PERL - pattern match

[Pat Tom]

I am writing a PERL script that would search for a pattern in a file. Once the pattern is found, the script should store the portion of the file from the pattern till the end of the file in a buffer for further processing.

I am somehow not able to get the logic.

Can anyone please help.

Thanks,
Pat

[James R. Ferguson]

Hi Pat:

OK, this script meets your requirement. Once a pattern is found, the remainder of a line is stored and every line in the file thereafter. You can do what you wish with the array --- I printed what I stored (buffered) to show the technique.

# cat ./buffer
#!/usr/bin/perl
use strict;
use warnings;
my $pattern = shift;
my $ok;
my @lines;
while (<>) {
chomp;
if (/($pattern)(.*)/) {
push( @lines, $2 );
$ok++;
}
push( @lines, $_ ) if $ok;
}
print "$_\n" for (@lines)

...run as:

# ./buffer local /etc/hosts

...that is, pass the pattern to match followed by the file to be processed.

Regards!

...JRF...

[James R. Ferguson]

Hi Pat:

OK, this script meets your requirement. Once a pattern is found, the remainder of a line is stored and every line in the file thereafter. You can do what you wish with the array --- I printed what I stored (buffered) to show the technique.

# cat ./buffer
#!/usr/bin/perl
use strict;
use warnings;
my $pattern = shift;
my $ok;
my @lines;
while (<>) {
chomp;
if (/($pattern)(.*)/) {
push( @lines, $2 );
$ok++;
}
push( @lines, $_ ) if $ok;
}
print "$_\n" for (@lines)

...run as:

# ./buffer local /etc/hosts

...that is, pass the pattern to match followed by the file to be processed.

Regards!

...JRF...

[Hein van den Heuvel]

Pat,

JRF has the 'de luxe' solution.
If you study it, you'll see it raises (and answer) some questions:

'from the pattern' is that to be taken literally? That is, should it included the pattern itself, or perhaps even the whole 'line' which contained the pattern?

'till the end': What to do with new-lines?


probably not what you need, but here is a one line for the simplest interpretation of the request...

perl -ne '$go++ if /pattern/; print if $go' >

Hein.

[James R. Ferguson]

Hi (again) Pat:

Sorry for the double post. The Forum returned an error in posting the first time --- I should know better.

There is a dumb correction, anyway I need to make! The original solution dropped a 'next' and treated multiple instances of the pattern downstream from the first occurance as reason to chop the beginning of the line again. That's probably not desirable. Hence, use this:

#!/usr/bin/perl
use strict;
use warnings;
my $pattern = shift;
my $ok;
my @lines;
while (<>) {
chomp;
if ( /($pattern)(.*)/ && ! $ok ) {
push( @lines, $2 );
$ok++;
next;
}
push( @lines, $_ ) if $ok;
}
print "$_\n" for (@lines);

Note, however, that you will *miss* the line which *ends* with the pattern sought. According to your specifications, you only want "...from the pattern until the end...". Perhaps you can clarify what behavior you want.

Regards!

...JRF...

[H.Merijn Brand (procura]

# perl -ne'1../pattern/ or print' file > part

Explain what is wrong with that?

Enjoy, Have FUN! H.Merijn

[Peter Nikitka]

Hi Merijn,

your oneliner will not output the line with the first match :-)

mfG Peter