;
            output_flushall(psh);
            psh->out1 = &psh->output;
            psh->out2 = &psh->errout;
            freestdout(psh);
            if (temp_path) {
                  poplocalvars(psh);
                  psh->localvars = savelocalvars;
            }
            psh->cmdenviron = NULL;
            if (e != EXSHELLPROC) {
                  psh->commandname = savecmdname;
                  if (flags & EV_EXIT)
                        exitshell(psh, psh->exitstatus);
            }
            if (e != -1) {
                  if ((e != EXERROR && e != EXEXEC)
                      || cmdentry.cmdtype == CMDSPLBLTIN)
                        exraise(psh, e);
                  FORCEINTON;
            }
            if (cmdentry.u.bltin != execcmd)
                  popredir(psh);
            if (flags == EV_BACKCMD) {
                  backcmd->buf = psh->memout.buf;
                  backcmd->nleft = (int)(psh->memout.nextc - psh->memout.buf);
                  psh->memout.buf = NULL;
            }
            break;

      default:
#ifdef DEBUG
            trputs(psh, "normal command:  ");  trargs(psh, argv);
#endif
            clearredir(psh, psh->vforked);
            redirect(psh, cmd->ncmd.redirect, psh->vforked ? REDIR_VFORK : 0);
            if (!psh->vforked)
                  for (sp = varlist.list ; sp ; sp = sp->next)
                        setvareq(psh, sp->text, VEXPORT|VSTACK);
            envp = environment(psh);
            shellexec(psh, argv, envp, path, cmdentry.u.index, psh->vforked);
            break;
      }
      goto out;

parent:     /* parent process gets here (if we forked) */
      if (mode == FORK_FG) {  /* argument to fork */
            psh->exitstatus = waitforjob(psh, jp);
      } else if (mode == FORK_NOJOB) {
            backcmd->fd = pip[0];
            shfile_close(&psh->fdtab, pip[1]);
            backcmd->jp = jp;
      }
      FORCEINTON;

out:
      if (lastarg)
            /* dsl: I think this is intended to be used to support
             * '_' in 'vi' command mode during line editing...
             * However I implemented that within libedit itself.
             */
            setvar(psh, "_", lastarg, 0);
      popstackmark(psh, &smark);

      if (eflag(psh) && psh->exitstatus && !(flags & EV_TESTED))
            exitshell(psh, psh->exitstatus);
}


/*
 * Search for a command.  This is called before we fork so that the
 * location of the command will be available in the parent as well as
 * the child.  The check for "goodname" is an overly conservative
 * check that the name will not be subject to expansion.
 */

STATIC void
prehash(shinstance *psh, union node *n)
{
      struct cmdentry entry;

      if (n->type == NCMD && n->ncmd.args)
            if (goodname(n->ncmd.args->narg.text))
                  find_command(psh, n->ncmd.args->narg.text, &entry, 0,
                             pathval(psh));
}



/*
 * Builtin commands.  Builtin commands whose functions are closely
 * tied to evaluation are implemented here.
 */

/*
 * No command given.
 */

int
bltincmd(shinstance *psh, int argc, char **argv)
{
      /*
       * Preserve psh->exitstatus of a previous possible redirection
       * as POSIX mandates
       */
      return psh->exitstatus;
}


/*
 * Handle break and continue commands.  Break, continue, and return are
 * all handled by setting the psh->evalskip flag.  The evaluation routines
 * above all check this flag, and if it is set they start skipping
 * commands rather than executing them.  The variable skipcount is
 * the number of loops to break/continue, or the number of function
 * levels to return.  (The latter is always 1.)  It should probably
 * be an error to break out of more loops than exist, but it isn't
 * in the standard shell so we don't make it one here.
 */

int
breakcmd(shinstance *psh, int argc, char **argv)
{
      int n = argc > 1 ? number(psh, argv[1]) : 1;

      if (n > psh->loopnest)
            n = psh->loopnest;
      if (n > 0) {
            psh->evalskip = (**argv == 'c')? SKIPCONT : SKIPBREAK;
            psh->skipcount = n;
      }
      return 0;
}


/*
 * The return command.
 */

int
returncmd(shinstance *psh, int argc, char **argv)
{
      int ret = argc > 1 ? number(psh, argv[1]) : psh->exitstatus;

      if (psh->funcnest) {
            psh->evalskip = SKIPFUNC;
            psh->skipcount = 1;
            return ret;
      }
      else {
            /* Do what ksh does; skip the rest of the file */
            psh->evalskip = SKIPFILE;
            psh->skipcount = 1;
            return ret;
      }
}


int
falsecmd(shinstance *psh, int argc, char **argv)
{
      return 1;
}


int
truecmd(shinstance *psh, int argc, char **argv)
{
      return 0;
}


int
execcmd(shinstance *psh, int argc, char **argv)
{
      if (argc > 1) {
            struct strlist *sp;

            iflag(psh) = 0;         /* exit on error */
            mflag(psh) = 0;
            optschanged(psh);
            for (sp = psh->cmdenviron; sp; sp = sp->next)
                  setvareq(psh, sp->text, VEXPORT|VSTACK);
            shellexec(psh, argv + 1, environment(psh), pathval(psh), 0, 0);
      }
      return 0;
}

static int
conv_time(clock_t ticks, char *seconds, size_t l)
{
      static clock_t tpm = 0;
      clock_t mins;
      size_t i;

      if (!tpm)
            tpm = /*sysconf(_SC_CLK_TCK)*/sh_sysconf_clk_tck() * 60;

      mins = ticks / tpm;
#ifdef _MSC_VER
      {
            char tmp[64];
            sprintf(tmp, "%.4f", (ticks - mins * tpm) * 60.0 / tpm);
            strlcpy(seconds, tmp, l);
      }
#else
      snprintf(seconds, l, "%.4f", (ticks - mins * tpm) * 60.0 / tpm );
#endif

      if (seconds[0] == '6' && seconds[1] == '0') {
            /* 59.99995 got rounded up... */
            mins++;
            strlcpy(seconds, "0.0", l);
            return mins;
      }

      /* suppress trailing zeros */
      i = strlen(seconds) - 1;
      for (; seconds[i] == '0' && seconds[i - 1] != '.'; i--)
            seconds[i] = 0;
      return mins;
}

int
timescmd(shinstance *psh, int argc, char **argv)
{
      shtms tms;
      int u, s, cu, cs;
      char us[8], ss[8], cus[8], css[8];

      nextopt(psh, "");

      sh_times(psh, &tms);

      u = conv_time(tms.tms_utime, us, sizeof(us));
      s = conv_time(tms.tms_stime, ss, sizeof(ss));
      cu = conv_time(tms.tms_cutime, cus, sizeof(cus));
      cs = conv_time(tms.tms_cstime, css, sizeof(css));

      outfmt(psh->out1, "%dm%ss %dm%ss\n%dm%ss %dm%ss\n",
            u, us, s, ss, cu, cus, cs, css);

      return 0;
}

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