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[apple/shell_cmds.git] / sh / eval.c
diff --git a/sh/eval.c b/sh/eval.c
new file mode 100644 (file)
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--- /dev/null
+++ b/sh/eval.c
@@ -0,0 +1,1382 @@
+/*-
+ * 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.
+ * 4. 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.
+ */
+
+#ifndef lint
+#if 0
+static char sccsid[] = "@(#)eval.c     8.9 (Berkeley) 6/8/95";
+#endif
+#endif /* not lint */
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <paths.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/resource.h>
+#include <sys/wait.h> /* For WIFSIGNALED(status) */
+#include <errno.h>
+
+/*
+ * 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"
+#ifndef NO_HISTORY
+#include "myhistedit.h"
+#endif
+
+
+int evalskip;                  /* set if we are skipping commands */
+int skipcount;                 /* number of levels to skip */
+static int loopnest;           /* current loop nesting level */
+int funcnest;                  /* depth of function calls */
+static int builtin_flags;      /* evalcommand flags for builtins */
+
+
+char *commandname;
+struct strlist *cmdenviron;
+int exitstatus;                        /* exit status of last command */
+int oexitstatus;               /* saved exit status */
+
+
+static void evalloop(union node *, int);
+static void evalfor(union node *, int);
+static union node *evalcase(union node *);
+static void evalsubshell(union node *, int);
+static void evalredir(union node *, int);
+static void exphere(union node *, struct arglist *);
+static void expredir(union node *);
+static void evalpipe(union node *);
+static int is_valid_fast_cmdsubst(union node *n);
+static void evalcommand(union node *, int, struct backcmd *);
+static void prehash(union node *);
+
+
+/*
+ * Called to reset things after an exception.
+ */
+
+void
+reseteval(void)
+{
+       evalskip = 0;
+       loopnest = 0;
+}
+
+
+/*
+ * The eval command.
+ */
+
+int
+evalcmd(int argc, char **argv)
+{
+        char *p;
+        char *concat;
+        char **ap;
+
+        if (argc > 1) {
+                p = argv[1];
+                if (argc > 2) {
+                        STARTSTACKSTR(concat);
+                        ap = argv + 2;
+                        for (;;) {
+                                STPUTS(p, concat);
+                                if ((p = *ap++) == NULL)
+                                        break;
+                                STPUTC(' ', concat);
+                        }
+                        STPUTC('\0', concat);
+                        p = grabstackstr(concat);
+                }
+                evalstring(p, builtin_flags);
+        } else
+                exitstatus = 0;
+        return exitstatus;
+}
+
+
+/*
+ * Execute a command or commands contained in a string.
+ */
+
+void
+evalstring(const char *s, int flags)
+{
+       union node *n;
+       struct stackmark smark;
+       int flags_exit;
+       int any;
+
+       flags_exit = flags & EV_EXIT;
+       flags &= ~EV_EXIT;
+       any = 0;
+       setstackmark(&smark);
+       setinputstring(s, 1);
+       while ((n = parsecmd(0)) != NEOF) {
+               if (n != NULL && !nflag) {
+                       if (flags_exit && preadateof())
+                               evaltree(n, flags | EV_EXIT);
+                       else
+                               evaltree(n, flags);
+                       any = 1;
+                       if (evalskip)
+                               break;
+               }
+               popstackmark(&smark);
+               setstackmark(&smark);
+       }
+       popfile();
+       popstackmark(&smark);
+       if (!any)
+               exitstatus = 0;
+       if (flags_exit)
+               exraise(EXEXIT);
+}
+
+
+/*
+ * Evaluate a parse tree.  The value is left in the global variable
+ * exitstatus.
