highlight stderr in bash

hilite.c

/*
 * hilite - runs a command, highlighting everything it sends to stderr
 * version 1.5
 *
 * Copyright (C) 2000, 2001  Mike Schiraldi <mgs21@columbia.edu>
 *
 * See www.sf.net/forum/forum.php?forum_id=104071 for news and info
 *
 * Or just www.sf.net/projects/hilite if the above link is no good
 *
 */

/*
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program, but Mike's a lazy bastard. To get one,
 * write to the Free Software Foundation, Inc., 59 Temple Place - Suite
 * 330, Boston, MA 02111-1307, USA.
 */

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/wait.h>

#define HEADER "\033[91m"
#define FOOTER "\033[0m"

#define FAIL(msg) { fprintf (stderr, "%s: " msg "() failed: %s\n", argv[0], \
                              strerror (errno)); return 1; }

int
main (int argc, char **argv)
{
  int p[2];
  int f;

  if (argc < 2)
    {
      fprintf (stderr, "%s: specify a command to execute\n", argv[0]);
      return 1;
    }

  if (pipe (p) != 0)
    FAIL ("pipe");

  f = fork ();

  if (f == -1)
    FAIL ("fork");

  if (f)
    {
      int status;

      close (p[1]);

    again:
      errno = 0;

      while (1) 
        {
          int r;
          char buf[BUFSIZ];

	  r = read (p[0], buf, BUFSIZ - 1);

	  if (r <= 0)
            break;

          buf[r] = 0;
          fprintf (stderr, "%s%s%s", HEADER, buf, FOOTER);
	}

      if (errno == EINTR) 
        {
          fprintf (stderr, "%s: read interrupted, trying again\n", argv[0]);
          goto again;
        }

      if (errno != 0) 
          FAIL ("read");

      if (wait (&status) != f)
          FAIL ("wait");
      
      return WEXITSTATUS (status);
    }
  else
    {
      int fd;

      close (p[0]);
      close (fileno (stderr));

      fd = dup (p[1]); /* dup() uses the lowest available fd, which should be stderr's 
                        * since we just closed it */

      /* Can't use stderr for these problems, since we just closed it */
      if (fd < 0)
	{
	  printf ("%s: dup() failed: %s\n", argv[0], strerror (errno));
	  return 1;
	}

      if (fd != fileno (stderr))
        {
	  printf ("%s: dup returned %d instead of %d\n", argv[0], fd, 
                  fileno (stderr));
          return 1;
        }

      execvp (argv[1], &argv[1]);

      FAIL ("exec");
    }
}