popen.c revision 3884bfe9661955543ce203c60f9225bbdf33f6bb 
1/*	$OpenBSD: popen.c,v 1.17 2005/08/08 08:05:34 espie Exp $ */
2/*
3 * Copyright (c) 1988, 1993
4 *	The Regents of the University of California.  All rights reserved.
5 *
6 * This code is derived from software written by Ken Arnold and
7 * published in UNIX Review, Vol. 6, No. 8.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 *    notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 *    notice, this list of conditions and the following disclaimer in the
16 *    documentation and/or other materials provided with the distribution.
17 * 3. Neither the name of the University nor the names of its contributors
18 *    may be used to endorse or promote products derived from this software
19 *    without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34#include <sys/param.h>
35#include <sys/wait.h>
36
37#include <signal.h>
38#include <errno.h>
39#include <unistd.h>
40#include <stdio.h>
41#include <stdlib.h>
42#include <string.h>
43#include <paths.h>
44
45static struct pid {
46	struct pid *next;
47	FILE *fp;
48	pid_t pid;
49} *pidlist;
50
51extern char **environ;
52
53FILE *
54popen(const char *program, const char *type)
55{
56	struct pid * volatile cur;
57	FILE *iop;
58	int pdes[2];
59	pid_t pid;
60	char *argp[] = {"sh", "-c", NULL, NULL};
61
62	if ((*type != 'r' && *type != 'w') || type[1] != '\0') {
63		errno = EINVAL;
64		return (NULL);
65	}
66
67	if ((cur = malloc(sizeof(struct pid))) == NULL)
68		return (NULL);
69
70	if (pipe(pdes) < 0) {
71		free(cur);
72		return (NULL);
73	}
74
75	switch (pid = fork()) {
76	case -1:			/* Error. */
77		(void)close(pdes[0]);
78		(void)close(pdes[1]);
79		free(cur);
80		return (NULL);
81		/* NOTREACHED */
82	case 0:				/* Child. */
83	    {
84		struct pid *pcur;
85		/*
86		 * We fork()'d, we got our own copy of the list, no
87		 * contention.
88		 */
89		for (pcur = pidlist; pcur; pcur = pcur->next)
90			close(fileno(pcur->fp));
91
92		if (*type == 'r') {
93			(void) close(pdes[0]);
94			if (pdes[1] != STDOUT_FILENO) {
95				(void)dup2(pdes[1], STDOUT_FILENO);
96				(void)close(pdes[1]);
97			}
98		} else {
99			(void)close(pdes[1]);
100			if (pdes[0] != STDIN_FILENO) {
101				(void)dup2(pdes[0], STDIN_FILENO);
102				(void)close(pdes[0]);
103			}
104		}
105		argp[2] = (char *)program;
106		execve(_PATH_BSHELL, argp, environ);
107		_exit(127);
108		/* NOTREACHED */
109	    }
110	}
111
112	/* Parent; assume fdopen can't fail. */
113	if (*type == 'r') {
114		iop = fdopen(pdes[0], type);
115		(void)close(pdes[1]);
116	} else {
117		iop = fdopen(pdes[1], type);
118		(void)close(pdes[0]);
119	}
120
121	/* Link into list of file descriptors. */
122	cur->fp = iop;
123	cur->pid =  pid;
124	cur->next = pidlist;
125	pidlist = cur;
126
127	return (iop);
128}
129
130/*
131 * pclose --
132 *	Pclose returns -1 if stream is not associated with a `popened' command,
133 *	if already `pclosed', or waitpid returns an error.
134 */
135int
136pclose(FILE *iop)
137{
138	struct pid *cur, *last;
139	int pstat;
140	pid_t pid;
141
142	/* Find the appropriate file pointer. */
143	for (last = NULL, cur = pidlist; cur; last = cur, cur = cur->next)
144		if (cur->fp == iop)
145			break;
146
147	if (cur == NULL)
148		return (-1);
149
150	(void)fclose(iop);
151
152	do {
153		pid = waitpid(cur->pid, &pstat, 0);
154	} while (pid == -1 && errno == EINTR);
155
156	/* Remove the entry from the linked list. */
157	if (last == NULL)
158		pidlist = cur->next;
159	else
160		last->next = cur->next;
161	free(cur);
162
163	return (pid == -1 ? -1 : pstat);
164}
165