exec.c

   1 /*
   2  * Copyright (C) 2003-2011 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
   9 #include <regex.h>
  10
  11 #include "para.h"
  12 #include "close_on_fork.h"
  13 #include "error.h"
  14 #include "fd.h"
  15 #include "string.h"
  16
  17 /**
  18  * Spawn a new process and redirect fd 0, 1, and 2.
  19  *
  20  * \param pid Will hold the pid of the created process upon return.
  21  * \param file Path of the executable to execute.
  22  * \param args The argument array for the command.
  23  * \param fds a Pointer to a value-result array.
  24  *
  25  * \return Standard.
  26  *
  27  * \sa null(4), pipe(2), dup2(2), fork(2), exec(3).
  28  */
  29 static int para_exec(pid_t *pid, const char *file, char *const *const args, int *fds)
  30 {
  31         int ret, in[2] = {-1, -1}, out[2] = {-1, -1}, err[2] = {-1, -1},
  32                 null = -1; /* ;) */
  33
  34         ret = -E_DUP_PIPE;
  35         if (fds[0] > 0 && pipe(in) < 0)
  36                 goto err_out;
  37         if (fds[1] > 0 && pipe(out) < 0)
  38                 goto err_out;
  39         if (fds[2] > 0 && pipe(err) < 0)
  40                 goto err_out;
  41         if (!fds[0] || !fds[1] || !fds[2]) {
  42                 ret = para_open("/dev/null", O_RDWR, 42);
  43                 if (ret < 0)
  44                         goto err_out;
  45                 null = ret;
  46         }
  47         ret = fork();
  48         if (ret < 0) {
  49                 ret = -ERRNO_TO_PARA_ERROR(errno);
  50                 goto err_out;
  51         }
  52         *pid = ret;
  53         if (!(*pid)) { /* child */
  54                 if (fds[0] >= 0) {
  55                         if (fds[0]) {
  56                                 close(in[1]);
  57                                 if (in[0] != STDIN_FILENO)
  58                                         dup2(in[0], STDIN_FILENO);
  59                         } else
  60                                 dup2(null, STDIN_FILENO);
  61                 }
  62                 if (fds[1] >= 0) {
  63                         if (fds[1]) {
  64                                 close(out[0]);
  65                                 if (out[1] != STDOUT_FILENO)
  66                                         dup2(out[1], STDOUT_FILENO);
  67                         } else
  68                                 dup2(null, STDOUT_FILENO);
  69                 }
  70                 if (fds[2] >= 0) {
  71                         if (fds[2]) {
  72                                 close(err[0]);
  73                                 if (err[1] != STDERR_FILENO)
  74                                         dup2(err[1], STDERR_FILENO);
  75                         } else
  76                                 dup2(null, STDERR_FILENO);
  77                 }
  78                 if (null >= 0)
  79                         close(null);
  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         if (err[0] >= 0)
 100                 close(err[0]);
 101         if (err[1] >= 0)
 102                 close(err[1]);
 103         if (out[0] >= 0)
 104                 close(out[0]);
 105         if (out[1] >= 0)
 106                 close(out[1]);
 107         if (in[0] >= 0)
 108                 close(in[0]);
 109         if (in[1] >= 0)
 110                 close(in[1]);
 111         if (null >= 0)
 112                 close(null);
 113         PARA_ERROR_LOG("%s\n", para_strerror(-ret));
 114         return ret;
 115 }
 116
 117 /**
 118  * Exec the given command.
 119  *
 120  * \param pid Will hold the pid of the created process upon return.
 121  * \param cmdline Holds the command and its arguments, seperated by spaces.
 122  * \param fds A pointer to a value-result array.
 123  *
 124  * This function uses fork/exec to create a new process. \a fds must be a
 125  * pointer to three integers, corresponding to stdin, stdout and stderr
 126  * respectively. It specifies how to deal with fd 0, 1, 2 in the child. The
 127  * contents of \a fds are interpreted as follows:
 128  *
 129  *      - fd[i] < 0: leave fd \a i alone.
 130  *      - fd[i] = 0: dup fd \a i to \p /dev/null.
 131  *      - fd[i] > 0: create a pipe and dup i to one end of that pipe.
 132  *      Upon return, fd[i] contains the file descriptor of the pipe.
 133  *
 134  *      In any case, all unneeded filedescriptors are closed.
 135  *
 136  * \return Standard.
 137  */
 138 int para_exec_cmdline_pid(pid_t *pid, const char *cmdline, int *fds)
 139 {
 140         int ret;
 141         char **argv;
 142
 143         ret = create_argv(cmdline, " \t", &argv);
 144         if (ret < 0)
 145                 return ret;
 146         ret = para_exec(pid, argv[0], argv, fds);
 147         free_argv(argv);
 148         return ret;
 149 }