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 #include "m_popen.h"
  12
  13 static  int m_pid = NOTOK;      /* Process we're waiting for */
  14 static  int sd = NOTOK;         /* Original standard output */
  15
  16 /*
  17  * Fork a process and redirect our standard output to that process
  18  */
  19
  20 void
  21 m_popen (char *name, int savestdout)
  22 {
  23     int pd[2];
  24     char *file;
  25     char **arglist;
  26
  27     if (savestdout && (sd = dup (fileno (stdout))) == NOTOK)
  28         adios ("standard output", "unable to dup()");
  29
  30     if (pipe (pd) == NOTOK)
  31         adios ("pipe", "unable to");
  32
  33     switch (m_pid = fork()) {
  34         case NOTOK:
  35             adios ("fork", "unable to");
  36
  37         case OK:
  38             SIGNAL (SIGINT, SIG_DFL);
  39             SIGNAL (SIGQUIT, SIG_DFL);
  40
  41             close (pd[1]);
  42             if (pd[0] != fileno (stdin)) {
  43                 dup2 (pd[0], fileno (stdin));
  44                 close (pd[0]);
  45             }
  46             arglist = argsplit(name, &file, NULL);
  47             execvp (file, arglist);
  48             fprintf (stderr, "unable to exec ");
  49             perror (name);
  50             _exit(1);
  51
  52         default:
  53             close (pd[0]);
  54             if (pd[1] != fileno (stdout)) {
  55                 dup2 (pd[1], fileno (stdout));
  56                 close (pd[1]);
  57             }
  58     }
  59 }
  60
  61
  62 void
  63 m_pclose (void)
  64 {
  65     if (m_pid == NOTOK)
  66         return;
  67
  68     if (sd != NOTOK) {
  69         fflush (stdout);
  70         if (dup2 (sd, fileno (stdout)) == NOTOK)
  71             adios ("standard output", "unable to dup2()");
  72
  73         clearerr (stdout);
  74         close (sd);
  75         sd = NOTOK;
  76     }
  77     else
  78         fclose (stdout);
  79
  80     pidwait (m_pid, OK);
  81     m_pid = NOTOK;
  82 }