popen.c revision 8870 
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	8.1 (Berkeley) 6/4/93";
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(program, type)
60	const char *program;
61	const char *type;
62{
63	struct pid *cur;
64	FILE *iop;
65	int pdes[2], pid;
66
67	if (*type != 'r' && *type != 'w' || type[1])
68		return (NULL);
69
70	if ((cur = malloc(sizeof(struct pid))) == NULL)
71		return (NULL);
72
73	if (pipe(pdes) < 0) {
74		(void)free(cur);
75		return (NULL);
76	}
77
78	switch (pid = vfork()) {
79	case -1:			/* Error. */
80		(void)close(pdes[0]);
81		(void)close(pdes[1]);
82		(void)free(cur);
83		return (NULL);
84		/* NOTREACHED */
85	case 0:				/* Child. */
86		if (*type == 'r') {
87			if (pdes[1] != STDOUT_FILENO) {
88				(void)dup2(pdes[1], STDOUT_FILENO);
89				(void)close(pdes[1]);
90			}
91			(void) close(pdes[0]);
92		} else {
93			if (pdes[0] != STDIN_FILENO) {
94				(void)dup2(pdes[0], STDIN_FILENO);
95				(void)close(pdes[0]);
96			}
97			(void)close(pdes[1]);
98		}
99		execl(_PATH_BSHELL, "sh", "-c", program, NULL);
100		_exit(127);
101		/* NOTREACHED */
102	}
103
104	/* Parent; assume fdopen can't fail. */
105	if (*type == 'r') {
106		iop = fdopen(pdes[0], type);
107		(void)close(pdes[1]);
108	} else {
109		iop = fdopen(pdes[1], type);
110		(void)close(pdes[0]);
111	}
112
113	/* Link into list of file descriptors. */
114	cur->fp = iop;
115	cur->pid =  pid;
116	cur->next = pidlist;
117	pidlist = cur;
118
119	return (iop);
120}
121
122/*
123 * pclose --
124 *	Pclose returns -1 if stream is not associated with a `popened' command,
125 *	if already `pclosed', or waitpid returns an error.
126 */
127int
128pclose(iop)
129	FILE *iop;
130{
131	register struct pid *cur, *last;
132	int omask;
133	union wait pstat;
134	pid_t pid;
135
136	(void)fclose(iop);
137
138	/* Find the appropriate file pointer. */
139	for (last = NULL, cur = pidlist; cur; last = cur, cur = cur->next)
140		if (cur->fp == iop)
141			break;
142	if (cur == NULL)
143		return (-1);
144
145	/* Get the status of the process. */
146	omask = sigblock(sigmask(SIGINT)|sigmask(SIGQUIT)|sigmask(SIGHUP));
147	do {
148		pid = waitpid(cur->pid, (int *) &pstat, 0);
149	} while (pid == -1 && errno == EINTR);
150	(void)sigsetmask(omask);
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.w_status);
160}
161