+ */
+
+void
+evaltree(union node *n, int flags)
+{
+       int do_etest;
+       union node *next;
+       struct stackmark smark;
+
+       setstackmark(&smark);
+       do_etest = 0;
+       if (n == NULL) {
+               TRACE(("evaltree(NULL) called\n"));
+               exitstatus = 0;
+               goto out;
+       }
+       do {
+               next = NULL;
+#ifndef NO_HISTORY
+               displayhist = 1;        /* show history substitutions done with fc */
+#endif
+               TRACE(("evaltree(%p: %d) called\n", (void *)n, n->type));
+               switch (n->type) {
+               case NSEMI:
+                       evaltree(n->nbinary.ch1, flags & ~EV_EXIT);
+                       if (evalskip)
+                               goto out;
+                       next = n->nbinary.ch2;
+                       break;
+               case NAND:
+                       evaltree(n->nbinary.ch1, EV_TESTED);
+                       if (evalskip || exitstatus != 0) {
+                               goto out;
+                       }
+                       next = n->nbinary.ch2;
+                       break;
+               case NOR:
+                       evaltree(n->nbinary.ch1, EV_TESTED);
+                       if (evalskip || exitstatus == 0)
+                               goto out;
+                       next = n->nbinary.ch2;
+                       break;
+               case NREDIR:
+                       evalredir(n, flags);
+                       break;
+               case NSUBSHELL:
+                       evalsubshell(n, flags);
+                       do_etest = !(flags & EV_TESTED);
+                       break;
+               case NBACKGND:
+                       evalsubshell(n, flags);
+                       break;
+               case NIF: {
+                       evaltree(n->nif.test, EV_TESTED);
+                       if (evalskip)
+                               goto out;
+                       if (exitstatus == 0)
+                               next = n->nif.ifpart;
+                       else if (n->nif.elsepart)
+                               next = n->nif.elsepart;
+                       else
+                               exitstatus = 0;
+                       break;
+               }
+               case NWHILE:
+               case NUNTIL:
+                       evalloop(n, flags & ~EV_EXIT);
+                       break;
+               case NFOR:
+                       evalfor(n, flags & ~EV_EXIT);
+                       break;
+               case NCASE:
+                       next = evalcase(n);
+                       break;
+               case NCLIST:
+                       next = n->nclist.body;
+                       break;
+               case NCLISTFALLTHRU:
+                       if (n->nclist.body) {
+                               evaltree(n->nclist.body, flags & ~EV_EXIT);
+                               if (evalskip)
+                                       goto out;
+                       }
+                       next = n->nclist.next;
+                       break;
+               case NDEFUN:
+                       defun(n->narg.text, n->narg.next);
+                       exitstatus = 0;
+                       break;
+               case NNOT:
+                       evaltree(n->nnot.com, EV_TESTED);
+                       if (evalskip)
+                               goto out;
+                       exitstatus = !exitstatus;
+                       break;
+
+               case NPIPE:
+                       evalpipe(n);
+                       do_etest = !(flags & EV_TESTED);
+                       break;
+               case NCMD:
+                       evalcommand(n, flags, (struct backcmd *)NULL);
+                       do_etest = !(flags & EV_TESTED);
+                       break;
+               default:
+                       out1fmt("Node type = %d\n", n->type);
+                       flushout(&output);
+                       break;
+               }
+               n = next;
+               popstackmark(&smark);
+               setstackmark(&smark);
+       } while (n != NULL);
+out:
+       popstackmark(&smark);
+       if (pendingsig)
+               dotrap();
+       if (eflag && exitstatus != 0 && do_etest)
+               exitshell(exitstatus);
+       if (flags & EV_EXIT)
+               exraise(EXEXIT);
+}
+
+
+static void
+evalloop(union node *n, int flags)
+{
+       int status;
+
+       loopnest++;
+       status = 0;
+       for (;;) {
+               if (!evalskip)
+                       evaltree(n->nbinary.ch1, EV_TESTED);
+               if (evalskip) {
+                       if (evalskip == SKIPCONT && --skipcount <= 0) {
+                               evalskip = 0;
+                               continue;
+                       }
+                       if (evalskip == SKIPBREAK && --skipcount <= 0)
+                               evalskip = 0;
+                       if (evalskip == SKIPRETURN)
+                               status = exitstatus;
+                       break;
+               }
+               if (n->type == NWHILE) {
+                       if (exitstatus != 0)
+                               break;
+               } else {
+                       if (exitstatus == 0)
+                               break;
+               }
+               evaltree(n->nbinary.ch2, flags);
+               status = exitstatus;
+       }
+       loopnest--;
+       exitstatus = status;
+}
+
+
+
+static void
+evalfor(union node *n, int flags)
+{
+       struct arglist arglist;
+       union node *argp;
+       struct strlist *sp;
+       int status;
+
+       arglist.lastp = &arglist.list;
+       for (argp = n->nfor.args ; argp ; argp = argp->narg.next) {
+               oexitstatus = exitstatus;
+               expandarg(argp, &arglist, EXP_FULL | EXP_TILDE);
+       }
+       *arglist.lastp = NULL;
+
+       loopnest++;
+       status = 0;
+       for (sp = arglist.list ; sp ; sp = sp->next) {
+               setvar(n->nfor.var, sp->text, 0);
+               evaltree(n->nfor.body, flags);
+               status = exitstatus;
+               if (evalskip) {
+                       if (evalskip == SKIPCONT && --skipcount <= 0) {
+                               evalskip = 0;
+                               continue;
+                       }
+                       if (evalskip == SKIPBREAK && --skipcount <= 0)
+                               evalskip = 0;
+                       break;
+               }
+       }
+       loopnest--;
+       exitstatus = status;
+}
+
+
+/*
+ * Evaluate a case statement, returning the selected tree.
+ *
+ * The exit status needs care to get right.
