chomp: trim trailing whitespace

Attached to this email is chomp.pl, a Perl script which removes trailing whitespace from several files. I've had this for years, as trailing whitespace is one of my pet peeves.

Now that git-applymbox complains loudly whenever a patch adds trailing whitespace, I figured this script may be useful to others.

Jeff

This is the script I use for the same purpose. It's a bit more sophisticated, in that it detects and avoids binary files, and doesn't throw an error if it encounters a directory (which can happen if you give it a wildcard.)

-hpa

#!/usr/bin/perl
#
# Clean a text file of stealth whitespace
#

use bytes;

$name = 'cleanfile';

foreach $f ( @ARGV ) {
    print STDERR "$name: $f\n";

    if (! -f $f) {
	print STDERR "$f: not a file\n";
	next;
    }
    
    if (!open(FILE, '+<', $f)) {
	print STDERR "$name: Cannot open file: $f: $!\n";
	next;
    }

    binmode FILE;

    # First, verify that it is not a binary file
    $is_binary = 0;

    while (read(FILE, $data, 65536) > 0) {
	if ($data =~ /\0/) {
	    $is_binary = 1;
	    last;
	}
    }

    if ($is_binary) {
	print STDERR "$name: $f: binary file\n";
	next;
    }

    seek(FILE, 0, 0);

    @blanks = ();
    @lines  = ();

    while ( defined($line = <FILE>) ) {
	$line =~ s/[ \t\r\n]*$/\n/;

	if ( $line eq "\n" ) {
	    push(@blanks, $line);
	} else {
	    push(@lines, @blanks);
	    push(@lines, $line);
	    @blanks = ();
	}
    }

    # Any blanks at the end of the file are discarded

    seek(FILE, 0, 0);
    print FILE @lines;

    if ( !defined($where = tell(FILE)) ||
	 !truncate(FILE, $where) ) {
	die "$name: Failed to truncate modified file: $f: $!\n";
    }
    close(FILE);
}

Chewing the EOF blanks is nice. The only nit I have is that your script rewrites the file even if nothing was changed.

Jeff

Ah, good point. Attached version fixes that. It still doesn't break hard links, which may be a desirable feature.

-hpa

#!/usr/bin/perl
#
# Clean a text file of stealth whitespace
#

use bytes;

$name = 'cleanfile';

foreach $f ( @ARGV ) {
    print STDERR "$name: $f\n";

    if (! -f $f) {
	print STDERR "$f: not a file\n";
	next;
    }
    
    if (!open(FILE, '+<', $f)) {
	print STDERR "$name: Cannot open file: $f: $!\n";
	next;
    }

    binmode FILE;

    # First, verify that it is not a binary file
    $is_binary = 0;

    while (read(FILE, $data, 65536) > 0) {
	if ($data =~ /\0/) {
	    $is_binary = 1;
	    last;
	}
    }

    if ($is_binary) {
	print STDERR "$name: $f: binary file\n";
	next;
    }

    seek(FILE, 0, 0);

    $in_bytes = 0;
    $out_bytes = 0;
    $blank_bytes = 0;

    @blanks = ();
    @lines  = ();

    while ( defined($line = <FILE>) ) {
	$in_bytes += length($line);
	$line =~ s/[ \t\r\n]*$/\n/;

	if ( $line eq "\n" ) {
	    push(@blanks, $line);
	    $blank_bytes += length($line);
	} else {
	    push(@lines, @blanks);
	    $out_bytes += $blank_bytes;
	    push(@lines, $line);
	    $out_bytes += length($line);
	    @blanks = ();
	    $blank_bytes = 0;
	}
    }

    # Any blanks at the end of the file are discarded

    if ($in_bytes != $out_bytes) {
	# Only write to the file if changed
	seek(FILE, 0, 0);
	print FILE @lines;

	if ( !defined($where = tell(FILE)) ||
	     !truncate(FILE, $where) ) {
	    die "$name: Failed to truncate modified file: $f: $!\n";
	}
    }

    close(FILE);
}

Pretty long script. How about this two-liner? It does not show 'bytes chomped' but it also trims trailing whitespace.

#!/usr/bin/perl -i -p
s/[ \t\r\n]+$//

Jan Engelhardt

Hello,

perl -p -i -e 's/\s+$//' file1 file2 file3 ...

Thomas

Uhm... have either of you actually tried those? When I tried, I lose all the '\n' characters :-(

perl -pi -e 's/[ \t\r]+$//' *.[ch]

seems to actually work.

NeilBrown

Yes, it does, but a bit too aggressive for what we need :)

Jeff

trailing whitespace

And my scripts.

Whoops, should have been s/[ \t\r]+$//
And the CL form is
perl -i -pe '...'

Somehow, you can't group it to -ipe, but who cares.

Jan Engelhardt

-i takes an optional extension which is used to optionally create backup files. As such, -i must be followed by space if you want no extension (and no backup).

I love perl golf for this kind of stuff... but git-stripspace is part of git already. Even then, I tend to do it with perl -pi -e '' constructs ;-)

cheers,

m

Well, git-stripspace actually does something slightly differently, in that it also removes extraneous all-whitespace lines from the beginning, the end, and the middle (in the middle, the rule is: two or more empty lines are collapsed into one).

Ie it's a total hack for parsing just commit messages (and it is in C, because I can personally write 25 lines of C in about a millionth of the time I can write 3 lines of perl).

Linus

Hi,

But there is no good reason not to add some code and a command line switch, so that this tool with a very generic name actually performs what a normal person would expect from that name.

Ciao,
Dscho