Category: | Text Processing |
Author/Contact Info | graff |
Description: | This is like the standard unix "uniq" tool to remove lines from an input stream when they match the content of the preceding line, except that the determination of matching content can be limited to specific columns of flat-table data. There's an option to keep just the first matching line or just the last matching line. Note that if the input is not sorted with respect to the column(s) of interest, non-adjacent copies will not be removed (just like with unix "uniq"). (update: note that column delimiters are specifiable by a command-line option)
The code has been updated to avoid the possible "out of memory" condition cited by repellent in the initial reply below. |
#!/usr/bin/perl use strict; use Getopt::Long; use Pod::Usage; my ( $delim, $colspec, $last, $man, $help ) = ( 'default', '1', 0, 0, +0 ); my $argok = GetOptions( 'l' => \$last, 'c=s' => \$colspec, 'd=s' => \$delim, 'm' => \$man, 'h|?' => \$hel +p ); pod2usage(-exitstatus => 0, -verbose => 2) if $man; pod2usage(1) unless ( $argok and $colspec =~ /^\d[\d,]*$/ and !$help a +nd ( @ARGV or !-t )); my @cols = map { $_ -1 } split( /,/, $colspec ); if ( $delim ne 'default' ) { my %ctrl = ( tab => "\t", dot => '\.', vb => '\|', bs => '\\\\' ); $delim = ( exists( $ctrl{$delim} )) ? qr{$ctrl{$delim}} : qr{$deli +m}; } my @lastseen; my $heldline = ''; while (<>) { my @tkns = ( $delim eq 'default' ) ? split : split $delim; my $match = 0; for my $i ( 0 .. $#cols ) { $match++ if ( $tkns[$cols[$i]] eq $lastseen[$i] ); } if ( @cols == $match ) { $heldline = $_ if ( $last ); } else { print $heldline; $heldline = $_; $lastseen[$_] = $tkns[$cols[$_]] for ( 0..$#cols ); } } print $heldline; =head1 NAME col-uniq =head1 SYNOPSIS col-uniq [-l] [-d delim] [-c col#[,col#...]] [sorted.list ...] col-uniq -m # to print user manual =head1 DESCRIPTION This tool will scan through lines of text that have been sorted with respect to one or more selected columns, and in the event that two or more consecutive lines have the same value(s) in the selected column(s), only one line from the matching set will be output. All other lines, having non-repeating values in the selected column(s), are also printed. This tool will only work as intended if the input has been sorted with respect to the column(s) of interest, so a typical usage would be: sort [...] some.list | col-uniq [...] By default, the first whitespace-delimited column will be taken as the column of interest, and for every set of two or more consecutive lines having the same value in that column, only the first line will be printed to STDOUT (along with all the other "unique" lines). Use the "-c col#[,...]" option to select one or more specific columns of interest, by index number (first column on each line is "1"). For example, in a directory where varying numbers of files are created per day, this command line: ls -lt | col-uniq -c 6,7 will show only the first file created on each date. (The "ls" options "-lt" produce a full-detail file list, sorted by date.) Use the "-d delim_regex" option to select something other than whitespace as the delimiter for splitting each line into columns. The given string is passed to the perl "split" function as a regular expression, so a wide assortment of column separation strategies is possible (but bear in mind that the input must be sorted on the basis of the designated columns, in order to locate all duplicates). Also, some "specially defined" split expressions are provided for convenience: -d tab : split on tabs only (not other whitespace) dot : split on period characters vb : split on the vertical-bar (pipe) symbol "|" bs : split on backslash Note that if you set the delimiter to a pattern that never occurs in the data, the result will be to check for (and remove) consecutive full-line duplications. (This will include sets of blank lines.) The "-l" option can be used to preserve only the last line from each set of matching lines (in case that is preferable to keeping only the first). =head1 AUTHOR David Graff =cut |
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Replies are listed 'Best First'. | |
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Re: col-uniq -- remove lines that match on selected column(s)
by repellent (Priest) on Nov 06, 2008 at 00:39 UTC | |
by graff (Chancellor) on Nov 10, 2008 at 02:42 UTC | |
by repellent (Priest) on Nov 10, 2008 at 17:49 UTC | |
Re: col-uniq -- remove lines that match on selected column(s)
by keszler (Priest) on Sep 18, 2011 at 11:04 UTC | |
by graff (Chancellor) on Sep 18, 2011 at 22:17 UTC |
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