eval.c

操作系统源代码

/*-
 * Copyright (c) 1991 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 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
static char sccsid[] = "@(#)eval.c	5.3 (Berkeley) 4/12/91";
#endif /* not lint */

/*
 * 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 "mystring.h"
#include <sys/types.h>
#include <signal.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 */


/* reasons for skipping commands (see comment on breakcmd routine) */
#define SKIPBREAK 1
#define SKIPCONT 2
#define SKIPFUNC 3

MKINIT 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 */


#ifdef __STDC__
STATIC void evalloop(union node *);
STATIC void evalfor(union node *);
STATIC void evalcase(union node *, int);
STATIC void evalsubshell(union node *, int);
STATIC void expredir(union node *);
STATIC void evalpipe(union node *);
STATIC void evalcommand(union node *, int, struct backcmd *);
STATIC void prehash(union node *);
#else
STATIC void evalloop();
STATIC void evalfor();
STATIC void evalcase();
STATIC void evalsubshell();
STATIC void expredir();
STATIC void evalpipe();
STATIC void evalcommand();
STATIC void prehash();
#endif



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

#ifdef mkinit
INCLUDE "eval.h"

RESET {
	evalskip = 0;
	loopnest = 0;
	funcnest = 0;
}

SHELLPROC {
	exitstatus = 0;
}
#endif



/*
 * The eval commmand.
 */

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

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


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

void
evalstring(s)
	char *s;
	{
	union node *n;
	struct stackmark smark;

	setstackmark(&smark);
	setinputstring(s, 1);
	while ((n = parsecmd(0)) != NEOF) {
		evaltree(n, 0);
		popstackmark(&smark);
	}
	popfile();
	popstackmark(&smark);
}



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

void
evaltree(n, flags)
	union node *n;
	{
	if (n == NULL) {
		TRACE(("evaltree(NULL) called\n"));
		return;
	}
	TRACE(("evaltree(0x%x: %d) called\n", (int)n, n->type));
	switch (n->type) {
	case NSEMI:
		evaltree(n->nbinary.ch1, 0);
		if (evalskip)
			goto out;
		evaltree(n->nbinary.ch2, flags);
		break;
	case NAND:
		evaltree(n->nbinary.ch1, EV_TESTED);
		if (evalskip || exitstatus != 0)
			goto out;
		evaltree(n->nbinary.ch2, flags);
		break;
	case NOR:
		evaltree(n->nbinary.ch1, EV_TESTED);
		if (evalskip || exitstatus == 0)
			goto out;
		evaltree(n->nbinary.ch2, flags);
		break;
	case NREDIR:
		expredir(n->nredir.redirect);
		redirect(n->nredir.redirect, REDIR_PUSH);
		evaltree(n->nredir.n, flags);
		popredir();
		break;
	case NSUBSHELL:
		evalsubshell(n, flags);
		break;
	case NBACKGND:
		evalsubshell(n, flags);
		break;
	case NIF: {
		int status = 0; 

		evaltree(n->nif.test, EV_TESTED);
		if (evalskip)
			goto out;
		if (exitstatus == 0) {
			evaltree(n->nif.ifpart, flags);
			status = exitstatus;
		} else if (n->nif.elsepart) {
			evaltree(n->nif.elsepart, flags);
			status = exitstatus;
		}
		exitstatus = status;
		break;
	}
	case NWHILE:
	case NUNTIL:
		evalloop(n);
		break;
	case NFOR:
		evalfor(n);
		break;
	case NCASE:
		evalcase(n, flags);
		break;
	case NDEFUN:
		defun(n->narg.text, n->narg.next);
		exitstatus = 0;
		break;
	case NPIPE:
		evalpipe(n);
		break;
	case NCMD:
		evalcommand(n, flags, (struct backcmd *)NULL);
		break;
	default:
		out1fmt("Node type = %d\n", n->type);
		flushout(&output);
		break;
	}
out:
	if (pendingsigs)
		dotrap();
	if ((flags & EV_EXIT) || (eflag && exitstatus && !(flags & EV_TESTED)))
		exitshell(exitstatus);
}


STATIC void
evalloop(n)
	union node *n;
	{
	int status;

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



STATIC void
evalfor(n)
	union node *n;
	{
	struct arglist arglist;
	union node *argp;
	struct strlist *sp;
	struct stackmark smark;

	setstackmark(&smark);
	arglist.lastp = &arglist.list;
	for (argp = n->nfor.args ; argp ; argp = argp->narg.next) {
		expandarg(argp, &arglist, 1);
		if (evalskip)
			goto out;
	}
	*arglist.lastp = NULL;

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



STATIC void
evalcase(n, flags)
	union node *n;
	{
	union node *cp;
	union node *patp;
	struct arglist arglist;
	struct stackmark smark;

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



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

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

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



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

STATIC void
expredir(n)
	union node *n;
	{
	register union node *redir;

	for (redir = n ; redir ; redir = redir->nfile.next) {
		if (redir->type == NFROM
		 || redir->type == NTO
		 || redir->type == NAPPEND) {
			struct arglist fn;
			fn.lastp = &fn.list;
			expandarg(redir->nfile.fname, &fn, 0);
			redir->nfile.expfname = fn.list->text;
		}
	}
}



/*
 * 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(n)
	union node *n;
	{
	struct job *jp;
	struct nodelist *lp;
	int pipelen;
	int prevfd;
	int pip[2];

	TRACE(("evalpipe(0x%x) called\n", (int)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;