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Remove First line from File

andy7t
User

Jan 30, 2004, 9:29 AM

Post #1 of 5 (613 views)

Remove First line from File	Can't Post

Hello,

I have a large file, with many lines in (about 50,000).

I need to remove the first line from that file each time it is run.

Normally i would consider:

$num=0;
foreach $line (@line)
{
next if $num eq "0";

print LIST "$line\n";
$num++;
}

However i think with 50,000 lines this is not a good idea.

Is it not possible just to remove the first line from a file simply?

davorg
Thaumaturge / Moderator

Jan 30, 2004, 10:46 AM

Post #2 of 5 (611 views)

Re: [andy7t] Remove First line from File [In reply to]	Can't Post

The easiest way is probably to look at Tie::File which has been included with Perl since version 5.8.0.

But your code can be made a bit simpler

Code

print LIST map { "$_\n" } @line[1 .. $#line];

Or perhaps

Code

shift @line; 
print LIST map { "$_\n" } @line;

--
Dave Cross, Perl Hacker, Trainer and Writer
http://www.dave.org.uk/
Get more help at Perl Monks

Recall
Novice

Jan 30, 2004, 5:56 PM

Post #3 of 5 (609 views)

Re: [davorg] Remove First line from File [In reply to]	Can't Post

...which is a memory hog for 50,000 lines.

davorg
Thaumaturge / Moderator

Jan 31, 2004, 1:07 AM

Post #4 of 5 (606 views)

Re: [Recall] Remove First line from File [In reply to]	Can't Post

Of yes. Of course it is. But he'd already read the whole file into an array so the damage was done :)

But my first suggestion was Tie::File, which _wouldn't_ read the whole file into memory.

--
Dave Cross, Perl Hacker, Trainer and Writer
http://www.dave.org.uk/
Get more help at Perl Monks

Recall
Novice

Jan 31, 2004, 4:07 AM

Post #5 of 5 (604 views)

Re: [davorg] Remove First line from File [In reply to]	Can't Post

Quote

But he'd already read the whole file into an array so the damage was done :)

Then you should point out to him not to do that rather than allowing him to continue with it =)

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