Input:
orf00007 PHAGE_Prochl_MED4_213_NC_020845-gi|472340344|ref|YP_007673870.1| 7665 8618 0.210897481636936
orf00007 PHAGE_Prochl_MED4_213_NC_020845-gi|472340344|ref|YP_007673870.1| 7665 8618 0.210897481636936
orf00007 PHAGE_Prochl_P_HM2_NC_015284-gi|326783200|ref|YP_004323597.1| 7665 8618 0.207761175236097
orf00015 PHAGE_Megavi_lba_NC_020232-gi|448825467|ref|YP_007418398.1| 11594 13510 0.278721920668058
orf00015 PHAGE_Acanth_moumouvirus_NC_020104-gi|441432357|ref|YP_007354399.1| 11594 13510 0.278721920668058
The script I had implemented:
use feature qw/say/;
use Math::Trig;
open FILE,"out02.txt";
my #file=<FILE>;
close FILE;
my $aa=0;
for(my $i=$aa; $i <=17822; $i++){
if (($file[$i]>=0.210)){
open(OUTFILE,'>>OUT_t10-t10.txt');
print OUTFILE $file[$i];
}
else{}
}
Note:
I need to take the last column as the analysing criteria to print the entire row(the float value, eg:0.210897481636936)
for example if the user input value is '0.210',it has to produce >= values rows ,the expected output is
Output:
orf00007 PHAGE_Prochl_MED4_213_NC_020845-gi|472340344|ref|YP_007673870.1| 7665 8618 0.210897481636936
orf00007 PHAGE_Prochl_MED4_213_NC_020845-gi|472340344|ref|YP_007673870.1| 7665 8618 0.210897481636936
orf00015 PHAGE_Megavi_lba_NC_020232-gi|448825467|ref|YP_007418398.1| 11594 13510 0.278721920668058
orf00015 PHAGE_Acanth_moumouvirus_NC_020104-gi|441432357|ref|YP_007354399.1| 11594 13510 0.278721920668058
A script like the following could work for you:
use strict;
use warnings;
use autodie;
die "Usage: $0 number file\n"
if #ARGV != 2;
my $minval = shift;
while (<>) {
my #cols = split;
print if $col[-1] >= $minval;
}
And execute it like:
perl yourscript.pl 0.210 out02.txt >> OUT_t10-t10.txt
Or using a perl one-liner:
perl -lane 'print if $F[-1] >= 0.210' out02.txt >> OUT_t10-t10.txt
Using awk:
awk -v value=0.210 '$NF >= value' file
Or
awk -v value=0.210 '$NF >= value' file > output_file
This scripts (inspired on yours) solves the problem:
use strict;
use warnings;
my $user_filter = 0.21;
open my $input_file, "<", "out02.txt" or die $!; # Modern way of open files
open my $output_file, ">>", "OUT_t10-t10.txtt" or die $!;
while( my $line=<$input_file> ) {
if( $line =~ / ([\d\.]+)\s*$/ ) {
# If a number was found at the end of line
if( $1 > $user_filter ) { # Check condition
print $output_file $line; #Write to output file
}
}
}
close $input_file;
close $output_file;
Related
I would like to know of a fast/efficient way in any program (awk/perl/python) to split a csv file (say 10k columns) into multiple small files each containing 2 columns. I would be doing this on a unix machine.
#contents of large_file.csv
1,2,3,4,5,6,7,8
a,b,c,d,e,f,g,h
q,w,e,r,t,y,u,i
a,s,d,f,g,h,j,k
z,x,c,v,b,n,m,z
I now want multiple files like this:
# contents of 1.csv
1,2
a,b
q,w
a,s
z,x
# contents of 2.csv
1,3
a,c
q,e
a,d
z,c
# contents of 3.csv
1,4
a,d
q,r
a,f
z,v
and so on...
I can do this currently with awk on small files (say 30 columns) like this:
awk -F, 'BEGIN{OFS=",";} {for (i=1; i < NF; i++) print $1, $(i+1) > i ".csv"}' large_file.csv
The above takes a very long time with large files and I was wondering if there is a faster and more efficient way of doing the same.
