diplodocus.org Git - nmh/blob - sbr/m_popen.c

   1
   2 /*
   3  * m_popen.c -- Interface for a popen() call that redirects the current
   4  *              process standard output to the popen()d process.
   5  *
   6  * This code is Copyright (c) 2014, by the authors of nmh.  See the
   7  * COPYRIGHT file in the root directory of the nmh distribution for
   8  * complete copyright information.
   9  */
  10
  11 #include <h/mh.h>
  12 #include <h/signals.h>
  13
  14 static  int m_pid = NOTOK;      /* Process we're waiting for */
  15 static  int sd = NOTOK;         /* Original standard output */
  16
  17 /*
  18  * Fork a process and redirect our standard output to that process
  19  */
  20
  21 void
  22 m_popen (char *name, int savestdout)
  23 {
  24     int pd[2];
  25     char *file;
  26     char **arglist;
  27
  28     if (savestdout && (sd = dup (fileno (stdout))) == NOTOK)
  29         adios ("standard output", "unable to dup()");
  30
  31     if (pipe (pd) == NOTOK)
  32         adios ("pipe", "unable to");
  33
  34     switch (m_pid = fork()) {
  35         case NOTOK:
  36             adios ("fork", "unable to");
  37
  38         case OK:
  39             SIGNAL (SIGINT, SIG_DFL);
  40             SIGNAL (SIGQUIT, SIG_DFL);
  41
  42             close (pd[1]);
  43             if (pd[0] != fileno (stdin)) {
  44                 dup2 (pd[0], fileno (stdin));
  45                 close (pd[0]);
  46             }
  47             arglist = argsplit(name, &file, NULL);
  48             execvp (file, arglist);
  49             fprintf (stderr, "unable to exec ");
  50             perror (name);
  51             _exit (-1);
  52
  53         default:
  54             close (pd[0]);
  55             if (pd[1] != fileno (stdout)) {
  56                 dup2 (pd[1], fileno (stdout));
  57                 close (pd[1]);
  58             }
  59     }
  60 }
  61
  62
  63 void
  64 m_pclose (void)
  65 {
  66     if (m_pid == NOTOK)
  67         return;
  68
  69     if (sd != NOTOK) {
  70         fflush (stdout);
  71         if (dup2 (sd, fileno (stdout)) == NOTOK)
  72             adios ("standard output", "unable to dup2()");
  73
  74         clearerr (stdout);
  75         close (sd);
  76         sd = NOTOK;
  77     }
  78     else
  79         fclose (stdout);
  80
  81     pidwait (m_pid, OK);
  82     m_pid = NOTOK;
  83 }