+ */
+
+static union node *
+evalcase(union node *n)
+{
+       union node *cp;
+       union node *patp;
+       struct arglist arglist;
+
+       arglist.lastp = &arglist.list;
+       oexitstatus = exitstatus;
+       expandarg(n->ncase.expr, &arglist, EXP_TILDE);
+       for (cp = n->ncase.cases ; cp ; cp = cp->nclist.next) {
+               for (patp = cp->nclist.pattern ; patp ; patp = patp->narg.next) {
+                       if (casematch(patp, arglist.list->text)) {
+                               while (cp->nclist.next &&
+                                   cp->type == NCLISTFALLTHRU &&
+                                   cp->nclist.body == NULL)
+                                       cp = cp->nclist.next;
+                               if (cp->nclist.next &&
+                                   cp->type == NCLISTFALLTHRU)
+                                       return (cp);
+                               if (cp->nclist.body == NULL)
+                                       exitstatus = 0;
+                               return (cp->nclist.body);
+                       }
+               }
+       }
+       exitstatus = 0;
+       return (NULL);
+}
+
+
+
+/*
+ * Kick off a subshell to evaluate a tree.
+ */
+
+static void
+evalsubshell(union node *n, int flags)
+{
+       struct job *jp;
+       int backgnd = (n->type == NBACKGND);
+
+       oexitstatus = exitstatus;
+       expredir(n->nredir.redirect);
+       if ((!backgnd && flags & EV_EXIT && !have_traps()) ||
+                       forkshell(jp = makejob(n, 1), n, backgnd) == 0) {
+               if (backgnd)
+                       flags &=~ EV_TESTED;
+               redirect(n->nredir.redirect, 0);
+               evaltree(n->nredir.n, flags | EV_EXIT); /* never returns */
+       } else if (! backgnd) {
+               INTOFF;
+               exitstatus = waitforjob(jp, (int *)NULL);
+               INTON;
+       } else
+               exitstatus = 0;
+}
+
+
+/*
+ * Evaluate a redirected compound command.
+ */
+
+static void
+evalredir(union node *n, int flags)
+{
+       struct jmploc jmploc;
+       struct jmploc *savehandler;
+       volatile int in_redirect = 1;
+
+       oexitstatus = exitstatus;
+       expredir(n->nredir.redirect);
+       savehandler = handler;
+       if (setjmp(jmploc.loc)) {
+               int e;
+
+               handler = savehandler;
+               e = exception;
+               popredir();
+               if (e == EXERROR || e == EXEXEC) {
+                       if (in_redirect) {
+                               exitstatus = 2;
+                               return;
+                       }
+               }
+               longjmp(handler->loc, 1);
+       } else {
+               INTOFF;
+               handler = &jmploc;
+               redirect(n->nredir.redirect, REDIR_PUSH);
+               in_redirect = 0;
+               INTON;
+               evaltree(n->nredir.n, flags);
+       }
+       INTOFF;
+       handler = savehandler;
+       popredir();
+       INTON;
+}
+
+
+static void
+exphere(union node *redir, struct arglist *fn)
+{
+       struct jmploc jmploc;
+       struct jmploc *savehandler;
+       struct localvar *savelocalvars;
+       int need_longjmp = 0;
+
+       redir->nhere.expdoc = "";
+       savelocalvars = localvars;
+       localvars = NULL;
+       forcelocal++;
+       savehandler = handler;
+       if (setjmp(jmploc.loc))
+               need_longjmp = exception != EXERROR && exception != EXEXEC;
+       else {
+               handler = &jmploc;
+               expandarg(redir->nhere.doc, fn, 0);
+               redir->nhere.expdoc = fn->list->text;
+               INTOFF;
+       }
+       handler = savehandler;
+       forcelocal--;
+       poplocalvars();
+       localvars = savelocalvars;
+       if (need_longjmp)
+               longjmp(handler->loc, 1);
+       INTON;
+}
+
+
+/*
+ * Compute the names of the files in a redirection list.
