Re: How do I add a few stings of text, 30 lines before the EOF?

Do you always know the length of the file, and know which line you want to put it in? If so:

#!/usr/bin/perl -wT

use strict;

#get inserted text
my @inserted_text = ('Blah','Blah Blah');

# read in the file
open (FILE,"filename") or die "Can't open file";
my @file = <FILE>
close(FILE)

open (OUTFILE,">filename") or die "Can't open file";
my $line = 0;
foreach(@file) {
    if ($line = 569) {
       foreach(@inserted_text){print OUTFILE;}
     }
    $line++;
}
close(OUTFILE);
[download]

Otherwise, you could find out the length of the file, and then subtract 30 from the end of the length, and insert it there.

This is untested code and, I'd bet 70 monks here could give you much, much better answers. I look forward to seeing them.

Comment on Re: How do I add a few stings of text, 30 lines before the EOF? Download Code

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Re: Re: How do I add a few stings of text, 30 lines before the EOF? (update) by lucasdmc (Initiate) on Oct 16, 2001 at 04:02 UTC
Here's some updated information about my problem: The file I need to modify currently has 1107 lines. I need to insert 2 lines, 30 lines before the EOF --making the new line total 1109. So the file would continually get larger (1111, 1113, ...). I found that the 30 lines I'm trying to insert before, are exactly 947 bytes in length. Hopefully this information will help,	[reply]
Re: Re: Re: How do I add a few stings of text, 30 lines before the EOF? (update) by wog (Curate) on Oct 16, 2001 at 04:32 UTC
Knowing exactly what byte location you want to insert at, you can seek to that location, read in the final bytes of the file, go back to that location and write out the new lines and the final bytes. To give some code: use Fcntl qw(:seek :flock); # get constants # location suitable for direct use in seek. use constant INSERT_LOCATION => (-947, SEEK_END); my $file = "..."; # open the file for update open FILE, "+<$file" or die "couldn't open $file: $!\n"; # don't have two copies of us update the file at the # same time... flock FILE, LOCK_EX or die "flock: $!\n"; # go to our location seek FILE, INSERT_LOCATION or die "seek: $!\n"; # read the rest of the file from there my $end = do { local $/; <FILE> }; defined $end or die "read: $!\n"; # go back to our location seek FILE, INSERT_LOCATION or die "seek: $!\n"; # write new data followed by old data from that point. print FILE $newlines, $end or die "print: $!\n"; close FILE or warn "close: $!\n"; [download] (I'm being incredibly paranoid by checking the return value of print and readline and close. You probably don't have to be.) Be forewarned that if the byte location is or becomes wrong then file curruption is likely.	[reply] [d/l]