Perl next if @array (exclude a list of values)

Shell Programming and Scripting
1

I'm trying to exlude a list of values with perl to process while reading in a file. Is there a way to use the

next if

with a list?

Example:

@array = qw(val1 val2 val3 val6);

while (<>) {
 next if $_ =~ @array;	# values I don't want to process here
 print;			# process the rest here
}

Thanks in advance!

2

Any time you want to quickly check if something is in a list, use a hash...

%hash=(val1 => 1, val2 => 1,  val3 => 1,  val6 => 1, ); # hash with unwanted items as keys and values that evaluate as true
while (<>) {
 next if $hash{$_};	# values you don't want to process are skipped here
 print;			# process the rest here
}
2 Likes
3

Using grep

@arry = qw (val1 val2 val3 val3);
while (<>){
  $line=$_;
  next if (grep(/$line/,@arry));
  print ;
}
4

Hi Pravin,

That will work however, while it will use less memory than a hash, it will use a lot more cycles. you are grepping through the (potentially large array) for every line of the file.

Where you have a static list you wish check against a hash is the preferred solution as you take advantage of the hashing to very quickly return the value.

2 Likes
5

Will this work with a range?

%hash=(val1 => 1, val2 => 1,  val3 => 1,  val6 => 1, ); # hash with unwanted items as keys and values that evaluate as true
while (<>) {
 print if (/$hash{$_}/ .. /END/);	
}
6

I am afraid it will not work, regardless of what you are trying to do.
$_ in the while loop will have a new line with it and it will never match any of the %hash keys.
$hash{$_} will evaluate to a 1 if exist and to undef if it doesn't, thus /1/ .. /END/ or /undef/ .. /END/ , which makes a moot condition.

What is it that you are trying to do? The latest seems off from your original query.
Could you post input and desired output examples?

7

Yes and Thanks.
I'm trying to remove sections of a file based on an input of values.

Here is a sample of the file I'm trying to "edit"

section /total/SMS-MT-FSM-DEL-REP045
country: IN
1280363645.979354_PFS_1_1887728354
begin:03
final:56
END

section /total/SMS-MO-FSM001
country: IR
1280105721.484103_PFM_1_1187616097
final:23
END

section /total/SMS-MT-FSM-DEL-REP095
country: IN
1280363645.729309_PFS_1_1084296392
final:43
END

section /total/SMS-MO-FSM001
country: IR
1280105721.484103_PFM_1_1187616097
final:23
END

section /total/SMS-MO-FSM095
country: MO
1280105721.461090_PFM_1_882824215
begin:12
final:89
END

With a list given to me as:

REP045
REP095

I want to remove the sections of the file related to a list given above.

Desired output:

section /total/SMS-MO-FSM001
country: IR
1280105721.484103_PFM_1_1187616097
final:23
END

section /total/SMS-MO-FSM095
country: MO
1280105721.461090_PFM_1_882824215
begin:12
final:89
END
8

Given your explanation this should be able to do it. However, your desired output does not match what you explained.

#!/usr/bin/perl
#
use strict;
use warnings;

my @list = qw(REP045 REP095);
my %unwanted = map{$_ => 1} @list;

{
    local $/="\n\n";
    while(<>) {
        my ($id) = (split '-', (split '\n')[0])[-1];
        print if /$id/ and not $unwanted{$id};
    }
}

section /total/SMS-MO-FSM001
country: IR
1280105721.484103_PFM_1_1187616097
final:23
END

section /total/SMS-MO-FSM001
country: IR
1280105721.484103_PFM_1_1187616097
final:23
END

section /total/SMS-MO-FSM095
country: MO
1280105721.461090_PFM_1_882824215
begin:12
final:89
END
1 Like
9

Thanks much, Aia! I appreciate you looking at this for me!