+ */
+
+static void
+expredir(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 NFROM:
+               case NTO:
+               case NFROMTO:
+               case NAPPEND:
+               case NCLOBBER:
+                       expandarg(redir->nfile.fname, &fn, EXP_TILDE);
+                       redir->nfile.expfname = fn.list->text;
+                       break;
+               case NFROMFD:
+               case NTOFD:
+                       if (redir->ndup.vname) {
+                               expandarg(redir->ndup.vname, &fn, EXP_TILDE);
+                               fixredir(redir, fn.list->text, 1);
+                       }
+                       break;
+               case NXHERE:
+                       exphere(redir, &fn);
+                       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(union node *n)
+{
+       struct job *jp;
+       struct nodelist *lp;
+       int pipelen;
+       int prevfd;
+       int pip[2];
+
+       TRACE(("evalpipe(%p) called\n", (void *)n));
+       pipelen = 0;
+       for (lp = n->npipe.cmdlist ; lp ; lp = lp->next)
+               pipelen++;
+       INTOFF;
+       jp = makejob(n, pipelen);
+       prevfd = -1;
+       for (lp = n->npipe.cmdlist ; lp ; lp = lp->next) {
+               prehash(lp->n);
+               pip[1] = -1;
+               if (lp->next) {
+                       if (pipe(pip) < 0) {
+                               if (prevfd >= 0)
+                                       close(prevfd);
+                               error("Pipe call failed: %s", strerror(errno));
+                       }
+               }
+               if (forkshell(jp, lp->n, n->npipe.backgnd) == 0) {
+                       INTON;
+                       if (prevfd > 0) {
+                               dup2(prevfd, 0);
+                               close(prevfd);
+                       }
+                       if (pip[1] >= 0) {
+                               if (!(prevfd >= 0 && pip[0] == 0))
+                                       close(pip[0]);
+                               if (pip[1] != 1) {
+                                       dup2(pip[1], 1);
+                                       close(pip[1]);
+                               }
+                       }
+                       evaltree(lp->n, EV_EXIT);
+               }
+               if (prevfd >= 0)
+                       close(prevfd);
+               prevfd = pip[0];
+               if (pip[1] != -1)
+                       close(pip[1]);
+       }
+       INTON;
+       if (n->npipe.backgnd == 0) {
+               INTOFF;
+               exitstatus = waitforjob(jp, (int *)NULL);
+               TRACE(("evalpipe:  job done exit status %d\n", exitstatus));
+               INTON;
+       } else
+               exitstatus = 0;
+}
+
+
+
+static int
+is_valid_fast_cmdsubst(union node *n)
+{
+
+       return (n->type == NCMD);
+}
+
+/*
+ * 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(union node *n, struct backcmd *result)
+{
+       int pip[2];
+       struct job *jp;
+       struct stackmark smark;
+       struct jmploc jmploc;
+       struct jmploc *savehandler;
+       struct localvar *savelocalvars;
+
+       result->fd = -1;
+       result->buf = NULL;
+       result->nleft = 0;
+       result->jp = NULL;
+       if (n == NULL) {
+               exitstatus = 0;
+               return;
+       }
+       setstackmark(&smark);
+       exitstatus = oexitstatus;
+       if (is_valid_fast_cmdsubst(n)) {
+               savelocalvars = localvars;
+               localvars = NULL;
+               forcelocal++;
+               savehandler = handler;
+               if (setjmp(jmploc.loc)) {
+                       if (exception == EXERROR || exception == EXEXEC)
+                               exitstatus = 2;
+                       else if (exception != 0) {
+                               handler = savehandler;
+                               forcelocal--;
+                               poplocalvars();
+                               localvars = savelocalvars;
+                               longjmp(handler->loc, 1);
+                       }
+               } else {
+                       handler = &jmploc;
+                       evalcommand(n, EV_BACKCMD, result);
+               }
+               handler = savehandler;
+               forcelocal--;
+               poplocalvars();
+               localvars = savelocalvars;
+       } else {
+               if (pipe(pip) < 0)
+                       error("Pipe call failed: %s", strerror(errno));
+               jp = makejob(n, 1);
+               if (forkshell(jp, n, FORK_NOJOB) == 0) {
+                       FORCEINTON;
+                       close(pip[0]);
+                       if (pip[1] != 1) {
+                               dup2(pip[1], 1);
+                               close(pip[1]);
+                       }
+                       evaltree(n, EV_EXIT);
+               }
+               close(pip[1]);
+               result->fd = pip[0];
+               result->jp = jp;
+       }
+       popstackmark(&smark);
+       TRACE(("evalbackcmd done: fd=%d buf=%p nleft=%d jp=%p\n",
+               result->fd, result->buf, result->nleft, result->jp));
+}
+
+static int
+mustexpandto(const char *argtext, const char *mask)
+{
+       for (;;) {
+               if (*argtext == CTLQUOTEMARK || *argtext == CTLQUOTEEND) {
+                       argtext++;
+                       continue;
+               }
+               if (*argtext == CTLESC)
+                       argtext++;
+               else if (BASESYNTAX[(int)*argtext] == CCTL)
+                       return (0);
+               if (*argtext != *mask)
+                       return (0);
+               if (*argtext == '\0')
+                       return (1);
+               argtext++;
+               mask++;
+       }
+}
+
+static int
+isdeclarationcmd(struct narg *arg)
+{
+       int have_command = 0;
+
+       if (arg == NULL)
+               return (0);
+       while (mustexpandto(arg->text, "command")) {
+               have_command = 1;
+               arg = &arg->next->narg;
+               if (arg == NULL)
+                       return (0);
+               /*
+                * To also allow "command -p" and "command --" as part of
+                * a declaration command, add code here.
+                * We do not do this, as ksh does not do it either and it
+                * is not required by POSIX.
