86a483cfd8e704eda8907d7399e891f603633393
[paraslash.git] / exec.c
1 /*
2 * Copyright (C) 2003-2009 Andre Noll <maan@systemlinux.org>
3 *
4 * Licensed under the GPL v2. For licencing details see COPYING.
5 */
6
7 /** \file exec.c Helper functions for spawning new processes. */
8 #include <dirent.h>
9 #include "para.h"
10 #include "close_on_fork.h"
11 #include "error.h"
12 #include "string.h"
13 #include "fd.h"
14
15 /**
16 * Spawn a new process and redirect fd 0, 1, and 2.
17 *
18 * \param pid Will hold the pid of the created process upon return.
19 * \param file Path of the executable to execute.
20 * \param args The argument array for the command.
21 * \param fds a Pointer to a value-result array.
22 *
23 * \return Standard.
24 *
25 * \sa null(4), pipe(2), dup2(2), fork(2), exec(3).
26 */
27 static int para_exec(pid_t *pid, const char *file, char *const *const args, int *fds)
28 {
29 int ret, in[2] = {-1, -1}, out[2] = {-1, -1}, err[2] = {-1, -1},
30 null = -1; /* ;) */
31
32 ret = -E_DUP_PIPE;
33 if (fds[0] > 0 && pipe(in) < 0)
34 goto err_out;
35 if (fds[1] > 0 && pipe(out) < 0)
36 goto err_out;
37 if (fds[2] > 0 && pipe(err) < 0)
38 goto err_out;
39 if (!fds[0] || !fds[1] || !fds[2]) {
40 ret = para_open("/dev/null", O_RDWR, 42);
41 if (ret < 0)
42 goto err_out;
43 null = ret;
44 }
45 ret = fork();
46 if (ret < 0) {
47 ret = -ERRNO_TO_PARA_ERROR(errno);
48 goto err_out;
49 }
50 *pid = ret;
51 if (!(*pid)) { /* child */
52 if (fds[0] >= 0) {
53 if (fds[0]) {
54 close(in[1]);
55 if (in[0] != STDIN_FILENO)
56 dup2(in[0], STDIN_FILENO);
57 } else
58 dup2(null, STDIN_FILENO);
59 }
60 if (fds[1] >= 0) {
61 if (fds[1]) {
62 close(out[0]);
63 if (out[1] != STDOUT_FILENO)
64 dup2(out[1], STDOUT_FILENO);
65 } else
66 dup2(null, STDOUT_FILENO);
67 }
68 if (fds[2] >= 0) {
69 if (fds[2]) {
70 close(err[0]);
71 if (err[1] != STDERR_FILENO)
72 dup2(err[1], STDERR_FILENO);
73 } else
74 dup2(null, STDERR_FILENO);
75 }
76 if (null >= 0)
77 close(null);
78 execvp(file, args);
79 _exit(EXIT_FAILURE);
80 }
81 if (fds[0] > 0) {
82 close(in[0]);
83 *fds = in[1];
84 }
85 if (fds[1] > 0) {
86 close(out[1]);
87 *(fds + 1) = out[0];
88 }
89 if (fds[2] > 0) {
90 close(err[1]);
91 *(fds + 2) = err[0];
92 }
93 if (null >= 0)
94 close(null);
95 return 1;
96 err_out:
97 if (err[0] >= 0)
98 close(err[0]);
99 if (err[1] >= 0)
100 close(err[1]);
101 if (out[0] >= 0)
102 close(out[0]);
103 if (out[1] >= 0)
104 close(out[1]);
105 if (in[0] >= 0)
106 close(in[0]);
107 if (in[1] >= 0)
108 close(in[1]);
109 if (null >= 0)
110 close(null);
111 PARA_ERROR_LOG("%s\n", para_strerror(-ret));
112 return ret;
113 }
114
115 /**
116 * Exec the given command.
117 *
118 * \param pid Will hold the pid of the created process upon return.
119 * \param cmdline Holds the command and its arguments, seperated by spaces.
120 * \param fds A pointer to a value-result array.
121 *
122 * This function uses fork/exec to create a new process. \a fds must be a
123 * pointer to three integers, corresponding to stdin, stdout and stderr
124 * respectively. It specifies how to deal with fd 0, 1, 2 in the child. The
125 * contents of \a fds are interpreted as follows:
126 *
127 * - fd[i] < 0: leave fd \a i alone.
128 * - fd[i] = 0: dup fd \a i to \p /dev/null.
129 * - fd[i] > 0: create a pipe and dup i to one end of that pipe.
130 * Upon return, fd[i] contains the file descriptor of the pipe.
131 *
132 * In any case, all unneeded filedescriptors are closed.
133 *
134 * \return Standard.
135 */
136 int para_exec_cmdline_pid(pid_t *pid, const char *cmdline, int *fds)
137 {
138 int ret;
139 char **argv;
140 char *tmp = para_strdup(cmdline);
141
142 split_args(tmp, &argv, " \t");
143 ret = para_exec(pid, argv[0], argv, fds);
144 free(argv);
145 free(tmp);
146 return ret;
147 }