1/*
2 * fpopen.c --- unlike the libc popen, it directly executes the
3 * command instead of call out to the shell.
4 *
5 * Copyright Theodore Ts'o, 1996-1999.
6 *
7 * Permission to use this file is granted for any purposes, as long as
8 * this copyright statement is kept intact and the author is not held
9 * liable for any damages resulting from the use of this program.
10 *
11 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
12 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
13 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
14 * WHICH ARE HEREBY DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE
15 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
16 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
17 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
18 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
19 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
20 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
21 * USE OF THIS SOFTWARE.
22 */
23
24#include <unistd.h>
25#include <stdlib.h>
26#include <stdio.h>
27#include <errno.h>
28#include <string.h>
29#include <ctype.h>
30
31#define MAX_ARGV 256
32
33extern FILE *fpopen(const char *cmd, const char *mode);
34
35FILE *fpopen(const char *cmd, const char *mode)
36{
37	char	*argv[MAX_ARGV];
38	int	i = 0;
39	char	*buf, *prog = 0;
40	char	*p;
41	int	do_stdin, do_stderr = 0;
42	int	fds[2];
43	pid_t	pid;
44
45	if (!mode) {
46		errno = EFAULT;
47		return NULL;
48	}
49
50	switch (*mode) {
51	case 'r':
52		do_stdin = 0;
53		break;
54	case 'w':
55		do_stdin = 1;
56		break;
57	default:
58		errno = EINVAL;
59		return NULL;
60	}
61	switch (*(mode+1)) {
62	case '&':
63		do_stderr = 1;
64	}
65
66	/*
67	 * Create the argv vector....
68	 */
69	buf = malloc(strlen(cmd)+1);
70	if (!buf)
71		return NULL;
72	strcpy(buf, cmd);
73	p = buf;
74	while (p && *p) {
75		if (isspace(*p)) {
76			p++;
77			continue;
78		}
79		if (i == 0)
80			prog = p;
81		argv[i++] = p;
82		p = strchr(p, ' ');
83		if (p)
84			*p++ = 0;
85	}
86
87	argv[i] = 0;
88
89	/*
90	 * Get the pipe
91	 */
92	if (pipe(fds) < 0)
93		return NULL;
94
95	/* Fork and execute the correct program. */
96	if ((pid = fork()) < 0) {
97		perror("fork");
98		return NULL;
99	} else if (pid == 0) {
100		if (do_stdin) {
101			close(fds[1]);
102			dup2(fds[0], 0);
103		} else {
104			close(fds[0]);
105			dup2(fds[1], 1);
106			if (do_stderr)
107				dup2(fds[1], 2);
108		}
109		(void) execvp(prog, argv);
110		perror(prog);
111		exit(1);
112	}
113	return fdopen(do_stdin ? fds[1] : fds[0], mode);
114}
115
116