popen.c revision 40191 
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 = fork()) {
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			/*
97			 * The dup2() to STDIN_FILENO is repeated to avoid
98			 * writing to pdes[1], which might corrupt the
99			 * parent's copy.  This isn't good enough in
100			 * general, since the _exit() is no return, so
101			 * the compiler is free to corrupt all the local
102			 * variables.
103			 */
104			(void) close(pdes[0]);
105			if (pdes[1] != STDOUT_FILENO) {
106				(void)dup2(pdes[1], STDOUT_FILENO);
107				(void)close(pdes[1]);
108				if (twoway)
109					(void)dup2(STDOUT_FILENO, STDIN_FILENO);
110			} else if (twoway && (pdes[1] != STDIN_FILENO))
111				(void)dup2(pdes[1], STDIN_FILENO);
112		} else {
113			if (pdes[0] != STDIN_FILENO) {
114				(void)dup2(pdes[0], STDIN_FILENO);
115				(void)close(pdes[0]);
116			}
117			(void)close(pdes[1]);
118		}
119		execl(_PATH_BSHELL, "sh", "-c", command, NULL);
120		_exit(127);
121		/* NOTREACHED */
122	}
123
124	/* Parent; assume fdopen can't fail. */
125	if (*type == 'r') {
126		iop = fdopen(pdes[0], type);
127		(void)close(pdes[1]);
128	} else {
129		iop = fdopen(pdes[1], type);
130		(void)close(pdes[0]);
131	}
132
133	/* Link into list of file descriptors. */
134	cur->fp = iop;
135	cur->pid =  pid;
136	cur->next = pidlist;
137	pidlist = cur;
138
139	return (iop);
140}
141
142/*
143 * pclose --
144 *	Pclose returns -1 if stream is not associated with a `popened' command,
145 *	if already `pclosed', or waitpid returns an error.
146 */
147int
148pclose(iop)
149	FILE *iop;
150{
151	register struct pid *cur, *last;
152	int omask;
153	int pstat;
154	pid_t pid;
155
156	/* Find the appropriate file pointer. */
157	for (last = NULL, cur = pidlist; cur; last = cur, cur = cur->next)
158		if (cur->fp == iop)
159			break;
160	if (cur == NULL)
161		return (-1);
162
163	(void)fclose(iop);
164
165	do {
166		pid = waitpid(cur->pid, &pstat, 0);
167	} while (pid == -1 && errno == EINTR);
168
169	/* Remove the entry from the linked list. */
170	if (last == NULL)
171		pidlist = cur->next;
172	else
173		last->next = cur->next;
174	free(cur);
175
176	return (pid == -1 ? -1 : pstat);
177}
178