Thanks in advance.
The main hold up here is in writing so many files.
Here is one way
use warnings;
use strict;
use feature 'say';
my $file = shift // die "Usage: $0 csv-file\n";
my #lines = do { local #ARGV = $file; <> };
chomp #lines;
my #fhs = map {
open my $fh, '>', "f${_}.csv" or die $!;
$fh
}
1 .. scalar( split /,/, $lines[0] );
for (#lines) {
my ($first, #cols) = split /,/;
say {$fhs[$_]} join(',', $first, $cols[$_])
for 0..$#cols;
}
I didn't time this against any other approaches. Assembling data for each file first and then dumping it in one operation into each file may help, but first let us know how large the original CSV file is.
Opening so many output files at once (for #fhs filehandles) may pose problems. If that is the case then the simplest way is to first assemble all data and then open and write a file at a time
use warnings;
use strict;
use feature 'say';
my $file = shift // die "Usage: $0 csv-file\n";
open my $fh, '<', $file or die "Can't open $file: $!";
my #data;
while (<$fh>) {
chomp;
my ($first, #cols) = split /,/;
push #{$data[$_]}, join(',', $first, $cols[$_])
for 0..$#cols;
}
for my $i (0..$#data) {
open my $fh, '>', $i+1 . '.csv' or die $!;
say $fh $_ for #{$data[$i]};
}
This depends on whether the entire original CSV file, plus a bit more, can be held in memory.
With your show samples, attempts; please try following awk code. Since you are opening files all together it may fail with infamous "too many files opened error" So to avoid that have all values into an array and in END block of this awk code print them one by one and I am closing them ASAP all contents are getting printed to output file.
awk '
BEGIN{ FS=OFS="," }
{
for(i=1;i<NF;i++){
value[i]=(value[i]?value[i] ORS:"") ($1 OFS $(i+1))
}
}
END{
for(i=1;i<=NF;i++){
outFile=i".csv"
print value[i] > (outFile)
close(outFile)
}
}
' large_file.csv
I needed the same functionality and wrote it in bash.
Not sure if it will be faster than ravindersingh13's answer, but I hope it will help someone.
Actual version: https://github.com/pgrabarczyk/csv-file-splitter
#!/usr/bin/env bash
set -eu
SOURCE_CSV_PATH="${1}"
LINES_PER_FILE="${2}"
DEST_PREFIX_NAME="${3}"
DEBUG="${4:-0}"
split_files() {
local source_csv_path="${1}"
local lines_per_file="${2}"
local dest_prefix_name="${3}"
local debug="${4}"
_print_log "source_csv_path: ${source_csv_path}"
local dest_prefix_path="$(pwd)/output/${dest_prefix_name}"
_print_log "dest_prefix_path: ${dest_prefix_path}"
local headline=$(awk "NR==1" "${source_csv_path}")
local file_no=0
mkdir -p "$(dirname ${dest_prefix_path})"
local lines_in_files=$(wc -l "${source_csv_path}" | awk '{print $1}')
local files_to_create=$(((lines_in_files-1)/lines_per_file))
_print_log "There is ${lines_in_files} lines in file. I will create ${files_to_create} files per ${lines_per_file} (Last file may have less)"
_print_log "Start processing."
for (( start_line=1; start_line<=lines_in_files; )); do
last_line=$((start_line+lines_per_file))
file_no=$((file_no+1))
local file_path="${dest_prefix_path}$(printf "%06d" ${file_no}).csv"
if [ $debug -eq 1 ]; then
_print_log "Creating file ${file_path} with lines [${start_line};${last_line}]"
fi
echo "${headline}" > "${file_path}"
awk "NR>${start_line} && NR<=${last_line}" "${source_csv_path}" >> "${file_path}"
start_line=$last_line
done
_print_log "Done."
