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

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