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modifying files..

Posted by kitwalker2886 (kitwalker2886), 21 May 2007
hi..its me again.. tell me something.. how can we modify files using perl.?? as in.. i want to open a file.. read the content and modify a part of it.. and store it back in that same file.
   and also.. can i create a new directory and then write to files in it from the program. i tried using mkdir,open dir n then open.. but dint work.

Posted by admin (Graham Ellis), 21 May 2007
You could modify a file "in situ" if you are certain that you'll be replacing a number of bytes with exactly the same number of bytes, but otherwise you'll need to read the old file completely then writ eback to it of (if it's a big file) do a read and write loop, followed by a rename.   Discs aren't like trains where you can always squeeze one more on - once yiou have 512 bytes in a secrot, you can't squeeze any more in!

If you have appropriate permissions, you can create directories, files, etc, from Perl - not a problem at all.   If it's not working, have a look at the special variables such as $@, $? and $! to find out why.

See our more about files and advanced fiel and directory handling pages for many source code examples

Posted by kitwalker2886 (kitwalker2886), 23 May 2007
yeah.. i did that reading and renaming thing that u suggested.. could u tell me a bit more bout modifying them insitu if i m sure i ll be replacing the same number of bytes.. ?? Is there a way to open a file in both read and write mode like in c++..?

Posted by admin (Graham Ellis), 23 May 2007
Yes - the examples in the "advanced file handling" section I linked to in my previous post should help.



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