}
_print_log() {
local log_message="${1}"
local date_time=$(date "+%Y-%m-%d %H:%M:%S.%3N")
printf "%s - %s\n" "${date_time}" "${log_message}" >&2
}
split_files "${SOURCE_CSV_PATH}" "${LINES_PER_FILE}" "${DEST_PREFIX_NAME}" "${DEBUG}"
Execution:
bash csv-file-splitter.sh "sample.csv" 3 "result_" 1
Tried a solution using the module Text::CSV.
#! /usr/bin/env perl
use warnings;
use strict;
use utf8;
use open qw<:std :encoding(utf-8)>;
use autodie;
use feature qw<say>;
use Text::CSV;
my %hsh = ();
my $csv = Text::CSV->new({ sep_char => ',' });
print "Enter filename: ";
chomp(my $filename = <STDIN>);
open (my $ifile, '<', $filename);
while (<$ifile>) {
chomp;
if ($csv->parse($_)) {
my #fields = $csv->fields();
my $first = shift #fields;
while (my ($i, $v) = each #fields) {
push #{$hsh{($i + 1).".csv"}}, "$first,$v";
}
} else {
die "Line could not be parsed: $_\n";
}
}
close($ifile);
while (my ($k, $v) = each %hsh) {
open(my $ifile, '>', $k);
say {$ifile} $_ for #$v;
close($ifile);
}
exit(0);
I'm very new to Perl and am working on a Bioinformatics project at University. I have FILE1 containing a list of positions, in the format:
99269
550
100
126477
1700
And FILE2 in the format:
517 1878 forward
700 2500 forward
2156 3289 forward
99000 100000 forward
22000 23000 backward
I want to compare every position in FILE1 to every range in values on FILE2, and if a position falls into one of the ranges then I want to print the position, range and direction.
So my expected output would be:
99269 99000 100000 forward
550 517 1878 forward
1700 517 1878 forward
Currently it will run with no errors, however it doesn't output any information so I am unsure where I am going wrong! When I split the final 'if' rule it runs but will only work if the position is on exactly the same line as the range.
My code is as follows:
#!/usr/bin/perl
use strict;
use warnings;
my $outputfile = "/Users/edwardtickle/Documents/CC22CDS.txt";
open FILE1, "/Users/edwardtickle/Documents/CC22positions.txt"
or die "cannot open > CC22: $!";
open FILE2, "/Users/edwardtickle/Documents/CDSpositions.txt"
or die "cannot open > CDS: $!";
open( OUTPUTFILE, ">$outputfile" ) or die "Could not open output file: $! \n";
while (<FILE1>) {
if (/^(\d+)/) {
my $CC22 = $1;
while (<FILE2>) {
if (/^(\d+)\s+(\d+)\s+(\S+)/) {
my $CDS1 = $1;
my $CDS2 = $2;
my $CDS3 = $3;
if ( $CC22 > $CDS1 && $CC22 < $CDS2 ) {
print OUTPUTFILE "$CC22 $CDS1 $CDS2 $CDS3\n";
}
}
}
}
}
close(FILE1);
close(FILE2);
I have posted the same question on Perlmonks.
