redir.c

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/*-
 * 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[] = "@(#)redir.c     5.1 (Berkeley) 3/7/91";
#endif /* not lint */

/*
 * Code for dealing with input/output redirection.
 */

#include "shell.h"
#include "nodes.h"
#include "jobs.h"
#include "expand.h"
#include "redir.h"
#include "eval.h"
#include "output.h"
#include "memalloc.h"
#include "error.h"
#include <sys/types.h>
#include <signal.h>
#include <fcntl.h>
#include <errno.h>
#include <limits.h>


#define EMPTY -2                /* marks an unused slot in redirtab */
#define PIPESIZE 4096           /* amount of buffering in a pipe */


MKINIT
struct redirtab {
        struct redirtab *next;
        short renamed[10];
};


MKINIT struct redirtab *redirlist;

/* We keep track of whether or not fd0 has been redirected.  This is for
   background commands, where we want to redirect fd0 to /dev/null only
   if it hasn't already been redirected.  */
int fd0_redirected = 0;

#ifdef __STDC__
STATIC void openredirect(union node *, char *);
STATIC int openhere(union node *);
#else
STATIC void openredirect();
STATIC int openhere();
#endif



/*
 * Process a list of redirection commands.  If the REDIR_PUSH flag is set,
 * old file descriptors are stashed away so that the redirection can be
 * undone by calling popredir.  If the REDIR_BACKQ flag is set, then the
 * standard output, and the standard error if it becomes a duplicate of
 * stdout, is saved in memory.
 */

void
redirect(redir, flags)
        union node *redir;
        int flags;
        {
        union node *n;
        struct redirtab *sv;
        int i;
        int fd;
        char memory[10];                /* file descriptors to write to memory */

        for (i = 10 ; --i >= 0 ; )
                memory[i] = 0;
        memory[1] = flags & REDIR_BACKQ;
        if (flags & REDIR_PUSH) {
                sv = ckmalloc(sizeof (struct redirtab));
                for (i = 0 ; i < 10 ; i++)
                        sv->renamed[i] = EMPTY;
                sv->next = redirlist;
                redirlist = sv;
        }
        for (n = redir ; n ; n = n->nfile.next) {
                fd = n->nfile.fd;
                if ((flags & REDIR_PUSH) && sv->renamed[fd] == EMPTY) {
                        INTOFF;
                        if ((i = copyfd(fd, 10)) != EMPTY) {
                                sv->renamed[fd] = i;
                                close(fd);
                        }
                        INTON;
                        if (i == EMPTY)
                                error("Out of file descriptors");
                } else {
                        close(fd);
                }
                if (fd == 0)
                        fd0_redirected++;
                openredirect(n, memory);
        }
        if (memory[1])
                out1 = &memout;
        if (memory[2])
                out2 = &memout;
}


STATIC void
openredirect(redir, memory)
        union node *redir;
        char memory[10];
        {
        int fd = redir->nfile.fd;
        char *fname;
        int f;

        /* Assume redirection succeeds. */
        exitstatus = 0;

        /*
         * We suppress interrupts so that we won't leave open file
         * descriptors around.  This may not be such a good idea because
         * an open of a device or a fifo can block indefinitely.
         */
        INTOFF;
        memory[fd] = 0;
        switch (redir->nfile.type) {
        case NFROM:
                fname = redir->nfile.expfname;
                if ((f = open(fname, O_RDONLY)) < 0)
                        error("cannot open %s: %s", fname, errmsg(errno, E_OPEN));
movefd:
                if (f != fd) {
                        copyfd(f, fd);
                        close(f);
                }
                break;
        case NTO:
                fname = redir->nfile.expfname;
#ifdef O_CREAT
                if ((f = open(fname, O_WRONLY|O_CREAT|O_TRUNC, 0666)) < 0)
                        error("cannot create %s: %s", fname, errmsg(errno, E_CREAT));
#else
                if ((f = creat(fname, 0666)) < 0)
                        error("cannot create %s: %s", fname, errmsg(errno, E_CREAT));
#endif
                goto movefd;
        case NAPPEND:
                fname = redir->nfile.expfname;
#ifdef O_APPEND
                if ((f = open(fname, O_WRONLY|O_CREAT|O_APPEND, 0666)) < 0)
                        error("cannot create %s: %s", fname, errmsg(errno, E_CREAT));
#else
                if ((f = open(fname, O_WRONLY)) < 0
                 && (f = creat(fname, 0666)) < 0)
                        error("cannot create %s: %s", fname, errmsg(errno, E_CREAT));
                lseek(f, 0L, 2);
#endif
                goto movefd;
        case NTOFD:
        case NFROMFD:
                if (redir->ndup.dupfd >= 0) {   /* if not ">&-" */
                        if (memory[redir->ndup.dupfd])
                                memory[fd] = 1;
                        else
                                copyfd(redir->ndup.dupfd, fd);
                }
                break;
        case NHERE:
        case NXHERE:
                f = openhere(redir);
                goto movefd;
        default:
                abort();
        }
        INTON;
}


