ifne.c

   1
   2 /*
   3  *
   4  * Copyright 2008 Javier Merino <cibervicho@gmail.com>
   5  * This program is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License as published by the
   7  * Free Software Foundation; either version 2 of the License, or (at your
   8  * option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful, but
  11  * WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
  13  * Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  18  *
  19  */
  20
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <unistd.h>
  24 #include <sys/wait.h>
  25 #include <sys/types.h>
  26
  27 int main(int argc, char **argv) {
  28         ssize_t r;
  29         int fds[2];
  30         int child_status;
  31         pid_t child_pid;
  32         char buf[BUFSIZ];
  33
  34         if (argc < 2) {
  35                 /* Noop */
  36                 return EXIT_SUCCESS;
  37         }
  38
  39         r = read(0, buf, BUFSIZ*sizeof(char));
  40
  41         if (r == 0)
  42                 return EXIT_SUCCESS;
  43         else if (r == -1) {
  44                 perror("read");
  45                 return EXIT_FAILURE;
  46         }
  47
  48         if (pipe(fds)) {
  49                 perror("pipe");
  50                 return EXIT_FAILURE;
  51         }
  52
  53         child_pid = fork();
  54         if (!child_pid) {
  55                 /* child process: rebind stdin and exec the subcommand */
  56                 close(fds[1]);
  57                 if (dup2(fds[0], 0)) {
  58                         perror("dup2");
  59                         return EXIT_FAILURE;
  60                 }
  61
  62                 execvp(argv[1], &argv[1]);
  63                 perror(argv[1]);
  64                 close(fds[0]);
  65                 return EXIT_FAILURE;
  66         } else if (child_pid == -1) {
  67                 perror("fork");
  68                 return EXIT_FAILURE;
  69         }
  70
  71         /* Parent: write in fds[1] our stdin */
  72         close(fds[0]);
  73
  74         do {
  75                 if (write(fds[1], buf, r*sizeof(char)) == -1) {
  76                         fprintf(stderr, "Write error to %s\n", argv[1]);
  77                         exit(EXIT_FAILURE);
  78                 }
  79                 r = read(0, buf, BUFSIZ*sizeof(char));
  80         } while (r > 0);
  81         if (r == -1) {
  82                 perror("read");
  83                 exit(EXIT_FAILURE);
  84         }
  85
  86         close(fds[1]);
  87         if (waitpid(child_pid, &child_status, 0) != child_pid) {
  88                 perror("waitpid");
  89                 return EXIT_FAILURE;
  90         }
  91         if (WIFEXITED(child_status)) {
  92                 return (WEXITSTATUS(child_status));
  93         } else if (WIFSIGNALED(child_status)) {
  94                 raise(WTERMSIG(child_status));
  95                 return EXIT_FAILURE;
  96         }
  97
  98         return EXIT_FAILURE;
  99 }