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popen.c revision 1.9 
      1 /*
      2  * Copyright (c) 1988, 1993
      3  *	The Regents of the University of California.  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	8.1 (Berkeley) 6/4/93"; */
     39 static char *rcsid = "$Id: popen.c,v 1.9 1994/05/09 16:28:27 jtc Exp $";
     40 #endif /* LIBC_SCCS and not lint */
     41 
     42 #include <sys/param.h>
     43 #include <sys/wait.h>
     44 
     45 #include <signal.h>
     46 #include <errno.h>
     47 #include <unistd.h>
     48 #include <stdio.h>
     49 #include <stdlib.h>
     50 #include <string.h>
     51 #include <paths.h>
     52 
     53 static struct pid {
     54 	struct pid *next;
     55 	FILE *fp;
     56 	pid_t pid;
     57 } *pidlist;
     58 
     59 FILE *
     60 popen(program, type)
     61 	const char *program;
     62 	const char *type;
     63 {
     64 	struct pid *cur;
     65 	FILE *iop;
     66 	int pdes[2], pid;
     67 
     68 	if (*type != 'r' && *type != 'w' || type[1]) {
     69 		errno = EINVAL;
     70 		return (NULL);
     71 	}
     72 
     73 	if ((cur = malloc(sizeof(struct pid))) == NULL)
     74 		return (NULL);
     75 
     76 	if (pipe(pdes) < 0) {
     77 		(void)free(cur);
     78 		return (NULL);
     79 	}
     80 
     81 	switch (pid = vfork()) {
     82 	case -1:			/* Error. */
     83 		(void)close(pdes[0]);
     84 		(void)close(pdes[1]);
     85 		(void)free(cur);
     86 		return (NULL);
     87 		/* NOTREACHED */
     88 	case 0:				/* Child. */
     89 		if (*type == 'r') {
     90 			if (pdes[1] != STDOUT_FILENO) {
     91 				(void)dup2(pdes[1], STDOUT_FILENO);
     92 				(void)close(pdes[1]);
     93 			}
     94 			(void) close(pdes[0]);
     95 		} else {
     96 			if (pdes[0] != STDIN_FILENO) {
     97 				(void)dup2(pdes[0], STDIN_FILENO);
     98 				(void)close(pdes[0]);
     99 			}
    100 			(void)close(pdes[1]);
    101 		}
    102 		execl(_PATH_BSHELL, "sh", "-c", program, (char *) 0);
    103 		_exit(127);
    104 		/* NOTREACHED */
    105 	}
    106 
    107 	/* Parent; assume fdopen can't fail. */
    108 	if (*type == 'r') {
    109 		iop = fdopen(pdes[0], type);
    110 		(void)close(pdes[1]);
    111 	} else {
    112 		iop = fdopen(pdes[1], type);
    113 		(void)close(pdes[0]);
    114 	}
    115 
    116 	/* Link into list of file descriptors. */
    117 	cur->fp = iop;
    118 	cur->pid =  pid;
    119 	cur->next = pidlist;
    120 	pidlist = cur;
    121 
    122 	return (iop);
    123 }
    124 
    125 /*
    126  * pclose --
    127  *	Pclose returns -1 if stream is not associated with a `popened' command,
    128  *	if already `pclosed', or waitpid returns an error.
    129  */
    130 int
    131 pclose(iop)
    132 	FILE *iop;
    133 {
    134 	register struct pid *cur, *last;
    135 	int pstat;
    136 	pid_t pid;
    137 
    138 	(void)fclose(iop);
    139 
    140 	/* Find the appropriate file pointer. */
    141 	for (last = NULL, cur = pidlist; cur; last = cur, cur = cur->next)
    142 		if (cur->fp == iop)
    143 			break;
    144 	if (cur == NULL)
    145 		return (-1);
    146 
    147 	do {
    148 		pid = waitpid(cur->pid, &pstat, 0);
    149 	} while (pid == -1 && errno == EINTR);
    150 
    151 	/* Remove the entry from the linked list. */
    152 	if (last == NULL)
    153 		pidlist = cur->next;
    154 	else
    155 		last->next = cur->next;
    156 	free(cur);
    157 
    158 	return (pid == -1 ? -1 : pstat);
    159 }
    160