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
   9 #include <regex.h>
  10 #include <dirent.h>
  11
  12 #include "para.h"
  13 #include "close_on_fork.h"
  14 #include "error.h"
  15 #include "fd.h"
  16 #include "string.h"
  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 static int para_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 = para_open("/dev/null", O_RDWR, 42);
  44                 if (ret < 0)
  45                         goto err_out;
  46                 null = ret;
  47         }
  48         ret = fork();
  49         if (ret < 0) {
  50                 ret = -ERRNO_TO_PARA_ERROR(errno);
  51                 goto err_out;
  52         }
  53         *pid = ret;
  54         if (!(*pid)) { /* child */
  55                 if (fds[0] >= 0) {
  56                         if (fds[0]) {
  57                                 close(in[1]);
  58                                 if (in[0] != STDIN_FILENO)
  59                                         dup2(in[0], STDIN_FILENO);
  60                         } else
  61                                 dup2(null, STDIN_FILENO);
  62                 }
  63                 if (fds[1] >= 0) {
  64                         if (fds[1]) {
  65                                 close(out[0]);
  66                                 if (out[1] != STDOUT_FILENO)
  67                                         dup2(out[1], STDOUT_FILENO);
  68                         } else
  69                                 dup2(null, STDOUT_FILENO);
  70                 }
  71                 if (fds[2] >= 0) {
  72                         if (fds[2]) {
  73                                 close(err[0]);
  74                                 if (err[1] != STDERR_FILENO)
  75                                         dup2(err[1], STDERR_FILENO);
  76                         } else
  77                                 dup2(null, STDERR_FILENO);
  78                 }
  79                 if (null >= 0)
  80                         close(null);
  81                 execvp(file, args);
  82                 _exit(EXIT_FAILURE);
  83         }
  84         if (fds[0] > 0) {
  85                 close(in[0]);
  86                 *fds = in[1];
  87         }
  88         if (fds[1] > 0) {
  89                 close(out[1]);
  90                 *(fds + 1) = out[0];
  91         }
  92         if (fds[2] > 0) {
  93                 close(err[1]);
  94                 *(fds + 2) = err[0];
  95         }
  96         if (null >= 0)
  97                 close(null);
  98         return 1;
  99 err_out:
 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         PARA_ERROR_LOG("%s\n", para_strerror(-ret));
 115         return ret;
 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 para_exec_cmdline_pid(pid_t *pid, const char *cmdline, int *fds)
 140 {
 141         int ret;
 142         char **argv;
 143
 144         ret = create_argv(cmdline, " \t", &argv);
 145         if (ret < 0)
 146                 return ret;
 147         ret = para_exec(pid, argv[0], argv, fds);
 148         free_argv(argv);
 149         return ret;
 150 }