mph151 has asked for the wisdom of the Perl Monks concerning the following question:

I am old school, I have a DOS batch that copies a file created by another app from one location and drops it in another. The app adds a CR and an LF at the end of the text file. I need to remove the last CR and LF. The file transfer runs every night and the data size will vary. I know Perl could do this but I an to much of a novice with Perl. Can the good monks help me? Mike

Replies are listed 'Best First'.
Re: delete last CR and LF from txt
by roboticus (Chancellor) on Feb 22, 2010 at 18:08 UTC

    mph151:

    Perhaps the simplest way is to:

    1. Open the file
    2. Seek to two byes before the end of the file
    3. Truncate the file
    4. close the file

    Note: the first word of each line is the name of the perl function that does the job.

    ...roboticus

[reply]
Re: delete last CR and LF from txt
by ikegami (Patriarch) on Feb 22, 2010 at 18:19 UTC
    The following will remove all trailing empty lines. 
    perl -i.bak -nle"while ($empty) { --$empty; print '' } if (length()) {
+ print } else { ++$empty }" filename

    [download]

    For example, 

    foo CR LF
bar CR LF
CR LF
CR LF

    [download]
    will become 
    foo CR LF
bar CR LF

    [download]
[reply]
[d/l]
[select]
Re: delete last CR and LF from txt
by BrowserUk (Patriarch) on Feb 22, 2010 at 19:28 UTC

    If you know the crlf will always be there: 

    perl -E"$s=-s $ARGV[ 0 ]; truncate( $ARGV[0], $s-2 ) or die $!" junk.d
+at

    [download]
    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
    "Science is about questioning the status quo. Questioning authority".
    In the absence of evidence, opinion is indistinguishable from prejudice.
[reply]
[d/l]
      Even if you dont know its there you can seek to the last 2 bytes and read them and compare them to CR/LF. If they are indeed a CR/LF then truncate, else leave it alone. Its not quite a one-liner but still tiny.
[reply]
Re: delete last CR and LF from txt
by ww (Archbishop) on Feb 22, 2010 at 18:11 UTC
    see perldoc perlretut and friends.

    You're looking for a regex anchored to the end of the first line when using read, reverse, regex, re-reverse and write.

[reply]
[d/l]

Back to Seekers of Perl Wisdom