+                */
+       }
+       return (mustexpandto(arg->text, "export") ||
+           mustexpandto(arg->text, "readonly") ||
+           (mustexpandto(arg->text, "local") &&
+               (have_command || !isfunc("local"))));
+}
+
+static void
+xtracecommand(struct arglist *varlist, struct arglist *arglist)
+{
+       struct strlist *sp;
+       char sep = 0;
+       const char *p, *ps4;
+
+       ps4 = expandstr(ps4val());
+       out2str(ps4 != NULL ? ps4 : ps4val());
+       for (sp = varlist->list ; sp ; sp = sp->next) {
+               if (sep != 0)
+                       out2c(' ');
+               p = strchr(sp->text, '=');
+               if (p != NULL) {
+                       p++;
+                       outbin(sp->text, p - sp->text, out2);
+                       out2qstr(p);
+               } else
+                       out2qstr(sp->text);
+               sep = ' ';
+       }
+       for (sp = arglist->list ; sp ; sp = sp->next) {
+               if (sep != 0)
+                       out2c(' ');
+               out2qstr(sp->text);
+               sep = ' ';
+       }
+       out2c('\n');
+       flushout(&errout);
+}
+
+/*
+ * Check if a builtin can safely be executed in the same process,
+ * even though it should be in a subshell (command substitution).
+ * Note that jobid, jobs, times and trap can show information not
+ * available in a child process; this is deliberate.
+ * The arguments should already have been expanded.
+ */
+static int
+safe_builtin(int idx, int argc, char **argv)
+{
+       if (idx == BLTINCMD || idx == COMMANDCMD || idx == ECHOCMD ||
+           idx == FALSECMD || idx == JOBIDCMD || idx == JOBSCMD ||
+           idx == KILLCMD || idx == PRINTFCMD || idx == PWDCMD ||
+           idx == TESTCMD || idx == TIMESCMD || idx == TRUECMD ||
+           idx == TYPECMD)
+               return (1);
+       if (idx == EXPORTCMD || idx == TRAPCMD || idx == ULIMITCMD ||
+           idx == UMASKCMD)
+               return (argc <= 1 || (argc == 2 && argv[1][0] == '-'));
+       if (idx == SETCMD)
+               return (argc <= 1 || (argc == 2 && (argv[1][0] == '-' ||
+                   argv[1][0] == '+') && argv[1][1] == 'o' &&
+                   argv[1][2] == '\0'));
+       return (0);
+}
+
+/*
+ * Execute a simple command.
+ * Note: This may or may not return if (flags & EV_EXIT).
+ */
+
+static void
+evalcommand(union node *cmd, int flags, struct backcmd *backcmd)
+{
+       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 *savehandler;
+       char *savecmdname;
+       struct shparam saveparam;
+       struct localvar *savelocalvars;
+       struct parsefile *savetopfile;
+       volatile int e;
+       char *lastarg;
+       int realstatus;
+       int do_clearcmdentry;
+       const char *path = pathval();
+
+       /* First expand the arguments. */
+       TRACE(("evalcommand(%p, %d) called\n", (void *)cmd, flags));
+       arglist.lastp = &arglist.list;
+       varlist.lastp = &varlist.list;
+       varflag = 1;
+       jp = NULL;
+       do_clearcmdentry = 0;
+       oexitstatus = exitstatus;
+       exitstatus = 0;
+       for (argp = cmd->ncmd.args ; argp ; argp = argp->narg.next) {
+               if (varflag && isassignment(argp->narg.text)) {
+                       expandarg(argp, varflag == 1 ? &varlist : &arglist,
+                           EXP_VARTILDE);
+                       continue;
+               } else if (varflag == 1)
+                       varflag = isdeclarationcmd(&argp->narg) ? 2 : 0;
+               expandarg(argp, &arglist, EXP_FULL | EXP_TILDE);
+       }
+       *arglist.lastp = NULL;
+       *varlist.lastp = NULL;
+       expredir(cmd->ncmd.redirect);
+       argc = 0;
+       for (sp = arglist.list ; sp ; sp = sp->next)
+               argc++;
+       /* Add one slot at the beginning for tryexec(). */
+       argv = stalloc(sizeof (char *) * (argc + 2));
+       argv++;
+
+       for (sp = arglist.list ; sp ; sp = sp->next) {
+               TRACE(("evalcommand arg: %s\n", sp->text));
+               *argv++ = sp->text;
+       }
+       *argv = NULL;
+       lastarg = NULL;
+       if (iflag && funcnest == 0 && argc > 0)
+               lastarg = argv[-1];
+       argv -= argc;
+
+       /* Print the command if xflag is set. */
+       if (xflag)
+               xtracecommand(&varlist, &arglist);
+
+       /* Now locate the command. */
+       if (argc == 0) {
+               /* Variable assignment(s) without command */
+               cmdentry.cmdtype = CMDBUILTIN;
+               cmdentry.u.index = BLTINCMD;
+               cmdentry.special = 0;
+       } else {
+               static const char PATH[] = "PATH=";
+               int cmd_flags = 0, bltinonly = 0;
+
+               /*
+                * 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;
+                               /*
+                                * On `PATH=... command`, we need to make
+                                * sure that the command isn't using the
+                                * non-updated hash table of the outer PATH
+                                * setting and we need to make sure that
+                                * the hash table isn't filled with items
+                                * from the temporary setting.
+                                *
+                                * It would be better to forbit using and
+                                * updating the table while this command
+                                * runs, by the command finding mechanism
+                                * is heavily integrated with hash handling,
+                                * so we just delete the hash before and after
+                                * the command runs. Partly deleting like
+                                * changepatch() does doesn't seem worth the
+                                * bookinging effort, since most such runs add
+                                * directories in front of the new PATH.
