popen.c

/*
 * Copyright (c) 1988 The Regents of the University of California.
 *               with modifications from Paul Mathieu
 * All rights reserved.
 *
 * 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.
 */

#include <errno.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <strings.h>
#include <sys/wait.h>
#include <unistd.h>

static int *pids;

FILE * popen(const char* program, const char* type)
{
    FILE *iop;
    int pdes[2], fds, pid;

    if ((*type != 'r' && *type != 'w') || type[1])
        return (NULL);

    if (pids == NULL) {
        if ((fds = getdtablesize()) <= 0)
            return (NULL);
        if ((pids = (int *)malloc(fds * sizeof(int))) == NULL)
            return (NULL);
        bzero((char *)pids, fds * sizeof(int));
    }
    if (pipe(pdes) < 0)
        return (NULL);
    switch (pid = vfork()) {
    case -1:            /* error */
        (void) close(pdes[0]);
        (void) close(pdes[1]);
        return (NULL);
        /* NOTREACHED */
    case 0:             /* child */
        if (*type == 'r') {
            if (pdes[1] != fileno(stdout)) {
                (void) dup2(pdes[1], fileno(stdout));
                (void) close(pdes[1]);
            }
            (void) close(pdes[0]);
        } else {
            if (pdes[0] != fileno(stdin)) {
                (void) dup2(pdes[0], fileno(stdin));
                (void) close(pdes[0]);
            }
            (void) close(pdes[1]);
        }
        execl("/bin/sh", "sh", "-c", program, NULL);
        _exit(127);
        /* NOTREACHED */
    }
    /* parent; assume fdopen can't fail...  */
    if (*type == 'r') {
        iop = fdopen(pdes[0], type);
        (void) close(pdes[1]);
    } else {
        iop = fdopen(pdes[1], type);
        (void) close(pdes[0]);
    }
    pids[fileno(iop)] = pid;
    return (iop);
}

int pclose(FILE* iop)
{
    int fdes;
    sigset_t omask, nmask;
    union wait pstat;
    int pid;

    /*
     * pclose returns -1 if stream is not associated with a
     * `popened' command, if already `pclosed', or waitpid
     * returns an error.
     */
    if (pids == NULL || pids[fdes = fileno(iop)] == 0)
        return (-1);
    (void) fclose(iop);
    sigemptyset(&nmask);
    sigaddset(&nmask, SIGINT);
    sigaddset(&nmask, SIGQUIT);
    sigaddset(&nmask, SIGHUP);
    (void) sigprocmask(SIG_BLOCK, &nmask, &omask);
    do {
        pid = waitpid(pids[fdes], (int *) &pstat, 0);
    } while (pid == -1 && errno == EINTR);
    (void) sigprocmask(SIG_SETMASK, &omask, NULL);
    pids[fdes] = 0;
    return (pid == -1 ? -1 : pstat.w_status);
}