Because you are only reading FILE2 once it is only compared with the first line of FILE1
Subsequent lines are compared with the closed file
Stash the lines from FILE1 in an array and then compare each line in FILE2 with each array entry, as shown below
#!/usr/bin/perl
use strict;
use warnings;
my $outputfile = "out.txt";
open FILE1, "file1.txt"
or die "cannot open > CC22: $!";
open FILE2, "file2.txt"
or die "cannot open > CDS: $!";
open( OUTPUTFILE, ">$outputfile" ) or die "Could not open output file: $! \n";
my #file1list = ();
while (<FILE1>) {
if (/^(\d+)/) {
push #file1list, $1;
}
}
while (<FILE2>) {
if (/^(\d+)\s+(\d+)\s+(\S+)/) {
my $CDS1 = $1;
my $CDS2 = $2;
my $CDS3 = $3;
for my $CC22 (#file1list) {
if ( $CC22 > $CDS1 && $CC22 < $CDS2 ) {
print OUTPUTFILE "$CC22 $CDS1 $CDS2 $CDS3\n";
}
}
}
}
( there are also stylistic issues with the program (like capital letters for variables) but I've ignored these, it's quite a nice program for a beginner)
I thought I could simplify some of that by using split instead of regex, but I think my code is actually longer and more difficult to read! In any event, remember that split works great for problems like this:
# User config area
my $positions_file = 'input_positions.txt';
my $ranges_file = 'input_ranges.txt';
my $output_file = 'output_data.txt';
# Reading data
open my $positions_fh, "<", $positions_file;
open my $ranges_fh, "<", $ranges_file;
chomp( my #positions = <$positions_fh> );
# Store the range data in an array containing hash tables
my #range_data;
# to be used like $range_data[0] = {start => $start, end => $end, dir => $dir}
while (<$ranges_fh>) {
chomp;
my ( $start, $end, $dir ) = split; #splits $_ according to whitespace
push #range_data, { start => $start, end => $end, dir => $dir };
#print "start: $start, end: $end, direction: $dir\n";
} #/while
close $positions_fh;
close $ranges_fh;
# Data processing:
open my $output_fh, ">", $output_file;
#It feels like it should be more efficient to process one range at a time for all data points
foreach my $range (#range_data) { #start one range at a time
#each $range = $range_data[#] = { hash table }
foreach my $position (#positions) { #check all positions
if ( ( $range->{start} <= $position ) and ( $position <= $range->{end} ) ) {
my $output_string = "$position " . $range->{start} . " " . $range->{end} . " " . $range->{dir} . "\n";
print $output_fh $output_string;
} #/if
} #/foreach position
} #/foreach range
close $output_fh;
This code would probably run faster if the data processing was done during the while loop that's reading the range data.
Your bug was because you were embedding file processing, so your inner loop only went through the file's contents a single time and then was stuck at eof.
The easiest solution is just to load the inner loop file entirely into memory first.
The following demonstrates using more Modern Perl techniques:
#!/usr/bin/perl
use strict;
use warnings;
use autodie;
my $cc22file = "/Users/edwardtickle/Documents/CC22positions.txt";
my $cdsfile = "/Users/edwardtickle/Documents/CDSpositions.txt";
my $outfile = "/Users/edwardtickle/Documents/CC22CDS.txt";
my #ranges = do {
# open my $fh, '<', $cdsfile; # Using Fake Data instead below
open my $fh, '<', \ "517 1878 forward\n700 2500 forward\n2156 3289 forward\n99000 100000 forward\n22000 23000 backward\n";
map {[split]} <$fh>;
};
# open my $infh, '<', $cc22file; # Using Fake Data instead below
open my $infh, '<', \ "99269\n550\n100\n126477\n1700\n";
# open my $outfh, '>', $outfile; # Using STDOUT instead below
my $outfh = \*STDOUT;
CC22:
while (my $cc22 = <$infh>) {
chomp $cc22;
for my $cds (#ranges) {
if ($cc22 > $cds->[0] && $cc22 < $cds->[1]) {
print $outfh "$cc22 #$cds\n";
next CC22;
}
}
# warn "$cc22 No match found\n";
}
Outputs:
99269 99000 100000 forward
550 517 1878 forward
1700 517 1878 forward
Live Demo
i want to extract every 3rd number ( 42.034 , 41.630 , 40.158 as so on ) from the file
see example-
42.034 13.749 28.463 41.630 12.627 28.412 40.158 12.173 30.831 26.823
12.596 32.191 26.366 13.332 32.938 25.289 12.810 32.419 23.949 13.329
Any suggestions using perl script ?
Thanks,
dac
You can split file's contents to separate numbers and use the modulo operator to extract every 3rd number:
my $contents = do { local $/; open my $fh, "file" or die $!; <$fh> };
my #numbers = split /\s+/, $contents;
for (0..$#numbers) {
$_ % 3 == 0 and print "$numbers[$_]\n";
}
use strict;
use warnings;
use 5.010; ## for say
use List::MoreUtils qw/natatime/;
my #vals = qw/42.034 13.749 28.463 41.630 12.627 28.412 40.158 12.173 30.831
26.823 12.596 32.191 26.366 13.332 32.938 25.289 12.810 32.419 23.949 13.329/;
my $it = natatime 3, #vals;
say while (($_) = $it->());
This is probably the shortest way to specify that. If #list is your list of numbers
#list[ grep { $_ % 3 == 0 } 0..$#list ]
It's a one-liner!
