popen.c revision 192926 
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 * 4. Neither the name of the University nor the names of its contributors
17 *    may be used to endorse or promote products derived from this software
18 *    without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33#if defined(LIBC_SCCS) && !defined(lint)
34static char sccsid[] = "@(#)popen.c	8.3 (Berkeley) 5/3/95";
35#endif /* LIBC_SCCS and not lint */
36#include <sys/cdefs.h>
37__FBSDID("$FreeBSD: head/lib/libc/gen/popen.c 192926 2009-05-27 19:28:04Z ed $");
38
39#include "namespace.h"
40#include <sys/param.h>
41#include <sys/queue.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#include <pthread.h>
52#include "un-namespace.h"
53#include "libc_private.h"
54
55extern char **environ;
56
57struct pid {
58	SLIST_ENTRY(pid) next;
59	FILE *fp;
60	pid_t pid;
61};
62static SLIST_HEAD(, pid) pidlist = SLIST_HEAD_INITIALIZER(pidlist);
63static pthread_mutex_t pidlist_mutex = PTHREAD_MUTEX_INITIALIZER;
64
65#define	THREAD_LOCK()	if (__isthreaded) _pthread_mutex_lock(&pidlist_mutex)
66#define	THREAD_UNLOCK()	if (__isthreaded) _pthread_mutex_unlock(&pidlist_mutex)
67
68FILE *
69popen(command, type)
70	const char *command, *type;
71{
72	struct pid *cur;
73	FILE *iop;
74	int pdes[2], pid, twoway;
75	char *argv[4];
76	struct pid *p;
77
78	/*
79	 * Lite2 introduced two-way popen() pipes using _socketpair().
80	 * FreeBSD's pipe() is bidirectional, so we use that.
81	 */
82	if (strchr(type, '+')) {
83		twoway = 1;
84		type = "r+";
85	} else  {
86		twoway = 0;
87		if ((*type != 'r' && *type != 'w') || type[1])
88			return (NULL);
89	}
90	if (pipe(pdes) < 0)
91		return (NULL);
92
93	if ((cur = malloc(sizeof(struct pid))) == NULL) {
94		(void)_close(pdes[0]);
95		(void)_close(pdes[1]);
96		return (NULL);
97	}
98
99	argv[0] = "sh";
100	argv[1] = "-c";
101	argv[2] = (char *)command;
102	argv[3] = NULL;
103
104	THREAD_LOCK();
105	switch (pid = vfork()) {
106	case -1:			/* Error. */
107		THREAD_UNLOCK();
108		(void)_close(pdes[0]);
109		(void)_close(pdes[1]);
110		free(cur);
111		return (NULL);
112		/* NOTREACHED */
113	case 0:				/* Child. */
114		if (*type == 'r') {
115			/*
116			 * The _dup2() to STDIN_FILENO is repeated to avoid
117			 * writing to pdes[1], which might corrupt the
118			 * parent's copy.  This isn't good enough in
119			 * general, since the _exit() is no return, so
120			 * the compiler is free to corrupt all the local
121			 * variables.
122			 */
123			(void)_close(pdes[0]);
124			if (pdes[1] != STDOUT_FILENO) {
125				(void)_dup2(pdes[1], STDOUT_FILENO);
126				(void)_close(pdes[1]);
127				if (twoway)
128					(void)_dup2(STDOUT_FILENO, STDIN_FILENO);
129			} else if (twoway && (pdes[1] != STDIN_FILENO))
130				(void)_dup2(pdes[1], STDIN_FILENO);
131		} else {
132			if (pdes[0] != STDIN_FILENO) {
133				(void)_dup2(pdes[0], STDIN_FILENO);
134				(void)_close(pdes[0]);
135			}
136			(void)_close(pdes[1]);
137		}
138		SLIST_FOREACH(p, &pidlist, next)
139			(void)_close(fileno(p->fp));
140		_execve(_PATH_BSHELL, argv, environ);
141		_exit(127);
142		/* NOTREACHED */
143	}
144	THREAD_UNLOCK();
145
146	/* Parent; assume fdopen can't fail. */
147	if (*type == 'r') {
148		iop = fdopen(pdes[0], type);
149		(void)_close(pdes[1]);
150	} else {
151		iop = fdopen(pdes[1], type);
152		(void)_close(pdes[0]);
153	}
154
155	/* Link into list of file descriptors. */
156	cur->fp = iop;
157	cur->pid = pid;
158	THREAD_LOCK();
159	SLIST_INSERT_HEAD(&pidlist, cur, next);
160	THREAD_UNLOCK();
161
162	return (iop);
163}
164
165/*
166 * pclose --
167 *	Pclose returns -1 if stream is not associated with a `popened' command,
168 *	if already `pclosed', or waitpid returns an error.
169 */
170int
171pclose(iop)
172	FILE *iop;
173{
174	struct pid *cur, *last = NULL;
175	int pstat;
176	pid_t pid;
177
178	/*
179	 * Find the appropriate file pointer and remove it from the list.
180	 */
181	THREAD_LOCK();
182	SLIST_FOREACH(cur, &pidlist, next) {
183		if (cur->fp == iop)
184			break;
185		last = cur;
186	}
187	if (cur == NULL) {
188		THREAD_UNLOCK();
189		return (-1);
190	}
191	if (last == NULL)
192		SLIST_REMOVE_HEAD(&pidlist, next);
193	else
194		SLIST_REMOVE_AFTER(last, next);
195	THREAD_UNLOCK();
196
197	(void)fclose(iop);
198
199	do {
200		pid = _wait4(cur->pid, &pstat, 0, (struct rusage *)0);
201	} while (pid == -1 && errno == EINTR);
202
203	free(cur);
204
205	return (pid == -1 ? -1 : pstat);
206}
207