+                                */
+                               clearcmdentry();
+                               do_clearcmdentry = 1;
+                       }
+
+               for (;;) {
+                       if (bltinonly) {
+                               cmdentry.u.index = find_builtin(*argv, &cmdentry.special);
+                               if (cmdentry.u.index < 0) {
+                                       cmdentry.u.index = BLTINCMD;
+                                       argv--;
+                                       argc++;
+                                       break;
+                               }
+                       } else
+                               find_command(argv[0], &cmdentry, cmd_flags, path);
+                       /* implement the bltin and command builtins here */
+                       if (cmdentry.cmdtype != CMDBUILTIN)
+                               break;
+                       if (cmdentry.u.index == BLTINCMD) {
+                               if (argc == 1)
+                                       break;
+                               argv++;
+                               argc--;
+                               bltinonly = 1;
+                       } else if (cmdentry.u.index == COMMANDCMD) {
+                               if (argc == 1)
+                                       break;
+                               if (!strcmp(argv[1], "-p")) {
+                                       if (argc == 2)
+                                               break;
+                                       if (argv[2][0] == '-') {
+                                               if (strcmp(argv[2], "--"))
+                                                       break;
+                                               if (argc == 3)
+                                                       break;
+                                               argv += 3;
+                                               argc -= 3;
+                                       } else {
+                                               argv += 2;
+                                               argc -= 2;
+                                       }
+                                       path = _PATH_STDPATH;
+                                       clearcmdentry();
+                                       do_clearcmdentry = 1;
+                               } else if (!strcmp(argv[1], "--")) {
+                                       if (argc == 2)
+                                               break;
+                                       argv += 2;
+                                       argc -= 2;
+                               } else if (argv[1][0] == '-')
+                                       break;
+                               else {
+                                       argv++;
+                                       argc--;
+                               }
+                               cmd_flags |= DO_NOFUNC;
+                               bltinonly = 0;
+                       } else
+                               break;
+               }
+               /*
+                * Special builtins lose their special properties when
+                * called via 'command'.
+                */
+               if (cmd_flags & DO_NOFUNC)
+                       cmdentry.special = 0;
+       }
+
+       /* Fork off a child process if necessary. */
+       if (((cmdentry.cmdtype == CMDNORMAL || cmdentry.cmdtype == CMDUNKNOWN)
+           && ((flags & EV_EXIT) == 0 || have_traps()))
+        || ((flags & EV_BACKCMD) != 0
+           && (cmdentry.cmdtype != CMDBUILTIN ||
+                !safe_builtin(cmdentry.u.index, argc, argv)))) {
+               jp = makejob(cmd, 1);
+               mode = FORK_FG;
+               if (flags & EV_BACKCMD) {
+                       mode = FORK_NOJOB;
+                       if (pipe(pip) < 0)
+                               error("Pipe call failed: %s", strerror(errno));
+               }
+               if (cmdentry.cmdtype == CMDNORMAL &&
+                   cmd->ncmd.redirect == NULL &&
+                   varlist.list == NULL &&
+                   (mode == FORK_FG || mode == FORK_NOJOB) &&
+                   !disvforkset() && !iflag && !mflag) {
+                       vforkexecshell(jp, argv, environment(), path,
+                           cmdentry.u.index, flags & EV_BACKCMD ? pip : NULL);
+                       goto parent;
+               }
+               if (forkshell(jp, cmd, mode) != 0)
+                       goto parent;    /* at end of routine */
+               if (flags & EV_BACKCMD) {
+                       FORCEINTON;
+                       close(pip[0]);
+                       if (pip[1] != 1) {
+                               dup2(pip[1], 1);
+                               close(pip[1]);
+                       }
+                       flags &= ~EV_BACKCMD;
+               }
+               flags |= EV_EXIT;
+       }
+
+       /* This is the child process if a fork occurred. */
+       /* Execute the command. */
+       if (cmdentry.cmdtype == CMDFUNCTION) {
+#ifdef DEBUG
+               trputs("Shell function:  ");  trargs(argv);
+#endif
+               saveparam = shellparam;
+               shellparam.malloc = 0;
+               shellparam.reset = 1;
+               shellparam.nparam = argc - 1;
+               shellparam.p = argv + 1;
+               shellparam.optp = NULL;
+               shellparam.optnext = NULL;
+               INTOFF;
+               savelocalvars = localvars;
+               localvars = NULL;
+               reffunc(cmdentry.u.func);
+               savehandler = handler;
+               if (setjmp(jmploc.loc)) {
+                       freeparam(&shellparam);
+                       shellparam = saveparam;
+                       popredir();
