1  /*
       2   * linelength.c: find the terminal line length
       3   * Preferences: 1. MANWIDTH, 2. COLUMNS, 3. ioctl, 4. 80
       4   *
       5   * Originally adapted from Andries Brouwer's man implementation, also
       6   * released under the GPL: authors believed to include Martin Schulze and
       7   * Jon Tombs, dated 1995/09/02.
       8   *
       9   * Changes for man-db copyright (C) 2001, 2003, 2007 Colin Watson.
      10   *
      11   * This file is part of man-db.
      12   *
      13   * man-db is free software; you can redistribute it and/or modify it
      14   * under the terms of the GNU General Public License as published by
      15   * the Free Software Foundation; either version 2 of the License, or
      16   * (at your option) any later version.
      17   *
      18   * man-db is distributed in the hope that it will be useful, but
      19   * WITHOUT ANY WARRANTY; without even the implied warranty of
      20   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      21   * GNU General Public License for more details.
      22   *
      23   * You should have received a copy of the GNU General Public License
      24   * along with man-db; if not, write to the Free Software Foundation,
      25   * Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA.
      26   */
      27  
      28  #ifdef HAVE_CONFIG_H
      29  #  include "config.h"
      30  #endif /* HAVE_CONFIG_H */
      31  
      32  #include <stdlib.h>
      33  #include <stdio.h>
      34  #include <unistd.h>
      35  #include <termios.h>
      36  #include <sys/ioctl.h>
      37  #include <sys/types.h>
      38  #include <sys/stat.h>
      39  #include <fcntl.h>
      40  
      41  #include "linelength.h"
      42  
      43  #ifndef _PATH_TTY
      44  # define _PATH_TTY "/dev/tty"
      45  #endif /* _PATH_TTY */
      46  
      47  static int line_length = -1;
      48  
      49  int get_line_length (void)
      50  {
      51  	const char *columns;
      52  	int width;
      53  #ifdef TIOCGWINSZ
      54  	int dev_tty, tty_fd = -1;
      55  #endif
      56  
      57  	if (line_length != -1)
      58  		return line_length;
      59  
      60  	line_length = 80;
      61  
      62  	columns = getenv ("MANWIDTH");
      63  	if (columns != NULL) {
      64  		width = atoi (columns);
      65  		if (width > 0)
      66  			return line_length = width;
      67  	}
      68  
      69  	columns = getenv ("COLUMNS");
      70  	if (columns != NULL) {
      71  		width = atoi (columns);
      72  		if (width > 0)
      73  			return line_length = width;
      74  	}
      75  
      76  #ifdef TIOCGWINSZ
      77  	/* Original TIOCGWINSZ approach was from Jon Tombs.
      78  	 * We don't require both stdin and stdout to be a tty, and line
      79  	 * length is primarily a property of output. However, if it happens
      80  	 * that stdin is connected to a terminal but stdout isn't, then that
      81  	 * may well be because the user is trying something like
      82  	 * 'MAN_KEEP_STDERR=1 man foo >/dev/null' to see just the error
      83  	 * messages, so use the window size from stdin as a fallback.
      84  	 * In some cases we may have neither (e.g. if man is running inside
      85  	 * lesspipe); /dev/tty should be a reliable way to get to the
      86  	 * current tty if it exists.
      87  	 */
      88  	dev_tty = open (_PATH_TTY, O_RDONLY);
      89  	if (dev_tty >= 0)
      90  		tty_fd = dev_tty;
      91  	else if (isatty (STDOUT_FILENO))
      92  		tty_fd = STDOUT_FILENO;
      93  	else if (isatty (STDIN_FILENO))
      94  		tty_fd = STDIN_FILENO;
      95  	if (tty_fd >= 0) {
      96  		int ret;
      97  		struct winsize wsz;
      98  
      99  		ret = ioctl (tty_fd, TIOCGWINSZ, &wsz);
     100  		if (dev_tty >= 0)
     101  			close (dev_tty);
     102  		if (ret)
     103  			perror ("TIOCGWINSZ failed");
     104  		else if (wsz.ws_col)
     105  			return line_length = wsz.ws_col;
     106  	}
     107  #endif
     108  
     109  	return line_length = 80;
     110  }