/*
 * Handle here documents.  Normally we fork off a process to write the
 * data to a pipe.  If the document is short, we can stuff the data in
 * the pipe without forking.
 */

STATIC int
openhere(redir)
        union node *redir;
        {
        int pip[2];
        int len;

        if (pipe(pip) < 0)
                error("Pipe call failed");
        if (redir->type == NHERE) {
                len = strlen(redir->nhere.doc->narg.text);
                if (len <= PIPESIZE) {
                        xwrite(pip[1], redir->nhere.doc->narg.text, len);
                        goto out;
                }
        }
        if (forkshell((struct job *)NULL, (union node *)NULL, FORK_NOJOB) == 0) {
                close(pip[0]);
                signal(SIGINT, SIG_IGN);
                signal(SIGQUIT, SIG_IGN);
                signal(SIGHUP, SIG_IGN);
#ifdef SIGTSTP
                signal(SIGTSTP, SIG_IGN);
#endif
                signal(SIGPIPE, SIG_DFL);
                if (redir->type == NHERE)
                        xwrite(pip[1], redir->nhere.doc->narg.text, len);
                else
                        expandhere(redir->nhere.doc, pip[1]);
                _exit(0);
        }
out:
        close(pip[1]);
        return pip[0];
}



/*
 * Undo the effects of the last redirection.
 */

void
popredir() {
        register struct redirtab *rp = redirlist;
        int i;

        for (i = 0 ; i < 10 ; i++) {
                if (rp->renamed[i] != EMPTY) {
                        if (i == 0)
                                fd0_redirected--;
                        close(i);
                        if (rp->renamed[i] >= 0) {
                                copyfd(rp->renamed[i], i);
                                close(rp->renamed[i]);
                        }
                }
        }
        INTOFF;
        redirlist = rp->next;
        ckfree(rp);
        INTON;
}



/*
 * Undo all redirections.  Called on error or interrupt.
 */

#ifdef mkinit

INCLUDE "redir.h"

RESET {
        while (redirlist)
                popredir();
}

SHELLPROC {
        clearredir();
}

#endif


/*
 * Discard all saved file descriptors.
 */

void
clearredir() {
        register struct redirtab *rp;
        int i;

        for (rp = redirlist ; rp ; rp = rp->next) {
                for (i = 0 ; i < 10 ; i++) {
                        if (rp->renamed[i] >= 0) {
                                close(rp->renamed[i]);
                        }
                        rp->renamed[i] = EMPTY;
                }
        }
}



/*
 * Copy a file descriptor, like the F_DUPFD option of fcntl.  Returns -1
 * if the source file descriptor is closed, EMPTY if there are no unused
 * file descriptors left.
 */

int
copyfd(from, to) {
#ifdef F_DUPFD
        int newfd;

        newfd = fcntl(from, F_DUPFD, to);
        if (newfd < 0 && errno == EMFILE)
                return EMPTY;
        return newfd;
#else
        char toclose[32];
        int i;
        int newfd;
        int e;

        for (i = 0 ; i < to ; i++)
                toclose[i] = 0;
        INTOFF;
        while ((newfd = dup(from)) >= 0 && newfd < to)
                toclose[newfd] = 1;
        e = errno;
        for (i = 0 ; i < to ; i++) {
                if (toclose[i])
                        close(i);
        }
        INTON;
        if (newfd < 0 && e == EMFILE)
                return EMPTY;
        return newfd;
#endif
}

/* Return true if fd 0 has already been redirected at least once.  */
int
fd0_redirected_p () {
        return fd0_redirected != 0;
}

---