FAQ 5.4 How can I use Perl's "-i" option from within a program?

Do you have a question? Post it now! No Registration Necessary.  Now with pictures!

This message is one of several periodic postings to comp.lang.perl.misc
intended to make it easier for perl programmers to find answers to
common questions. The core of this message represents an excerpt
from the documentation provided with Perl.


5.4: How can I use Perl's "-i" option from within a program?

    "-i" sets the value of Perl's $^I variable, which in turn affects the
    behavior of "<>"; see perlrun for more details. By modifying the
    appropriate variables directly, you can get the same behavior within a
    larger program. For example:

         # ...
            local($^I, @ARGV) = ('.orig', glob("*.c"));
            while (<>) {
               if ($. == 1) {
                   print "This line should appear at the top of each file\n";
               s/\b(p)earl\b/erl/i;        # Correct typos, preserving case
               close ARGV if eof;              # Reset $.
         # $^I and @ARGV return to their old values here

    This block modifies all the ".c" files in the current directory, leaving
    a backup of the original data from each file in a new ".c.orig" file.


Documents such as this have been called "Answers to Frequently
Asked Questions" or FAQ for short.  They represent an important
part of the Usenet tradition.  They serve to reduce the volume of
redundant traffic on a news group by providing quality answers to
questions that keep coming up.

If you are some how irritated by seeing these postings you are free
to ignore them or add the sender to your killfile.  If you find
errors or other problems with these postings please send corrections
or comments to the posting email address or to the maintainers as
directed in the perlfaq manual page.

Note that the FAQ text posted by this server may have been modified
from that distributed in the stable Perl release.  It may have been
edited to reflect the additions, changes and corrections provided
by respondents, reviewers, and critics to previous postings of
these FAQ. Complete text of these FAQ are available on request.

The perlfaq manual page contains the following copyright notice.


    Copyright (c) 1997-2002 Tom Christiansen and Nathan
    Torkington, and other contributors as noted. All rights

This posting is provided in the hope that it will be useful but
does not represent a commitment or contract of any kind on the part
of the contributers, authors or their agents.

Site Timeline