I have a long script that uses print (to STDOUT) in various places to print data to a terminal. Now I need to add a 'grep' option within the script so that only lines that match a certain regular expression are printed; all the rest are not printed.

I would be OK with adding a new FILEHANDLE in front of every print statement, but I would want to avoid calling my own print subroutine every time I want to do a print. So something like this would be OK (only the first line should be printed in STDOUT, the second would not be printed):

my $GREP_STR = "123"; ## a global var

print GREP_FH "My line with 123\n"; ## anywhere in the code
print GREP_FH "My line with 456\n";

[download]

but not this

&myprint("My line with 123\n");
&myprint("My line with 456\n");

[download]

Ideally I would also want the ability to print lines that override the 'grep' and are printed anyway, but that's optional. So something like this:

$GREP_STR = '123';

print STDOUT "Header - always print this\n";
print GREP_FH "My line with 123\n";    ## printed at the terminal
print GREP_FH "My line with 456\n";    ## not printed

[download]

I thought that by using 'select' I could auto-redirect the STDOUT to maybe a subroutine, and then decide there if I want to print something or not, but it seems like 'select' only redirects to an actual FILEHANDLE and can't redirect to a subroutine.

In reply to Preprocessing print statements by mauroid

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.