By the way, there is a mode in Perl to run like sed, editing files in place. Like in sed, this mode is activated with -i switch, described in perlrun. In a Perl program this mode can be controlled via the $^I variable. There is also special ARGV filehandle which iterates over command-line filenames in @ARGV. It's easy to combine these two to edit a file without slurping it into memory: 

{
 local ($^I, @ARGV) = (".bak", $filename);
 # $filename is renamed to "$filename.bak" and new "$filename" is open
+ed for writing
 while (<>) { # ARGV filehandle is opened to read from "$filename.bak"
  s/foo/bar/g;
  print;
 }
} # at this point @ARGV and $^I are restored to normal

[download]

This might look too low-level. There are modules implementing this behaviour: File::Inplace and IO::InSitu. The latter is described in the Perl Best Practices book by Damian Conway.

In reply to Re: Using read/write to update a file by aitap
in thread Using read/write to update a file by PackerX

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.