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popen.c revision 1.1 
      1 /*
      2  * Copyright (c) 1988 The Regents of the University of California.
      3  * All rights reserved.
      4  *
      5  * This code is derived from software written by Ken Arnold and
      6  * published in UNIX Review, Vol. 6, No. 8.
      7  *
      8  * Redistribution and use in source and binary forms, with or without
      9  * modification, are permitted provided that the following conditions
     10  * are met:
     11  * 1. Redistributions of source code must retain the above copyright
     12  *    notice, this list of conditions and the following disclaimer.
     13  * 2. Redistributions in binary form must reproduce the above copyright
     14  *    notice, this list of conditions and the following disclaimer in the
     15  *    documentation and/or other materials provided with the distribution.
     16  * 3. All advertising materials mentioning features or use of this software
     17  *    must display the following acknowledgement:
     18  *	This product includes software developed by the University of
     19  *	California, Berkeley and its contributors.
     20  * 4. Neither the name of the University nor the names of its contributors
     21  *    may be used to endorse or promote products derived from this software
     22  *    without specific prior written permission.
     23  *
     24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     34  * SUCH DAMAGE.
     35  */
     36 
     37 #if defined(LIBC_SCCS) && !defined(lint)
     38 static char sccsid[] = "@(#)popen.c	5.15 (Berkeley) 2/23/91";
     39 #endif /* LIBC_SCCS and not lint */
     40 
     41 #include <sys/param.h>
     42 #include <sys/signal.h>
     43 #include <sys/wait.h>
     44 #include <errno.h>
     45 #include <stdio.h>
     46 #include <stdlib.h>
     47 #include <string.h>
     48 #include <unistd.h>
     49 #include <paths.h>
     50 
     51 static pid_t *pids;
     52 
     53 FILE *
     54 popen(program, type)
     55 	const char *program;
     56 	const char *type;
     57 {
     58 	FILE *iop;
     59 	int pdes[2], fds, pid;
     60 
     61 	if (*type != 'r' && *type != 'w' || type[1])
     62 		return (NULL);
     63 
     64 	if (pids == NULL) {
     65 		if ((fds = getdtablesize()) <= 0)
     66 			return (NULL);
     67 		if ((pids = (pid_t *)malloc((u_int)(fds * sizeof(int)))) == NULL)
     68 			return (NULL);
     69 		bzero((char *)pids, fds * sizeof(pid_t));
     70 	}
     71 	if (pipe(pdes) < 0)
     72 		return (NULL);
     73 	switch (pid = vfork()) {
     74 	case -1:			/* error */
     75 		(void) close(pdes[0]);
     76 		(void) close(pdes[1]);
     77 		return (NULL);
     78 		/* NOTREACHED */
     79 	case 0:				/* child */
     80 		if (*type == 'r') {
     81 			if (pdes[1] != STDOUT_FILENO) {
     82 				(void) dup2(pdes[1], STDOUT_FILENO);
     83 				(void) close(pdes[1]);
     84 			}
     85 			(void) close(pdes[0]);
     86 		} else {
     87 			if (pdes[0] != STDIN_FILENO) {
     88 				(void) dup2(pdes[0], STDIN_FILENO);
     89 				(void) close(pdes[0]);
     90 			}
     91 			(void) close(pdes[1]);
     92 		}
     93 		execl(_PATH_BSHELL, "sh", "-c", program, NULL);
     94 		_exit(127);
     95 		/* NOTREACHED */
     96 	}
     97 	/* parent; assume fdopen can't fail...  */
     98 	if (*type == 'r') {
     99 		iop = fdopen(pdes[0], type);
    100 		(void) close(pdes[1]);
    101 	} else {
    102 		iop = fdopen(pdes[1], type);
    103 		(void) close(pdes[0]);
    104 	}
    105 	pids[fileno(iop)] = pid;
    106 	return (iop);
    107 }
    108 
    109 int
    110 pclose(iop)
    111 	FILE *iop;
    112 {
    113 	register int fdes;
    114 	int omask;
    115 	union wait pstat;
    116 	pid_t pid;
    117 
    118 	/*
    119 	 * pclose returns -1 if stream is not associated with a
    120 	 * `popened' command, if already `pclosed', or waitpid
    121 	 * returns an error.
    122 	 */
    123 	if (pids == NULL || pids[fdes = fileno(iop)] == 0)
    124 		return (-1);
    125 	(void) fclose(iop);
    126 	omask = sigblock(sigmask(SIGINT)|sigmask(SIGQUIT)|sigmask(SIGHUP));
    127 	do {
    128 		pid = waitpid(pids[fdes], (int *) &pstat, 0);
    129 	} while (pid == -1 && errno == EINTR);
    130 	(void) sigsetmask(omask);
    131 	pids[fdes] = 0;
    132 	return (pid == -1 ? -1 : pstat.w_status);
    133 }
    134