popen.c revision 23734 
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)
38static char sccsid[] = "@(#)popen.c	8.3 (Berkeley) 5/3/95";
39#endif /* LIBC_SCCS and not lint */
40
41#include <sys/param.h>
42#include <sys/wait.h>
43
44#include <signal.h>
45#include <errno.h>
46#include <unistd.h>
47#include <stdio.h>
48#include <stdlib.h>
49#include <string.h>
50#include <paths.h>
51
52static struct pid {
53	struct pid *next;
54	FILE *fp;
55	pid_t pid;
56} *pidlist;
57
58FILE *
59popen(command, type)
60	const char *command, *type;
61{
62	struct pid *cur;
63	FILE *iop;
64	int pdes[2], pid, twoway;
65
66	/*
67	 * Lite2 introduced two-way popen() pipes using socketpair().
68	 * FreeBSD's pipe() is bidirectional, so we use that.
69	 */
70	if (strchr(type, '+')) {
71		twoway = 1;
72		type = "r+";
73	} else  {
74		twoway = 0;
75		if ((*type != 'r' && *type != 'w') || type[1])
76			return (NULL);
77	}
78	if (pipe(pdes) < 0)
79		return (NULL);
80
81	if ((cur = malloc(sizeof(struct pid))) == NULL) {
82		(void)close(pdes[0]);
83		(void)close(pdes[1]);
84		return (NULL);
85	}
86
87	switch (pid = vfork()) {
88	case -1:			/* Error. */
89		(void)close(pdes[0]);
90		(void)close(pdes[1]);
91		free(cur);
92		return (NULL);
93		/* NOTREACHED */
94	case 0:				/* Child. */
95		if (*type == 'r') {
96			if (pdes[1] != STDOUT_FILENO) {
97				(void)dup2(pdes[1], STDOUT_FILENO);
98				(void)close(pdes[1]);
99				pdes[1] = STDOUT_FILENO;
100			}
101			(void) close(pdes[0]);
102			if (twoway && (pdes[1] != STDIN_FILENO))
103				(void)dup2(pdes[1], STDIN_FILENO);
104		} else {
105			if (pdes[0] != STDIN_FILENO) {
106				(void)dup2(pdes[0], STDIN_FILENO);
107				(void)close(pdes[0]);
108			}
109			(void)close(pdes[1]);
110		}
111		execl(_PATH_BSHELL, "sh", "-c", command, NULL);
112		_exit(127);
113		/* NOTREACHED */
114	}
115
116	/* Parent; assume fdopen can't fail. */
117	if (*type == 'r') {
118		iop = fdopen(pdes[0], type);
119		(void)close(pdes[1]);
120	} else {
121		iop = fdopen(pdes[1], type);
122		(void)close(pdes[0]);
123	}
124
125	/* Link into list of file descriptors. */
126	cur->fp = iop;
127	cur->pid =  pid;
128	cur->next = pidlist;
129	pidlist = cur;
130
131	return (iop);
132}
133
134/*
135 * pclose --
136 *	Pclose returns -1 if stream is not associated with a `popened' command,
137 *	if already `pclosed', or waitpid returns an error.
138 */
139int
140pclose(iop)
141	FILE *iop;
142{
143	register struct pid *cur, *last;
144	int omask;
145	int pstat;
146	pid_t pid;
147
148	/* Find the appropriate file pointer. */
149	for (last = NULL, cur = pidlist; cur; last = cur, cur = cur->next)
150		if (cur->fp == iop)
151			break;
152	if (cur == NULL)
153		return (-1);
154
155	(void)fclose(iop);
156
157	do {
158		pid = waitpid(cur->pid, &pstat, 0);
159	} while (pid == -1 && errno == EINTR);
160
161	/* Remove the entry from the linked list. */
162	if (last == NULL)
163		pidlist = cur->next;
164	else
165		last->next = cur->next;
166	free(cur);
167
168	return (pid == -1 ? -1 : pstat);
169}
170