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 "config.h"
25 #include <unistd.h>
26 #include <stdlib.h>
27 #include <stdio.h>
28 #include <errno.h>
29 #include <string.h>
30 #include <ctype.h>
31 
32 #define MAX_ARGV 256
33 
34 extern FILE *fpopen(const char *cmd, const char *mode);
35 
36 FILE *fpopen(const char *cmd, const char *mode)
37 {
38 	char	*argv[MAX_ARGV];
39 	int	i = 0;
40 	char	*buf, *prog = 0;
41 	char	*p;
42 	int	do_stdin, do_stderr = 0;
43 	int	fds[2];
44 	pid_t	pid;
45 
46 	if (!mode) {
47 		errno = EFAULT;
48 		return NULL;
49 	}
50 
51 	switch (*mode) {
52 	case 'r':
53 		do_stdin = 0;
54 		break;
55 	case 'w':
56 		do_stdin = 1;
57 		break;
58 	default:
59 		errno = EINVAL;
60 		return NULL;
61 	}
62 	switch (*(mode+1)) {
63 	case '&':
64 		do_stderr = 1;
65 	}
66 
67 	/*
68 	 * Create the argv vector....
69 	 */
70 	buf = malloc(strlen(cmd)+1);
71 	if (!buf)
72 		return NULL;
73 	strcpy(buf, cmd);
74 	p = buf;
75 	while (p && *p) {
76 		if (isspace(*p)) {
77 			p++;
78 			continue;
79 		}
80 		if (i == 0)
81 			prog = p;
82 		argv[i++] = p;
83 		p = strchr(p, ' ');
84 		if (p)
85 			*p++ = 0;
86 	}
87 
88 	argv[i] = 0;
89 
90 	/*
91 	 * Get the pipe
92 	 */
93 	if (pipe(fds) < 0)
94 		return NULL;
95 
96 	/* Fork and execute the correct program. */
97 	if ((pid = fork()) < 0) {
98 		perror("fork");
99 		return NULL;
100 	} else if (pid == 0) {
101 		if (do_stdin) {
102 			close(fds[1]);
103 			dup2(fds[0], 0);
104 		} else {
105 			close(fds[0]);
106 			dup2(fds[1], 1);
107 			if (do_stderr)
108 				dup2(fds[1], 2);
109 		}
110 		(void) execvp(prog, argv);
111 		perror(prog);
112 		exit(1);
113 	}
114 	return fdopen(do_stdin ? fds[1] : fds[0], mode);
115 }
116 
117