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popen.c revision 1.9.4.1 
      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 1.9.4.1 1995/05/02 19:34:57 jtc Exp $";
     40 #endif /* LIBC_SCCS and not lint */
     41 
     42 #include "namespace.h"
     43 #include <sys/param.h>
     44 #include <sys/wait.h>
     45 
     46 #include <signal.h>
     47 #include <errno.h>
     48 #include <unistd.h>
     49 #include <stdio.h>
     50 #include <stdlib.h>
     51 #include <string.h>
     52 #include <paths.h>
     53 
     54 static struct pid {
     55 	struct pid *next;
     56 	FILE *fp;
     57 	pid_t pid;
     58 } *pidlist;
     59 
     60 FILE *
     61 popen(program, type)
     62 	const char *program;
     63 	const char *type;
     64 {
     65 	struct pid *cur;
     66 	FILE *iop;
     67 	int pdes[2], pid;
     68 
     69 	if (*type != 'r' && *type != 'w' || type[1]) {
     70 		errno = EINVAL;
     71 		return (NULL);
     72 	}
     73 
     74 	if ((cur = malloc(sizeof(struct pid))) == NULL)
     75 		return (NULL);
     76 
     77 	if (pipe(pdes) < 0) {
     78 		(void)free(cur);
     79 		return (NULL);
     80 	}
     81 
     82 	switch (pid = vfork()) {
     83 	case -1:			/* Error. */
     84 		(void)close(pdes[0]);
     85 		(void)close(pdes[1]);
     86 		(void)free(cur);
     87 		return (NULL);
     88 		/* NOTREACHED */
     89 	case 0:				/* Child. */
     90 		if (*type == 'r') {
     91 			if (pdes[1] != STDOUT_FILENO) {
     92 				(void)dup2(pdes[1], STDOUT_FILENO);
     93 				(void)close(pdes[1]);
     94 			}
     95 			(void) close(pdes[0]);
     96 		} else {
     97 			if (pdes[0] != STDIN_FILENO) {
     98 				(void)dup2(pdes[0], STDIN_FILENO);
     99 				(void)close(pdes[0]);
    100 			}
    101 			(void)close(pdes[1]);
    102 		}
    103 		execl(_PATH_BSHELL, "sh", "-c", program, (char *) 0);
    104 		_exit(127);
    105 		/* NOTREACHED */
    106 	}
    107 
    108 	/* Parent; assume fdopen can't fail. */
    109 	if (*type == 'r') {
    110 		iop = fdopen(pdes[0], type);
    111 		(void)close(pdes[1]);
    112 	} else {
    113 		iop = fdopen(pdes[1], type);
    114 		(void)close(pdes[0]);
    115 	}
    116 
    117 	/* Link into list of file descriptors. */
    118 	cur->fp = iop;
    119 	cur->pid =  pid;
    120 	cur->next = pidlist;
    121 	pidlist = cur;
    122 
    123 	return (iop);
    124 }
    125 
    126 /*
    127  * pclose --
    128  *	Pclose returns -1 if stream is not associated with a `popened' command,
    129  *	if already `pclosed', or waitpid returns an error.
    130  */
    131 int
    132 pclose(iop)
    133 	FILE *iop;
    134 {
    135 	register struct pid *cur, *last;
    136 	int pstat;
    137 	pid_t pid;
    138 
    139 	(void)fclose(iop);
    140 
    141 	/* Find the appropriate file pointer. */
    142 	for (last = NULL, cur = pidlist; cur; last = cur, cur = cur->next)
    143 		if (cur->fp == iop)
    144 			break;
    145 	if (cur == NULL)
    146 		return (-1);
    147 
    148 	do {
    149 		pid = waitpid(cur->pid, &pstat, 0);
    150 	} while (pid == -1 && errno == EINTR);
    151 
    152 	/* Remove the entry from the linked list. */
    153 	if (last == NULL)
    154 		pidlist = cur->next;
    155 	else
    156 		last->next = cur->next;
    157 	free(cur);
    158 
    159 	return (pid == -1 ? -1 : pstat);
    160 }
    161