$ perl -lane 'print for grep {++$i % 3 == 1} #F' /path/to/your/input
-n gives you line-by-line processing, -a autosplitting for field processing, and $i (effectively initialized to zero for our purposes) keeps count of the number of fields processed...
This method avoids reading the entire file into memory at once:
use strict;
my #queue;
while (<>) {
push #queue, / ( \d+ (?: \. \d* ) ? ) /gx;
while (#queue >= 3) {
my $third = (splice #queue, 0, 3)[2];
print $third, "\n"; # Or do whatever with it.
}
}
If the file has 10 numbers in every line you can use this:
perl -pe 's/([\d.]+) [\d.]+ [\d.]+/$1/g;' file
It's not a clean solution but it should "do the job".
Looks like this post lacked a solution that didn't read the whole file and used grep.
#!/usr/bin/perl -w
use strict;
my $re = qr/-?\d+(?:\.\d*)/; # Insert a more precise regexp here
my $n = 3;
my $count = 0;
while (<>) {
my #res = grep { not $count++ % $n } m/($re)/go;
print "#res\n";
};
I believe you’ll find that this work per spec, behaves politely, and never reads in more than it needs to.
#!/usr/bin/env perl
use 5.010_001;
use strict;
use autodie;
use warnings qw[ FATAL all ];
use open qw[ :std IO :utf8 ];
END { close STDOUT }
use Regexp::Common;
my $real_num_rx = $RE{num}{real};
my $left_edge_rx = qr{
(?: (?<= \A ) # or use \b
| (?<= \p{White_Space} ) # or use \D
)
}x;
my $right_edge_rx = qr{
(?= \z # or use \b
| \p{White_Space} # or use \D
)
}x;
my $a_number_rx = $left_edge_rx
. $real_num_rx
. $right_edge_rx
;
if (-t STDIN && #ARGV == 0) {
warn "$0: reading numbers from stdin,"
. " type ^D to end, ^C to kill\n";
}
$/ = " ";
my $count = 0;
while (<>) {
while (/($a_number_rx)/g) {
say $1 if $count++ % 3 == 0;
}
}
I have a source text in a file and looking for a code that would take the second (or n-th - in general) row from this file and print to a seperate file.
Any idea how to do this?
You can do this natively in Perl with the flip-flop operator and the special variable $. (used internally by ..), which contains the current line number:
# prints lines 3 to 8 inclusive from stdin:
while (<>)
{
print if 3 .. 8;
}
Or from the command line:
perl -wne'print if 3 .. 8' < filename.txt >> output.txt
You can also do this without Perl with: head -n3 filename.txt | tail -n1 >> output.txt
You could always:
Read all of the file in and but it into one variable.
Split the variable at the newline and store in an array
Write the value at the index 1 (for the second row) or the n-1 position to the separate file
use like this script.pl > outfile (or >> outfile for append)
this uses lexical filehandles and 3 arg open which are preferred to global filehandles and 2 arg open.
#!/usr/bin/perl
use strict;
use warnings;
use English qw( -no_match_vars );
use Carp qw( croak );
my ( $fn, $line_num ) = #ARGV;
open ( my $in_fh, '<', "$fn" ) or croak "Can't open '$fn': $OS_ERROR";
while ( my $line = <$in_fh> ) {
if ( $INPUT_LINE_NUMBER == $line_num ) {
print "$line";
}
}
note: $INPUT_LINE_NUMBER == $.
here's a slightly improved version that handles arbitrary amounts of line numbers and prints to a file.
script.pl <infile> <outfile> <num1> <num2> <num3> ...
