in reply to Use Perl's Sort to only sort certain lines in a file?

If I understand you correctly, you want to keep each section in place, and only sort the entries under the bracketed line. If that is the case, then one way to do that would be:

my @unsorted_input;

while (my $line = <Input>) {
    if ($line =~ /\A\[/) {      # line starts with a bracket
        if (@unsorted_input) {  # if array has entries
            >>>call your sort routine here<<<
            print @unsorted_input;
            undef @unsorted_input;
        }
        print $line;            # print the header line
    } else {                    # line is an entry line
        push @unsorted_input, $line;
    }
}
>> your sort routine <<         # added code per soonix's correction
print @unsorted_input;

[download]

How it works: The program will keep each section heading line (with the brackets) in place. All of the other lines for that section will go into your array. Once the next section line is encountered, the program will sort the entry lines currently in the array (for the last section), print them, then print the next section line and repeat the process.

Update: I know the code looks backward, but when the first header line is encounterd, there will be no data in the array, so the array printing will be skipped and just the header line gets printed. After accumulating the entries for that section in the array, then when the next section header is encountered, the array gets printed, followed by the section header.

Update 2: Updated code per soonix's correction below

--Nick

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Re^2: Use Perl's Sort to only sort certain lines in a file?
by soonix (Chancellor) on Jan 01, 2015 at 20:25 UTC
    ++, but if the input doesn't end with a "section" line, the last block will not be printed, so you have to put 
    >>>call sort routine<<<
print @unsorted_input;

    [download]
    after the loop...
[reply]
[d/l]

      I knew I was missing something...

      --Nick
[reply]
Re^2: Use Perl's Sort to only sort certain lines in a file?
by grahambuck (Acolyte) on Jan 02, 2015 at 01:01 UTC

    Nick,

    Thanks for your help. Would you (or someone else) be able to help me further?

    I'm using BBEdit as my text editor. When I copied your code and made a few edits (see below, NB. the html character code is that shift-opt-5 character) my outputted text became everything in the "if" section. The program then popped open a Unix Script Log window and contained within it is everything from the "else" section. However, nothing in this Log output is sorted.

    while (my $line = <Input>) {
    $line =~ s{(z0)}{&#64257;$1}g;
#     $line =~ s{(?<=^)\n\Z}{&#64257;\n}g;
    if ($line =~ /^&#64257;/) {       # line starts with a bracket
        if (@unsorted_input) {  # if array has entries
#             my @sorted = sort two_way_sort @unsorted_input;
            print @unsorted_input;
            undef @unsorted_input;
        }
        print {Output} $line;            # print the header line
    }
    else {                       # line is an entry line
        my @sorted = sort two_way_sort @unsorted_input;
        push @unsorted_input, $line;
    }
}


foreach my $line (@unsorted_input) {
    print Output $line;
}

    [download]

    I'm not certain about what to do next.

[reply]
[d/l]

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