exec.c

   1 /*
   2  * Copyright (C) 2003-2006 Andre Noll <maan@systemlinux.org>
   3  *
   4  *     This program is free software; you can redistribute it and/or modify
   5  *     it under the terms of the GNU General Public License as published by
   6  *     the Free Software Foundation; either version 2 of the License, or
   7  *     (at your option) any later version.
   8  *
   9  *     This program is distributed in the hope that it will be useful,
  10  *     but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  *     GNU General Public License for more details.
  13  *
  14  *     You should have received a copy of the GNU General Public License
  15  *     along with this program; if not, write to the Free Software
  16  *     Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111, USA.
  17  */
  18
  19 /** \file exec.c helper functions for spawning new processes */
  20 #include "para.h"
  21 #include "close_on_fork.h"
  22 #include "error.h"
  23 #include "string.h"
  24
  25 /**
  26  * spawn a new process and redirect fd 0, 1, and 2
  27  *
  28  * \param pid will hold the pid of the created process upon return
  29  * \param file path of the executable to execute
  30  * \param args the argument array for the command
  31  * \param fds a pointer to a value-result array
  32  *
  33  * \return Negative on errors, positive on success.
  34  *
  35  * \sa null(4), pipe(2), dup2(2), fork(2), exec(3)
  36  */
  37 static int para_exec(pid_t *pid, const char *file, char *const args[], int *fds)
  38 {
  39         int ret, in[2] = {-1, -1}, out[2] = {-1, -1}, err[2] = {-1, -1},
  40                 null = -1; /* ;) */
  41
  42         ret = -E_DUP_PIPE;
  43         if (fds[0] > 0 && pipe(in) < 0)
  44                 goto err_out;
  45         if (fds[1] > 0 && pipe(out) < 0)
  46                 goto err_out;
  47         if (fds[2] > 0 && pipe(err) < 0)
  48                 goto err_out;
  49         if (!fds[0] || !fds[1] || !fds[2]) {
  50                 ret = -E_NULL_OPEN;
  51                 null = open("/dev/null", O_RDONLY);
  52                 if (null < 0)
  53                         goto err_out;
  54         }
  55         if ((*pid = fork()) < 0)
  56                 exit(EXIT_FAILURE);
  57         if (!(*pid)) { /* child */
  58                 close_listed_fds(); /* close unneeded fds */
  59                 if (fds[0] >= 0) {
  60                         if (fds[0]) {
  61                                 close(in[1]);
  62                                 if (in[0] != STDIN_FILENO)
  63                                         dup2(in[0], STDIN_FILENO);
  64                         } else
  65                                 dup2(null, STDIN_FILENO);
  66                 }
  67                 if (fds[1] >= 0) {
  68                         if (fds[1]) {
  69                                 close(out[0]);
  70                                 if (out[1] != STDOUT_FILENO)
  71                                         dup2(out[1], STDOUT_FILENO);
  72                         } else
  73                                 dup2(null, STDOUT_FILENO);
  74                 }
  75                 if (fds[2] >= 0) {
  76                         if (fds[2]) {
  77                                 close(err[0]);
  78                                 if (err[1] != STDERR_FILENO)
  79                                         dup2(err[1], STDERR_FILENO);
  80                         } else
  81                                 dup2(null, STDERR_FILENO);
  82                 }
  83                 if (null >= 0)
  84                         close(null);
  85                 execvp(file, args);
  86                 _exit(EXIT_FAILURE);
  87         }
  88         if (fds[0] > 0) {
  89                 close(in[0]);
  90                 *fds = in[1];
  91         }
  92         if (fds[1] > 0) {
  93                 close(out[1]);
  94                 *(fds + 1) = out[0];
  95         }
  96         if (fds[2] > 0) {
  97                 close(err[1]);
  98                 *(fds + 2) = err[0];
  99         }
 100         if (null >= 0)
 101                 close(null);
 102         return 1;
 103 err_out:
 104         if (err[0] >= 0)
 105                 close(err[0]);
 106         if (err[1] >= 0)
 107                 close(err[1]);
 108         if (out[0] >= 0)
 109                 close(out[0]);
 110         if (out[1] >= 0)
 111                 close(out[1]);
 112         if (in[0] >= 0)
 113                 close(in[0]);
 114         if (in[1] >= 0)
 115                 close(in[1]);
 116         if (null >= 0)
 117                 close(null);
 118         return ret;
 119 }
 120
 121
 122 /**
 123  * exec the given command
 124  *
 125  * \param pid will hold the pid of the created process upon return
 126  * \param cmdline holds the command and its arguments, seperated by spaces
 127  * \param fds a pointer to a value-result array
 128  *
 129  * This function uses fork/exec to create a new process. \a fds must be a
 130  * pointer to three integers, corresponding to stdin, stdout and stderr
 131  * respectively. It specifies how to deal with fd 0, 1, 2 in the child. The
 132  * contents of \a fds are interpreted as follows:
 133  *
 134  *      - fd[i] < 0: leave fd \a i alone
 135  *      - fd[i] = 0: dup fd \a i to /dev/null
 136  *      - fd[i] > 0: create a pipe and dup i to one end of that pipe.
 137  *      Upon return, fd[i] contains the file descriptor of the pipe.
 138  *
 139  *      In any case, all unneeded filedescriptors are closed.
 140  *
 141  * \return positive on success, negative on errors
 142  */
 143 int para_exec_cmdline_pid(pid_t *pid, const char *cmdline, int *fds)
 144 {
 145         int argc, ret;
 146         char **argv, *tmp = para_strdup(cmdline);
 147
 148         if (!tmp)
 149                 exit(EXIT_FAILURE);
 150         argc = split_args(tmp, &argv, " \t");
 151         ret = para_exec(pid, argv[0], argv, fds);
 152         free(argv);
 153         free(tmp);
 154         return ret;
 155 }
 156