Re: File I/O

your attempt only opens the file for read, not write.

open RECORD_NUMBER, '<', "counter_data.dat" or die;
$count = <RECORD_NUMBER>;
close RECORD_NUMBER;
$count++
open FILE, '>', "counter_data.dat" or die;
print FILE $count;
close FILE;
[download]

Have to ask, WHY do you need to do this? (there may be a far better/more robust way to accomplish your specifc task)

alternative cmd-line way (see perlrun for the switches):

perl -i -pe '++$_' counter.dat
[download]

Comment on Re: File I/O Select or Download Code

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Re^2: File I/O by Melly (Chaplain) on Jan 17, 2007 at 22:46 UTC
Maybe, maybe not. For simple jobs run from a cron or similiar, where locking may not be an issue, a simple counter file can often be the most suitable solution (esp. where ease of distrib. is an issue). IMHO, needless to say, but KISS. `map{$a=1-$_/10;map{$d=$a;$e=$b=$_/20-2;map{($d,$e)=(2$d$e+$a,$e2 -$d2+$b);$c=$d2+$e2>4?$d=8:_}1..50;print$c}0..59;print$/}0..20` [download] Tom Melly, pm@tomandlu.co.uk	[reply] [d/l]
Re^2: File I/O by Anonymous Monk on Jan 18, 2007 at 03:59 UTC
First: Thanks to everyone who responded--so quickly!! This is sort of the blind leading the blind...I wrote a short PERL CGI script to give a truly non-programming person the ability to use a simple form that accepts input and creates an html file (which builds a table of data). My first crack at the CGI has very limited error checking. As I look to improve it, I figured I could capture the date and also increment the record entry counter so Patty only has to worry about a few entry fields. She is the only person besides myself that will probably ever use this. I guess I managed to do a couple things right...my die statements actually have a descriptive string with them. The way I opened the file threw me because a couple variations "did" write, but was incorrect. thanks again, I'm confident this will work. Can't wait to try it out in the office.	[reply]
Re^2: File I/O by blazar (Canon) on Jan 18, 2007 at 10:24 UTC
your attempt only opens the file for read, not write. `open RECORD_NUMBER, '<', "counter_data.dat" or die; $count = <RECORD_NUMBER>; close RECORD_NUMBER; $count++ open FILE, '>', "counter_data.dat" or die; print FILE $count; close FILE;` [download] I see most people answered along these lines. It is worth mentioning open `'+<'` mode too, although in that case one would have to seek as well.	[reply] [d/l] [select]