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[dss.git] / exec.c
1 /** \file exec.c Helper functions for spawning new processes. */
2
3 #include <string.h>
4 #include <sys/types.h>
5 #include <sys/stat.h>
6 #include <fcntl.h>
7 #include <unistd.h>
8 #include <assert.h>
9 #include <stdlib.h>
10 #include <signal.h>
11
12
13 #include "gcc-compat.h"
14 #include "error.h"
15 #include "string.h"
16
17
18 /**
19 * Spawn a new process and redirect fd 0, 1, and 2.
20 *
21 * \param pid Will hold the pid of the created process upon return.
22 * \param file Path of the executable to execute.
23 * \param args The argument array for the command.
24 * \param fds a Pointer to a value-result array.
25 *
26 * \return Standard.
27 *
28 * \sa null(4), pipe(2), dup2(2), fork(2), exec(3).
29 */
30 int dss_exec(pid_t *pid, const char *file, char *const *const args, int *fds)
31 {
32 int ret, in[2] = {-1, -1}, out[2] = {-1, -1}, err[2] = {-1, -1},
33 null = -1; /* ;) */
34
35 ret = -E_DUP_PIPE;
36 if (fds[0] > 0 && pipe(in) < 0)
37 goto err_out;
38 if (fds[1] > 0 && pipe(out) < 0)
39 goto err_out;
40 if (fds[2] > 0 && pipe(err) < 0)
41 goto err_out;
42 if (!fds[0] || !fds[1] || !fds[2]) {
43 ret = -E_NULL_OPEN;
44 null = open("/dev/null", O_RDONLY);
45 if (null < 0)
46 goto err_out;
47 }
48 if ((*pid = fork()) < 0)
49 exit(EXIT_FAILURE);
50 if (!(*pid)) { /* child */
51 if (fds[0] >= 0) {
52 if (fds[0]) {
53 close(in[1]);
54 if (in[0] != STDIN_FILENO)
55 dup2(in[0], STDIN_FILENO);
56 } else
57 dup2(null, STDIN_FILENO);
58 }
59 if (fds[1] >= 0) {
60 if (fds[1]) {
61 close(out[0]);
62 if (out[1] != STDOUT_FILENO)
63 dup2(out[1], STDOUT_FILENO);
64 } else
65 dup2(null, STDOUT_FILENO);
66 }
67 if (fds[2] >= 0) {
68 if (fds[2]) {
69 close(err[0]);
70 if (err[1] != STDERR_FILENO)
71 dup2(err[1], STDERR_FILENO);
72 } else
73 dup2(null, STDERR_FILENO);
74 }
75 if (null >= 0)
76 close(null);
77 signal(SIGINT, SIG_DFL);
78 signal(SIGTERM, SIG_DFL);
79 signal(SIGCHLD, SIG_DFL);
80 execvp(file, args);
81 _exit(EXIT_FAILURE);
82 }
83 if (fds[0] > 0) {
84 close(in[0]);
85 *fds = in[1];
86 }
87 if (fds[1] > 0) {
88 close(out[1]);
89 *(fds + 1) = out[0];
90 }
91 if (fds[2] > 0) {
92 close(err[1]);
93 *(fds + 2) = err[0];
94 }
95 if (null >= 0)
96 close(null);
97 return 1;
98 err_out:
99 make_err_msg("failed to exec %s", file);
100 if (err[0] >= 0)
101 close(err[0]);
102 if (err[1] >= 0)
103 close(err[1]);
104 if (out[0] >= 0)
105 close(out[0]);
106 if (out[1] >= 0)
107 close(out[1]);
108 if (in[0] >= 0)
109 close(in[0]);
110 if (in[1] >= 0)
111 close(in[1]);
112 if (null >= 0)
113 close(null);
114 return ret;
115 }
116
117
118 /**
119 * Exec the given command.
120 *
121 * \param pid Will hold the pid of the created process upon return.
122 * \param cmdline Holds the command and its arguments, seperated by spaces.
123 * \param fds A pointer to a value-result array.
124 *
125 * This function uses fork/exec to create a new process. \a fds must be a
126 * pointer to three integers, corresponding to stdin, stdout and stderr
127 * respectively. It specifies how to deal with fd 0, 1, 2 in the child. The
128 * contents of \a fds are interpreted as follows:
129 *
130 * - fd[i] < 0: leave fd \a i alone.
131 * - fd[i] = 0: dup fd \a i to \p /dev/null.
132 * - fd[i] > 0: create a pipe and dup i to one end of that pipe.
133 * Upon return, fd[i] contains the file descriptor of the pipe.
134 *
135 * In any case, all unneeded filedescriptors are closed.
136 *
137 * \return Standard.
138 */
139 int dss_exec_cmdline_pid(pid_t *pid, const char *cmdline, int *fds)
140 {
141 int argc, ret;
142 char **argv;
143 char *tmp = dss_strdup(cmdline);
144
145 if (!tmp)
146 exit(EXIT_FAILURE);
147 argc = split_args(tmp, &argv, " \t");
148 ret = dss_exec(pid, argv[0], argv, fds);
149 free(argv);
150 free(tmp);
151 return ret;
152 }
153
154