+                       unreffunc(cmdentry.u.func);
+                       poplocalvars();
+                       localvars = savelocalvars;
+                       funcnest--;
+                       handler = savehandler;
+                       longjmp(handler->loc, 1);
+               }
+               handler = &jmploc;
+               funcnest++;
+               redirect(cmd->ncmd.redirect, REDIR_PUSH);
+               INTON;
+               for (sp = varlist.list ; sp ; sp = sp->next)
+                       mklocal(sp->text);
+               exitstatus = oexitstatus;
+               evaltree(getfuncnode(cmdentry.u.func),
+                   flags & (EV_TESTED | EV_EXIT));
+               INTOFF;
+               unreffunc(cmdentry.u.func);
+               poplocalvars();
+               localvars = savelocalvars;
+               freeparam(&shellparam);
+               shellparam = saveparam;
+               handler = savehandler;
+               funcnest--;
+               popredir();
+               INTON;
+               if (evalskip == SKIPRETURN) {
+                       evalskip = 0;
+                       skipcount = 0;
+               }
+               if (jp)
+                       exitshell(exitstatus);
+       } else if (cmdentry.cmdtype == CMDBUILTIN) {
+#ifdef DEBUG
+               trputs("builtin command:  ");  trargs(argv);
+#endif
+               mode = (cmdentry.u.index == EXECCMD)? 0 : REDIR_PUSH;
+               if (flags == EV_BACKCMD) {
+                       memout.nleft = 0;
+                       memout.nextc = memout.buf;
+                       memout.bufsize = 64;
+                       mode |= REDIR_BACKQ;
+               }
+               savecmdname = commandname;
+               savetopfile = getcurrentfile();
+               cmdenviron = varlist.list;
+               e = -1;
+               savehandler = handler;
+               if (setjmp(jmploc.loc)) {
+                       e = exception;
+                       if (e == EXINT)
+                               exitstatus = SIGINT+128;
+                       else if (e != EXEXIT)
+                               exitstatus = 2;
+                       goto cmddone;
+               }
+               handler = &jmploc;
+               redirect(cmd->ncmd.redirect, mode);
+               outclearerror(out1);
+               /*
+                * If there is no command word, redirection errors should
+                * not be fatal but assignment errors should.
+                */
+               if (argc == 0)
+                       cmdentry.special = 1;
+               listsetvar(cmdenviron, cmdentry.special ? 0 : VNOSET);
+               if (argc > 0)
+                       bltinsetlocale();
+               commandname = argv[0];
+               argptr = argv + 1;
+               nextopt_optptr = NULL;          /* initialize nextopt */
+               builtin_flags = flags;
+               exitstatus = (*builtinfunc[cmdentry.u.index])(argc, argv);
+               flushall();
+               if (outiserror(out1)) {
+                       warning("write error on stdout");
+                       if (exitstatus == 0 || exitstatus == 1)
+                               exitstatus = 2;
+               }
+cmddone:
+               if (argc > 0)
+                       bltinunsetlocale();
+               cmdenviron = NULL;
+               out1 = &output;
+               out2 = &errout;
+               freestdout();
+               handler = savehandler;
+               commandname = savecmdname;
+               if (jp)
+                       exitshell(exitstatus);
+               if (flags == EV_BACKCMD) {
+                       backcmd->buf = memout.buf;
+                       backcmd->nleft = memout.nextc - memout.buf;
+                       memout.buf = NULL;
+               }
+               if (cmdentry.u.index != EXECCMD)
+                       popredir();
+               if (e != -1) {
+                       if ((e != EXERROR && e != EXEXEC)
+                           || cmdentry.special)
+                               exraise(e);
+                       popfilesupto(savetopfile);
+                       if (flags != EV_BACKCMD)
+                               FORCEINTON;
+               }
+       } else {
+#ifdef DEBUG
+               trputs("normal command:  ");  trargs(argv);
+#endif
+               redirect(cmd->ncmd.redirect, 0);
+               for (sp = varlist.list ; sp ; sp = sp->next)
+                       setvareq(sp->text, VEXPORT|VSTACK);
+               envp = environment();
+               shellexec(argv, envp, path, cmdentry.u.index);
+               /*NOTREACHED*/
+       }
+       goto out;
+
+parent:        /* parent process gets here (if we forked) */
+       if (mode == FORK_FG) {  /* argument to fork */
+               INTOFF;
+               exitstatus = waitforjob(jp, &realstatus);
+               INTON;
+               if (iflag && loopnest > 0 && WIFSIGNALED(realstatus)) {
+                       evalskip = SKIPBREAK;
+                       skipcount = loopnest;
+               }
+       } else if (mode == FORK_NOJOB) {
+               backcmd->fd = pip[0];
+               close(pip[1]);
+               backcmd->jp = jp;
+       }
+
+out:
+       if (lastarg)
+               setvar("_", lastarg, 0);
+       if (do_clearcmdentry)
+               clearcmdentry();
+}
+
+
+
+/*
+ * 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(union node *n)
+{
+       struct cmdentry entry;
+
+       if (n && n->type == NCMD && n->ncmd.args)
+               if (goodname(n->ncmd.args->narg.text))
+                       find_command(n->ncmd.args->narg.text, &entry, 0,
+                                    pathval());
+}
+
+
+
+/*
+ * Builtin commands.  Builtin commands whose functions are closely
+ * tied to evaluation are implemented here.
