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 }