popen.c revision 40367 
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
52extern char **environ;
53
54static struct pid {
55	struct pid *next;
56	FILE *fp;
57	pid_t pid;
58} *pidlist;
59
60FILE *
61popen(command, type)
62	const char *command, *type;
63{
64	struct pid *cur;
65	FILE *iop;
66	int pdes[2], pid, twoway;
67	char *argv[4];
68	struct pid *p;
69
70	/*
71	 * Lite2 introduced two-way popen() pipes using socketpair().
72	 * FreeBSD's pipe() is bidirectional, so we use that.
73	 */
74	if (strchr(type, '+')) {
75		twoway = 1;
76		type = "r+";
77	} else  {
78		twoway = 0;
79		if ((*type != 'r' && *type != 'w') || type[1])
80			return (NULL);
81	}
82	if (pipe(pdes) < 0)
83		return (NULL);
84
85	if ((cur = malloc(sizeof(struct pid))) == NULL) {
86		(void)close(pdes[0]);
87		(void)close(pdes[1]);
88		return (NULL);
89	}
90
91	argv[0] = "sh";
92	argv[1] = "-c";
93	argv[2] = (char *)command;
94	argv[3] = NULL;
95
96	switch (pid = vfork()) {
97	case -1:			/* Error. */
98		(void)close(pdes[0]);
99		(void)close(pdes[1]);
100		free(cur);
101		return (NULL);
102		/* NOTREACHED */
103	case 0:				/* Child. */
104		if (*type == 'r') {
105			/*
106			 * The dup2() to STDIN_FILENO is repeated to avoid
107			 * writing to pdes[1], which might corrupt the
108			 * parent's copy.  This isn't good enough in
109			 * general, since the _exit() is no return, so
110			 * the compiler is free to corrupt all the local
111			 * variables.
112			 */
113			(void) close(pdes[0]);
114			if (pdes[1] != STDOUT_FILENO) {
115				(void)dup2(pdes[1], STDOUT_FILENO);
116				(void)close(pdes[1]);
117				if (twoway)
118					(void)dup2(STDOUT_FILENO, STDIN_FILENO);
119			} else if (twoway && (pdes[1] != STDIN_FILENO))
120				(void)dup2(pdes[1], STDIN_FILENO);
121		} else {
122			if (pdes[0] != STDIN_FILENO) {
123				(void)dup2(pdes[0], STDIN_FILENO);
124				(void)close(pdes[0]);
125			}
126			(void)close(pdes[1]);
127		}
128		for (p = pidlist; p; p = p->next) {
129			(void)close(fileno(p->fp));
130		}
131		execve(_PATH_BSHELL, argv, environ);
132		_exit(127);
133		/* NOTREACHED */
134	}
135
136	/* Parent; assume fdopen can't fail. */
137	if (*type == 'r') {
138		iop = fdopen(pdes[0], type);
139		(void)close(pdes[1]);
140	} else {
141		iop = fdopen(pdes[1], type);
142		(void)close(pdes[0]);
143	}
144
145	/* Link into list of file descriptors. */
146	cur->fp = iop;
147	cur->pid =  pid;
148	cur->next = pidlist;
149	pidlist = cur;
150
151	return (iop);
152}
153
154/*
155 * pclose --
156 *	Pclose returns -1 if stream is not associated with a `popened' command,
157 *	if already `pclosed', or waitpid returns an error.
158 */
159int
160pclose(iop)
161	FILE *iop;
162{
163	register struct pid *cur, *last;
164	int omask;
165	int pstat;
166	pid_t pid;
167
168	/* Find the appropriate file pointer. */
169	for (last = NULL, cur = pidlist; cur; last = cur, cur = cur->next)
170		if (cur->fp == iop)
171			break;
172	if (cur == NULL)
173		return (-1);
174
175	(void)fclose(iop);
176
177	do {
178		pid = waitpid(cur->pid, &pstat, 0);
179	} while (pid == -1 && errno == EINTR);
180
181	/* Remove the entry from the linked list. */
182	if (last == NULL)
183		pidlist = cur->next;
184	else
185		last->next = cur->next;
186	free(cur);
187
188	return (pid == -1 ? -1 : pstat);
189}
190