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popen.c revision 1.12 
      1 /*	$NetBSD: popen.c,v 1.12 1996/06/29 00:51:49 jtc Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1988, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * This code is derived from software written by Ken Arnold and
      8  * published in UNIX Review, Vol. 6, No. 8.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. All advertising materials mentioning features or use of this software
     19  *    must display the following acknowledgement:
     20  *	This product includes software developed by the University of
     21  *	California, Berkeley and its contributors.
     22  * 4. Neither the name of the University nor the names of its contributors
     23  *    may be used to endorse or promote products derived from this software
     24  *    without specific prior written permission.
     25  *
     26  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     27  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     28  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     29  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     30  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     31  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     32  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     33  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     34  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     35  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     36  * SUCH DAMAGE.
     37  */
     38 
     39 #if defined(LIBC_SCCS) && !defined(lint)
     40 #if 0
     41 static char sccsid[] = "@(#)popen.c	8.1 (Berkeley) 6/4/93";
     42 #else
     43 static char rcsid[] = "$NetBSD: popen.c,v 1.12 1996/06/29 00:51:49 jtc Exp $";
     44 #endif
     45 #endif /* LIBC_SCCS and not lint */
     46 
     47 #include <sys/param.h>
     48 #include <sys/wait.h>
     49 
     50 #include <signal.h>
     51 #include <errno.h>
     52 #include <unistd.h>
     53 #include <stdio.h>
     54 #include <stdlib.h>
     55 #include <string.h>
     56 #include <paths.h>
     57 
     58 static struct pid {
     59 	struct pid *next;
     60 	FILE *fp;
     61 	pid_t pid;
     62 } *pidlist;
     63 
     64 FILE *
     65 popen(program, type)
     66 	const char *program;
     67 	const char *type;
     68 {
     69 	struct pid *cur;
     70 	FILE *iop;
     71 	int pdes[2], pid;
     72 
     73 	if (*type != 'r' && *type != 'w' || type[1]) {
     74 		errno = EINVAL;
     75 		return (NULL);
     76 	}
     77 
     78 	if ((cur = malloc(sizeof(struct pid))) == NULL)
     79 		return (NULL);
     80 
     81 	if (pipe(pdes) < 0) {
     82 		free(cur);
     83 		return (NULL);
     84 	}
     85 
     86 	switch (pid = vfork()) {
     87 	case -1:			/* Error. */
     88 		(void)close(pdes[0]);
     89 		(void)close(pdes[1]);
     90 		free(cur);
     91 		return (NULL);
     92 		/* NOTREACHED */
     93 	case 0:				/* Child. */
     94 		if (*type == 'r') {
     95 			if (pdes[1] != STDOUT_FILENO) {
     96 				(void)dup2(pdes[1], STDOUT_FILENO);
     97 				(void)close(pdes[1]);
     98 			}
     99 			(void) close(pdes[0]);
    100 		} else {
    101 			if (pdes[0] != STDIN_FILENO) {
    102 				(void)dup2(pdes[0], STDIN_FILENO);
    103 				(void)close(pdes[0]);
    104 			}
    105 			(void)close(pdes[1]);
    106 		}
    107 
    108 		/* POSIX.2 B.3.2.2 "popen() shall ensure that any streams
    109 		   from previous popen() calls that remain open in the
    110 		   parent process are closed in the new child process. */
    111 		for (cur = pidlist; cur; cur = cur->next)
    112 			close(fileno(cur->fp));
    113 
    114 		execl(_PATH_BSHELL, "sh", "-c", program, NULL);
    115 		_exit(127);
    116 		/* NOTREACHED */
    117 	}
    118 
    119 	/* Parent; assume fdopen can't fail. */
    120 	if (*type == 'r') {
    121 		iop = fdopen(pdes[0], type);
    122 		(void)close(pdes[1]);
    123 	} else {
    124 		iop = fdopen(pdes[1], type);
    125 		(void)close(pdes[0]);
    126 	}
    127 
    128 	/* Link into list of file descriptors. */
    129 	cur->fp = iop;
    130 	cur->pid =  pid;
    131 	cur->next = pidlist;
    132 	pidlist = cur;
    133 
    134 	return (iop);
    135 }
    136 
    137 /*
    138  * pclose --
    139  *	Pclose returns -1 if stream is not associated with a `popened' command,
    140  *	if already `pclosed', or waitpid returns an error.
    141  */
    142 int
    143 pclose(iop)
    144 	FILE *iop;
    145 {
    146 	register struct pid *cur, *last;
    147 	int pstat;
    148 	pid_t pid;
    149 
    150 	(void)fclose(iop);
    151 
    152 	/* Find the appropriate file pointer. */
    153 	for (last = NULL, cur = pidlist; cur; last = cur, cur = cur->next)
    154 		if (cur->fp == iop)
    155 			break;
    156 	if (cur == NULL)
    157 		return (-1);
    158 
    159 	do {
    160 		pid = waitpid(cur->pid, &pstat, 0);
    161 	} while (pid == -1 && errno == EINTR);
    162 
    163 	/* Remove the entry from the linked list. */
    164 	if (last == NULL)
    165 		pidlist = cur->next;
    166 	else
    167 		last->next = cur->next;
    168 	free(cur);
    169 
    170 	return (pid == -1 ? -1 : pstat);
    171 }
    172