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 "arglist.h"
  11 #include "error.h"
  12 #include "h/signals.h"
  13 #include "m_popen.h"
  14
  15 static  int m_pid = NOTOK;      /* Process we're waiting for */
  16 static  int sd = NOTOK;         /* Original standard output */
  17
  18 /*
  19  * Fork a process and redirect our standard output to that process
  20  */
  21
  22 void
  23 m_popen (char *name, int savestdout)
  24 {
  25     int pd[2];
  26     char *file;
  27     char **arglist;
  28
  29     if (savestdout && (sd = dup (fileno (stdout))) == NOTOK)
  30         adios ("standard output", "unable to dup()");
  31
  32     if (pipe (pd) == NOTOK)
  33         adios ("pipe", "unable to");
  34
  35     switch (m_pid = fork()) {
  36         case NOTOK:
  37             adios ("fork", "unable to");
  38
  39         case OK:
  40             SIGNAL (SIGINT, SIG_DFL);
  41             SIGNAL (SIGQUIT, SIG_DFL);
  42
  43             close (pd[1]);
  44             if (pd[0] != fileno (stdin)) {
  45                 dup2 (pd[0], fileno (stdin));
  46                 close (pd[0]);
  47             }
  48             arglist = argsplit(name, &file, NULL);
  49             execvp (file, arglist);
  50             fprintf (stderr, "unable to exec ");
  51             perror (name);
  52             _exit(1);
  53
  54         default:
  55             close (pd[0]);
  56             if (pd[1] != fileno (stdout)) {
  57                 dup2 (pd[1], fileno (stdout));
  58                 close (pd[1]);
  59             }
  60     }
  61 }
  62
  63
  64 void
  65 m_pclose (void)
  66 {
  67     if (m_pid == NOTOK)
  68         return;
  69
  70     if (sd != NOTOK) {
  71         fflush (stdout);
  72         if (dup2 (sd, fileno (stdout)) == NOTOK)
  73             adios ("standard output", "unable to dup2()");
  74
  75         clearerr (stdout);
  76         close (sd);
  77         sd = NOTOK;
  78     }
  79     else
  80         fclose (stdout);
  81
  82     pidwait (m_pid, OK);
  83     m_pid = NOTOK;
  84 }