in reply to Re: improve script
in thread improve script

print "$1\n" and exit if /.../

Funny to read, but not funny when printing fails for some reason:print and exit exists ONLY if print was successful.

>cat print-and-exit.pl
#!/usr/bin/perl

use strict;
use warnings;

close STDOUT if @ARGV;

1 and print "foo" and exit 0;
die "Ooops, still here";

>perl print-and-exit.pl
foo
>perl print-and-exit.pl kaboom
print() on closed filehandle STDOUT at print-and-exit.pl line 8.
Ooops, still here at print-and-exit.pl line 9.

>

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Alexander

--
Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)

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Re^3: improve script
by LanX (Saint) on Nov 28, 2015 at 21:36 UTC
    I must be too ignorant to see why STDOUT should be closed in a one-liner (???)

    Anyway it's true is that chaining with and is a lazy way to avoid the already mentioned scalar comma operator:

      print, exit if cond

    This seems to confuse many people, but has the same effect as

      do {print; exit} if cond

    Cheers Rolf
    (addicted to the Perl Programming Language and ☆☆☆☆ :)
    Je suis Charlie!

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      I must be too ignorant to see why STDOUT should be closed

      Closing STDOUT was a simple way to make print fail, nothing more. There are several other ways how print can fail. A simple one is running out of disk space while STDOUT is redirected to a file. But I was too lazy to show creating, formatting, mounting, and filling a loop device just to show that print may fail. A third one is a disappearing block device - unplugging the wrong USB stick or harddisk. Number four: a failing disk. Number five: Disk quotas. Number six: Network disconnected while writing to a remote filesystem.

      in a one-liner (???)

      I never limited my post to one-liners. print and exit is problematic in one-liners as well as in scripts and modules, because it does not always exit, but it may look like it does. And, as posted in Re^5: improve script, the proper way to terminate a script with an error message is to use die. It writes the error message to where it belongs: STDERR.

      Alexander

      --
      Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)
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Re^3: improve script
by choroba (Cardinal) on Nov 28, 2015 at 00:40 UTC
    So, what's your solution? 
    ($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,

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      if ( somecondition ) {
    print "...";
    exit;
}

      [download]

      Alexander

      --
      Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)
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        Or just:

        print( "$1\n" ), exit if /.../;

        [download]

        Or even:

        die "$!\n" if /.../;

        [download]

        Which seems to capture the semantics perfectly.

        With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
        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". I knew I was on the right track :)
        In the absence of evidence, opinion is indistinguishable from prejudice.
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        It wouldn't print anything if STDOUT was closed, though. 
        ($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,

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