FAQ 3.23 Can I write useful Perl programs on the command line?

Discussion in 'Perl Misc' started by PerlFAQ Server, Mar 5, 2011.

  1. This is an excerpt from the latest version perlfaq3.pod, which
    comes with the standard Perl distribution. These postings aim to
    reduce the number of repeated questions as well as allow the community
    to review and update the answers. The latest version of the complete
    perlfaq is at http://faq.perl.org .

    --------------------------------------------------------------------

    3.23: Can I write useful Perl programs on the command line?

    Yes. Read perlrun for more information. Some examples follow. (These
    assume standard Unix shell quoting rules.)

    # sum first and last fields
    perl -lane 'print $F[0] + $F[-1]' *

    # identify text files
    perl -le 'for(@ARGV) {print if -f && -T _}' *

    # remove (most) comments from C program
    perl -0777 -pe 's{/\*.*?\*/}{}gs' foo.c

    # make file a month younger than today, defeating reaper daemons
    perl -e '$X=24*60*60; utime(time(),time() + 30 * $X,@ARGV)' *

    # find first unused uid
    perl -le '$i++ while getpwuid($i); print $i'

    # display reasonable manpath
    echo $PATH | perl -nl -072 -e '
    s![^/+]*$!man!&&-d&&!$s{$_}++&&push@m,$_;END{print"@m"}'

    OK, the last one was actually an Obfuscated Perl Contest entry. :)



    --------------------------------------------------------------------

    The perlfaq-workers, a group of volunteers, maintain the perlfaq. They
    are not necessarily experts in every domain where Perl might show up,
    so please include as much information as possible and relevant in any
    corrections. The perlfaq-workers also don't have access to every
    operating system or platform, so please include relevant details for
    corrections to examples that do not work on particular platforms.
    Working code is greatly appreciated.

    If you'd like to help maintain the perlfaq, see the details in
    perlfaq.pod.
    PerlFAQ Server, Mar 5, 2011
    #1
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