deleting a line from a text file

bory has asked for the wisdom of the Perl Monks concerning the following question:

Hi! i want to delete a certain line from a text file (small one)! I have a form with checkboxes and the line selected(it's only a name) i want to erase it from the text file, but I don't know how to do it!Thank you for your time This what I've tried but it doesn't work at all!

foreach $key(keys(%FORM)){
open OLD, $file or die "Can't open $file:$!\n";
        open NEW, ">$file.new" or die "Can't open temp file $file.new:
+ $!\n";
        my $found =0;
        while (<OLD>) {
            if ($FORM{$key}==1) {
                $found =1;
                next; 
            }
            print NEW; 
        }}
        if ($found) {
            
         rename ("$file.new", $file) or die "Can't rename new $file: $
+!\n";
        } else {
            print "I didn't find !\n";
        }
[download]

Comment on deleting a line from a text file Download Code

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Re: deleting a line from a text file by rinceWind (Monsignor) on Sep 22, 2003 at 10:10 UTC
bory, please can you explain in more detail what you are trying to do. Firstly, the code is iterating keys(%FORM) and doing a sweep of the file for each one. Note, the close brace for this is the second one on the line following `print NEW;` hence the rename doesn't happen until all keys have been processed (overwriting $file.new each time). Secondly, your condition check does not depend on the text in the input file! `if ($FORM{$key}==1) { $found =1; next; }` [download] Finally, you should consider using strict and warnings. This will help you by catching many bugs at source. There are many nodes on PM that describe why strict and warnings are a good thing. Hope this helps, rinceWind -- I'm Not Just Another Perl Hacker	[reply] [d/l] [select]
Re: deleting a line from a text file by zby (Vicar) on Sep 22, 2003 at 09:59 UTC
The loop over the `%FORM` hash keys is really confusing. I think you don't need it. From your description you want to check the lines from the input file against the hash keys, but you never do that. I think you need something like that (not tested): `open OLD, $file or die "Can't open $file:$!\n"; open NEW, ">$file.new" or die "Can't open temp file $file.new: + $!\n"; my $found =0; while (<OLD>) { if ($FORM{$_}==1) { $found =1; next; } print NEW; } } close NEW; close OLD; if ($found) { rename ("$file.new", $file) or die "Can't rename new $file: $ +!\n"; } else { print "I didn't find !\n"; }` [download] What I changed: `if ($FORM{$_}==1)` this is checking if the line is a key in the `%FORM` hash and has a value of 1 (you might change it to `if(exists($FORM{$_}))` if you need to check just existence). Closing the `NEW` and `OLD` filehandles. You could look at File::Atomic if you run this concurrently.	[reply] [d/l] [select]
Re: deleting a line from a text file by CountZero (Bishop) on Sep 22, 2003 at 14:31 UTC
Yes, indeed you have the monks confused! Perhaps it helps if you explain what is in your FORM-hash. What are the keys and their values? How does this hash relate to the text file? Has each line of the file a direct one-to-one relationship with the FORM-hash? How do you go from the check-boxes in your form to the FORM-hash? Am I right in assuming this is something related to a web-page/CGI-script? So many questions ... CountZero "If you have four groups working on a compiler, you'll get a 4-pass compiler." - Conway's Law	[reply]
Re^2: deleting a line from a text file by cis (Initiate) on Mar 14, 2005 at 19:01 UTC
"AB174321","RANDOLPH P. QUINCY",4,75 "BF234567","SANDRA J. RAMERIZ",3,65 "NO381209","KATHLEEN T. ADAMS",5,70 "PQ473215","THOMAS A. STEVENS",2,64 "HZ496531","PATRICIA J. CORY",1,70	[reply]