ifne.c

   1 /*
   2  *
   3  * Copyright 2008 Javier Merino <cibervicho@gmail.com>
   4  * This program is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU General Public License as published by the
   6  * Free Software Foundation; either version 2 of the License, or (at your
   7  * option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
  12  * Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License along
  15  * with this program; if not, write to the Free Software Foundation, Inc.,
  16  * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  17  *
  18  */
  19
  20 #include <stdio.h>
  21 #include <stdlib.h>
  22 #include <unistd.h>
  23 #include <sys/wait.h>
  24 #include <sys/types.h>
  25
  26 int main(int argc, char **argv) {
  27         ssize_t r;
  28         int fds[2];
  29         int child_status;
  30         pid_t child_pid;
  31         char buf[BUFSIZ];
  32         FILE *outf;
  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 stdin to fds[1] */
  72         close(fds[0]);
  73         outf = fdopen(fds[1], "w");
  74         if (! outf) {
  75                 perror("fdopen");
  76                 exit(1);
  77         }
  78         do {
  79                 if (fwrite(buf, r*sizeof(char), 1, outf) < 1) {
  80                         fprintf(stderr, "Write error to %s\n", argv[1]);
  81                         exit(EXIT_FAILURE);
  82                 }
  83                 r = read(0, buf, BUFSIZ*sizeof(char));
  84         } while (r > 0);
  85         if (r == -1) {
  86                 perror("read");
  87                 exit(EXIT_FAILURE);
  88         }
  89         fclose(outf);
  90
  91         if (waitpid(child_pid, &child_status, 0) != child_pid) {
  92                 perror("waitpid");
  93                 return EXIT_FAILURE;
  94         }
  95         if (WIFEXITED(child_status)) {
  96                 return (WEXITSTATUS(child_status));
  97         } else if (WIFSIGNALED(child_status)) {
  98                 raise(WTERMSIG(child_status));
  99                 return EXIT_FAILURE;
 100         }
 101
 102         return EXIT_FAILURE;
 103 }