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[paraslash.git] / exec.c
1 /*
2 * Copyright (C) 2003-2006 Andre Noll <maan@systemlinux.org>
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111, USA.
17 */
18
19 /** \file exec.c helper functions for spawning new processes */
20 #include "para.h"
21 #include "close_on_fork.h"
22 #include "error.h"
23 #include "string.h"
24
25 /**
26 * spawn a new process and redirect fd 0, 1, and 2
27 *
28 * \param pid will hold the pid of the created process upon return
29 * \param file path of the executable to execute
30 * \param args the argument array for the command
31 * \param fds a pointer to a value-result array
32 *
33 * This function uses fork/exec to create a new process. \a fds must be a
34 * pointer to three integers, corresponding to stdin, stdout and stderr
35 * respectively. It specifies how to deal with fd 0, 1, 2 in the child. The
36 * contents of \a fds are interpreted as follows:
37 *
38 * - fd[i] < 0: leave fd \a i alone
39 * - fd[i] = 0: dup fd \a i to /dev/null
40 * - fd[i] > 0: create a pipe and dup i to one end of that pipe.
41 * Upon return, fd[i] contains the file descriptor of the pipe.
42 *
43 * In any case, all unneeded filedescriptors are closed.
44 *
45 * \return Negative on errors, positive on success.
46 *
47 * \sa null(4), pipe(2), dup2(2), fork(2), exec(3)
48 */
49 int para_exec(pid_t *pid, const char *file, char *const args[], int *fds)
50 {
51 int ret, in[2] = {-1, -1}, out[2] = {-1, -1}, err[2] = {-1, -1},
52 null = -1; /* ;) */
53
54 ret = -E_DUP_PIPE;
55 if (fds[0] > 0 && pipe(in) < 0)
56 goto err_out;
57 if (fds[1] > 0 && pipe(out) < 0)
58 goto err_out;
59 if (fds[2] > 0 && pipe(err) < 0)
60 goto err_out;
61 if (!fds[0] || !fds[1] || !fds[2]) {
62 ret = -E_NULL_OPEN;
63 null = open("/dev/null", O_RDONLY);
64 if (null < 0)
65 goto err_out;
66 }
67 if ((*pid = fork()) < 0)
68 exit(EXIT_FAILURE);
69 if (!(*pid)) { /* child */
70 close_listed_fds(); /* close unneeded fds */
71 if (fds[0] >= 0) {
72 if (fds[0]) {
73 close(in[1]);
74 if (in[0] != STDIN_FILENO)
75 dup2(in[0], STDIN_FILENO);
76 } else
77 dup2(null, STDIN_FILENO);
78 }
79 if (fds[1] >= 0) {
80 if (fds[1]) {
81 close(out[0]);
82 if (out[1] != STDOUT_FILENO)
83 dup2(out[1], STDOUT_FILENO);
84 } else
85 dup2(null, STDOUT_FILENO);
86 }
87 if (fds[2] >= 0) {
88 if (fds[2]) {
89 close(err[0]);
90 if (err[1] != STDERR_FILENO)
91 dup2(err[1], STDERR_FILENO);
92 } else
93 dup2(null, STDERR_FILENO);
94 }
95 if (null >= 0)
96 close(null);
97 execvp(file, args);
98 _exit(EXIT_FAILURE);
99 }
100 if (fds[0] > 0) {
101 close(in[0]);
102 *fds = in[1];
103 }
104 if (fds[1] > 0) {
105 close(out[1]);
106 *(fds + 1) = out[0];
107 }
108 if (fds[2] > 0) {
109 close(err[1]);
110 *(fds + 2) = err[0];
111 }
112 if (null >= 0)
113 close(null);
114 return 1;
115 err_out:
116 if (err[0] >= 0)
117 close(err[0]);
118 if (err[1] >= 0)
119 close(err[1]);
120 if (out[0] >= 0)
121 close(out[0]);
122 if (out[1] >= 0)
123 close(out[1]);
124 if (in[0] >= 0)
125 close(in[0]);
126 if (in[1] >= 0)
127 close(in[1]);
128 if (null >= 0)
129 close(null);
130 return ret;
131 }
132
133
134 /**
135 * exec the given command
136 *
137 * \param pid the same meaning as in para_exec()
138 * \param cmdline holds the command and its arguments, seperated by spaces
139 * \param fds the same meaning as in para_exec()
140 *
141 * A wrapper for para_exec() which calls split_args() to seperate
142 * the command line arguments.
143 *
144 * \return positive on success, negative on errors
145 */
146 int para_exec_cmdline_pid(pid_t *pid, char *cmdline, int *fds)
147 {
148 int argc, ret;
149 char **argv, *tmp = para_strdup(cmdline);
150
151 if (!tmp)
152 exit(EXIT_FAILURE);
153 argc = split_args(tmp, &argv, ' ');
154 ret = para_exec(pid, argv[0], argv, fds);
155 free(argv);
156 free(tmp);
157 return ret;
158 }
159
160 /**
161 * check whether a file exists
162 *
163 * \param fn the file name
164 *
165 * \return Non-zero iff file exists.
166 */
167 int file_exists(const char *fn)
168 {
169 struct stat statbuf;
170
171 return !stat(fn, &statbuf);
172 }