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POHow to put remove certain line breaks in a file
 

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  1. POHow to put remove certain line breaks in a file
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    <p>I have a file which contains about 70,000 records which is structured roughly like this:</p> <pre><code>01499 1000642 4520101000900000 ...more numbers... 104000900169 +Fieldname1 -Content +Fieldname2 -Content -Content -Content +Fieldname3 -Content -Content +Fieldname4 -Content +Fieldname5 -Content -Content -Content -Content -Content -Content 01473 1000642 4520101000900000 ...more numbers... </code></pre> <p><strong>EDIT 1: Every record thus starts with a column of numbers and ends with a blank line. Before this blank line most records have a <code>+Fieldname5</code> and one or more <code>-Content</code> lines.</strong></p> <p>What I would like to do is to merge all multi-line entries into one line while replacing the leading minus-character by a space <strong>except</strong> those pertaining to the last field (i.e. Fieldname5 in this case).</p> <p>it should look like this:</p> <pre><code>01499 1000642 4520101000900000 ...more numbers... 104000900169 +Fieldname1 -Content +Fieldname2 -Content Content Content +Fieldname3 -Content Content +Fieldname4 -Content +Fieldname5 -Content -Content -Content -Content -Content -Content 01473 1000642 4520101000900000 ...more numbers... </code></pre> <p>what i have now is this (adapted from <a href="https://stackoverflow.com/questions/1523846/how-can-i-print-a-matching-line-one-line-immediately-above-it-and-one-line-immed/1523898#1523898">this answer</a>):</p> <pre><code>use strict; use warnings; our $input = "export.txt"; our $output = "export2.txt"; open our $in, "&lt;$input" or die "$!\n"; open our $out, "&gt;$output" or die "$!\n"; my $this_line = ""; my $new = ""; while(&lt;$in&gt;) { my $last_line = $this_line; $this_line = $_; # if both $last_line and $this_line start with a "-" do the following: if ($last_line =~ /^-.+/ &amp;&amp; $this_line =~ /^-.+/) { #remove \n from $last_line chomp $last_line; #remove leading "-" from $this_line $this_line =~ s/^-//; #join both lines and print them to the file $new = join(' ', $last_line,$this_line); print $out $new; } else { print $out $last_line; } } close ($in); close ($out); </code></pre> <p>but there are 2 problems with this:</p> <ul> <li><p>It correctly prints out the joined line but then still prints out the second line e.g.</p> <p>+Fieldname2 -Content Content Content -Content</p></li> </ul> <p>So how can I make the script only output the joined line?</p> <ul> <li>It only works on two lines at a time, while some of the multi-line entries have up to fourty lines. </li> </ul> <p><strong>EDIT 2:</strong> My question is thus how to do the following:</p> <ol> <li>Read in a file line by line and write it to an output file</li> <li>When a multi-line section appears read and process it in one go, replacing <code>\n-</code> by <code></code><strong>, except if it belongs to a given fieldname (e.g. <code>Fieldname5</code>).</strong></li> <li>Return to reading and writing each line again until another multi-line block appears</li> </ol> <p><strong>EDIT 3:</strong> It worked! I just added another conditional at the beginning: use strict; use warnings;</p> <pre><code>our $input = "export.txt"; our $output = "export2.txt"; open our $in, "&lt;$input" or die "Kann '$input' nicht finden: $!\n"; open our $out, "&gt;$output" or die "Kann '$output' nicht erstellen: $!\n"; my $insideMultiline = 0; my $multilineBuffer = ""; my $exception = 0; # variable indicating whether the current multiline-block is a "special" or not LINE: while (&lt;$in&gt;) { if (/^\+Fieldname5/) { # if line starts with +Fieldname5, set $exception to "1" $exception = 1; } elsif (/^\s/) { # if line starts with a space, set $exception to "0" $exception = "0"; } if ($exception == 0 &amp;&amp; /^-/) { # if $exception is "0" AND the line starts with "-", do the following chomp; if ($insideMultiline) { s/^-/ /; $multilineBuffer .= $_; } else { $insideMultiline = 1; $multilineBuffer = $_; } next LINE; } else { if ($insideMultiline) { print $out "$multilineBuffer\n"; $insideMultiline = 0; $multilineBuffer = ""; } print $out $_; } } close ($in); close ($out); </code></pre>
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