Script to update a value in text file

[amvarma]

This node falls below the community's threshold of quality. You may see it by logging in.

[CountZero]

What have you tried yourself?

[Your Mother]

perl -pe 's/\A([a-z]+)/$i=$1;++$i/e' [filename]

And sno & cno will be incremented. Um… CountZero has a more useful, if less literal, reply, really.

[biohisham]

Welcome to the Monastery, Advising you to try to make your own script that does this job and then once you've fallen short we can pick it up from there as this site is not a code-writing service provider.

Show us what you have tried so far and we'd pick it up from there, but for starters, think about a hash, it is not clear if you want an incrementing that is uniform or random since you've not mentioned that.

Think about reading sno:10 and cno:10 into a hash and increment the hash values...

Also relevant, read How do I post a question effectively?, Markup in the Monastery and Writeup Formatting Tips

[kejohm]

Try Tie::File for editing a file in place via a Perl array.

Update: Link fixed.

[Boldra]

in-place-edit is appropriate (YourMother's reply), but just because I'm still amazed at how cool IO::All is:

perl -MIO::All -E 's/(\d+)/$1+1/e for @{io("/tmp/amvarma.txt")}'

[Marshall]

The file on disk is a sequence of bytes. You can't simply insert or delete bytes because all the bytes after that have to be moved.

For a small file, read the file into memory, make modifications as you will and then re-write the file. You may want to make some sort of backup scheme so that if your program dies while re-writing the file, the orginal data can still be recovered (i.e. don't delete, file and re-write with the same name because if that write fails, all data is lost).

[JavaFan]

Can I get some help, how to go about in implementing this?

First, I'd learn a language of my choice. Then, in said language, I would:
1. Get coffee (I recommend Java).
2. Open the original file for reading.
3. Open a new file for writing.
4. Read in the original file, in chunks.
5. For each chunk:
   1. Locate data I want to modify.
   2. Change the chunk so the value is incremented.
   3. Write the modified chunk to the new file.
6. Close both open files.
7. Move the new file over the original one.
8. Finish coffee.
9. Profit!

[apl]

6a. Rename original file (so it's still around for post mortems)

[Khen1950fx]

This increments sno and cno, but I did this just for fun.

#!/usr/bin/perl

use strict;
use warnings;
use Tie::CountLoop;

tie my $counter, 'Tie::CountLoop', 'sno:10'; 
tie my $counter1, 'Tie::CountLoop', 'cno:20';

my $t = tied $counter;
my $t1 = tied $counter1;
$t->auto(1);
$t1->auto(1);
print "    <<$counter>>:10    \n",
      "    <<$counter1>>:20    \n";