+ */
+
+/*
+ * No command given, a bltin command with no arguments, or a bltin command
+ * with an invalid name.
+ */
+
+int
+bltincmd(int argc, char **argv)
+{
+       if (argc > 1) {
+               out2fmt_flush("%s: not found\n", argv[1]);
+               return 127;
+       }
+       /*
+        * Preserve exitstatus of a previous possible redirection
+        * as POSIX mandates
+        */
+       return exitstatus;
+}
+
+
+/*
+ * Handle break and continue commands.  Break, continue, and return are
+ * all handled by setting the 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(int argc, char **argv)
+{
+       long n;
+       char *end;
+
+       if (argc > 1) {
+               /* Allow arbitrarily large numbers. */
+               n = strtol(argv[1], &end, 10);
+               if (!is_digit(argv[1][0]) || *end != '\0')
+                       error("Illegal number: %s", argv[1]);
+       } else
+               n = 1;
+       if (n > loopnest)
+               n = loopnest;
+       if (n > 0) {
+               evalskip = (**argv == 'c')? SKIPCONT : SKIPBREAK;
+               skipcount = n;
+       }
+       return 0;
+}
+
+/*
+ * The `command' command.
+ */
+int
+commandcmd(int argc __unused, char **argv __unused)
+{
+       const char *path;
+       int ch;
+       int cmd = -1;
+
+       path = bltinlookup("PATH", 1);
+
+       while ((ch = nextopt("pvV")) != '\0') {
+               switch (ch) {
+               case 'p':
+                       path = _PATH_STDPATH;
+                       break;
+               case 'v':
+                       cmd = TYPECMD_SMALLV;
+                       break;
+               case 'V':
+                       cmd = TYPECMD_BIGV;
+                       break;
+               }
+       }
+
+       if (cmd != -1) {
+               if (*argptr == NULL || argptr[1] != NULL)
+                       error("wrong number of arguments");
+               return typecmd_impl(2, argptr - 1, cmd, path);
+       }
+       if (*argptr != NULL)
+               error("commandcmd bad call");
+
+       /*
+        * Do nothing successfully if no command was specified;
+        * ksh also does this.
+        */
+       return 0;
+}
+
+
+/*
+ * The return command.
+ */
+
+int
+returncmd(int argc, char **argv)
+{
+       int ret = argc > 1 ? number(argv[1]) : oexitstatus;
+
+       evalskip = SKIPRETURN;
+       skipcount = 1;
+       return ret;
+}
+
+
+int
+falsecmd(int argc __unused, char **argv __unused)
+{
+       return 1;
+}
+
+
+int
+truecmd(int argc __unused, char **argv __unused)
+{
+       return 0;
+}
+
+
+int
+execcmd(int argc, char **argv)
+{
+       /*
+        * Because we have historically not supported any options,
+        * only treat "--" specially.
+        */
+       if (argc > 1 && strcmp(argv[1], "--") == 0)
+               argc--, argv++;
+       if (argc > 1) {
+               struct strlist *sp;
+
+               iflag = 0;              /* exit on error */
+               mflag = 0;
+               optschanged();
+               for (sp = cmdenviron; sp ; sp = sp->next)
+                       setvareq(sp->text, VEXPORT|VSTACK);
+               shellexec(argv + 1, environment(), pathval(), 0);
+
+       }
+       return 0;
+}
+
+
+int
+timescmd(int argc __unused, char **argv __unused)
+{
+       struct rusage ru;
+       long shumins, shsmins, chumins, chsmins;
+       double shusecs, shssecs, chusecs, chssecs;
+
+       if (getrusage(RUSAGE_SELF, &ru) < 0)
+               return 1;
+       shumins = ru.ru_utime.tv_sec / 60;
+       shusecs = ru.ru_utime.tv_sec % 60 + ru.ru_utime.tv_usec / 1000000.;
+       shsmins = ru.ru_stime.tv_sec / 60;
+       shssecs = ru.ru_stime.tv_sec % 60 + ru.ru_stime.tv_usec / 1000000.;
+       if (getrusage(RUSAGE_CHILDREN, &ru) < 0)
+               return 1;
+       chumins = ru.ru_utime.tv_sec / 60;
+       chusecs = ru.ru_utime.tv_sec % 60 + ru.ru_utime.tv_usec / 1000000.;
+       chsmins = ru.ru_stime.tv_sec / 60;
+       chssecs = ru.ru_stime.tv_sec % 60 + ru.ru_stime.tv_usec / 1000000.;
+       out1fmt("%ldm%.3fs %ldm%.3fs\n%ldm%.3fs %ldm%.3fs\n", shumins,
+           shusecs, shsmins, shssecs, chumins, chusecs, chsmins, chssecs);
+       return 0;
+}