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

Hi Monks :-)

I have strings of varying length. I would like to find out the length, and remove all characters after the 17th. Then when I have a string of 17 characters, I would like to append '...' to the end of the string.

For example:

Old string: 'hello world, goodbye world'
Chop off after 17 characters: 'hello world, good'
Now append 3 periods: 'hello world, good...'

Any ideas? Thanks,
Gavin

Replies are listed 'Best First'.
Re: truncating a line
by ctilmes (Vicar) on Jul 01, 2003 at 13:56 UTC
    use the substr() as an lvalue: 
    substr($str, 17) = '...' if length $str > 17;

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[d/l]
Re: truncating a line
by tilly (Archbishop) on Jul 01, 2003 at 13:52 UTC
    Use length to find the length, and then substr to chop it.

    BTW a tip. It works slightly more smoothly if you only chop and add the dots if the string is over 20 characters.

[reply]
      BTW a tip. It works slightly more smoothly if you only chop and add the dots if the string is over 20 characters.
      What exactly do you mean by this?
      is there a technical reason,
      or because it cuts a word in half with that particular string,
      or in your experience 20 chars is best to still leave the string reasonably understandable?

      Cheers,
      fireartist
[reply]
        Because truncating and adding 3 dots leaves the length of the string at 20 chars. Why bother truncating and indicating a continuation unless you are going to wind up with a shorter string for the loss of information?

        Trust me. This is a detail that users tend to notice.

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Re: truncating a line
by dreadpiratepeter (Priest) on Jul 01, 2003 at 13:51 UTC
    untested:
    
$str = length($str)>17 ? substr($str,0,17).'...' : $str;

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    -pete
    "Worry is like a rocking chair. It gives you something to do, but it doesn't get you anywhere."
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[d/l]
Re: truncating a line
by particle (Vicar) on Jul 01, 2003 at 13:55 UTC

    you'll want to use substr:

    my $long_line= 'this line is more than seventeen characters.';
my $short_line= substr( $long_line, 16, length $long_line ) .= '...';

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    ~Particle *accelerates*

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Re: truncating a line
by BrowserUk (Patriarch) on Jul 01, 2003 at 14:16 UTC

    TIMTOWTDI...

    $line = $1 . '...' if $line =~ m[^(.{17})];

    [download]

    ...but ctilmes method above is the right way:)

    Update: Corrected (another) typo pointed out by sauoq .

    Examine what is said, not who speaks.
    "Efficiency is intelligent laziness." -David Dunham
    "When I'm working on a problem, I never think about beauty. I think only how to solve the problem. But when I have finished, if the solution is not beautiful, I know it is wrong." -Richard Buckminster Fuller


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Re: truncating a line
by hardburn (Abbot) on Jul 01, 2003 at 14:17 UTC

    Just to be different:

    # $str defined elsewhere 
$str =~ s/\A
    (.{0,17})
    (.*)       # Normal rules about .* don't apply--we 
               # really do need everything that's left
\z/$1(?($2) \. \. \.)/x;

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    Update: Never mind. Doesn't work.

    ----
    I wanted to explore how Perl's closures can be manipulated, and ended up creating an object system by accident.
    -- Schemer

    Note: All code is untested, unless otherwise stated

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Re: truncating a line
by svsingh (Priest) on Jul 01, 2003 at 15:26 UTC
    I haven't seen anyone answer with this one yet, so I thought I'd throw it out there. Sorry if it's a repeat. I'm not as proficient with all the regex tricks as I'd like to be. 
    $line =~ /^(.{0,17})/;
print "$1\n";

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    If that's a rehash, then please let me know. I think it's close to BrowserUK's answer, but they have an if that mine doesn't. Thanks.

[reply]
[d/l]
      Removing an if is only worthwhile if you still have a correct solution.

      Yours does not add the requested "..." when it is needed. (And like the other RE solution will also mess up if there is a newline in there.)

[reply]
        Argh. Thanks tilly. I was so jazzed that I knew how to approach the first half, I overlooked the second. Read the spec, read the spec, read the spec.
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