#!/usr/bin/perl
use strict;
use warnings;
use English qw( -no_match_vars );
use Carp qw( croak );
use List::MoreUtils qw( any );
my ( $ifn, $ofn, #line_nums ) = #ARGV;
open ( my $in_fh , '<', "$ifn" ) or croak "can't open '$ifn': $OS_ERROR";
open ( my $out_fh, '>', "$ofn" ) or croak "can't open '$ofn': $OS_ERROR";
while ( my $line = <$in_fh> ) {
if ( any { $INPUT_LINE_NUMBER eq $_ } #line_nums ) {
print { $out_fh } "$line";
}
}
I think this will do what you want:
line_transfer_script.pl:
open(READFILE, "<file_to_read_from.txt");
open(WRITEFILE, ">File_to_write_to.txt");
my $line_to_print = $ARGV[0]; // you can set this to whatever you want, just pass the line you want transferred in as the first argument to the script
my $current_line_counter = 0;
while( my $current_line = <READFILE> ) {
if( $current_line_counter == $line_to_print ) {
print WRITEFILE $current_line;
}
$current_line_counter++;
}
close(WRITEFILE);
close(READFILE);
Then you'd call it like: perl line_transfer_script.pl 2 and that would write the 2nd line from file_to_read_from.txt into file_to_write_to.txt.
my $content = `tail -n +$line $input`;
open OUTPUT, ">$output" or die $!;
print OUTPUT $content;
close OUTPUT;
I want to print certain lines from a text file in Unix. The line numbers to be printed are listed in another text file (one on each line).
Is there a quick way to do this with Perl or a shell script?
Assuming the line numbers to be printed are sorted.
open my $fh, '<', 'line_numbers' or die $!;
my #ln = <$fh>;
open my $tx, '<', 'text_file' or die $!;
foreach my $ln (#ln) {
my $line;
do {
$line = <$tx>;
} until $. == $ln and defined $line;
print $line if defined $line;
}
$ cat numbers
1
4
6
$ cat file
one
two
three
four
five
six
seven
$ awk 'FNR==NR{num[$1];next}(FNR in num)' numbers file
one
four
six
You can avoid the limitations of the some of the other answers (requirements for sorted lines), simply by using eof within the context of a basic while(<>) block. That will tell you when you've stopped reading line numbers and started reading data. Note that you need to reset $. when the switch occurs.
# Usage: perl script.pl LINE_NUMS_FILE DATA_FILE
use strict;
use warnings;
my %keep;
my $reading_line_nums = 1;
while (<>){
if ($reading_line_nums){
chomp;
$keep{$_} = 1;
$reading_line_nums = $. = 0 if eof;
}
else {
print if exists $keep{$.};
}
}
cat -n foo | join foo2 - | cut -d" " -f2-
where foo is your file with lines to print and foo2 is your file of line numbers
Here is a way to do this in Perl without slurping anything so that the memory footprint of the program is independent of the sizes of both files (it does assume that the line numbers to be printed are sorted):
#!/usr/bin/perl
use strict; use warnings;
use autodie;
#ARGV == 2
or die "Supply src_file and filter_file as arguments\n";
my ($src_file, $filter_file) = #ARGV;
open my $src_h, '<', $src_file;
open my $filter_h, '<', $filter_file;
my $to_print = <$filter_h>;
while ( my $src_line = <$src_h> ) {
last unless defined $to_print;
if ( $. == $to_print ) {
print $src_line;
$to_print = <$filter_h>;
}
}
close $filter_h;
close $src_h;
Generate the source file:
C:\> perl -le "print for aa .. zz" > src
Generate the filter file:
C:\> perl -le "print for grep { rand > 0.75 } 1 .. 52" > filter
C:\> cat filter
4
6
10
12
13
19
23
24
28
44
49
50
Output:
C:\> f src filter
ad
af
aj
al
am
as
aw
ax
bb
br
bw
bx
To deal with an unsorted filter file, you can modified the while loop:
while ( my $src_line = <$src_h> ) {
last unless defined $to_print;
if ( $. > $to_print ) {
seek $src_h, 0, 0;
$. = 0;
}
if ( $. == $to_print ) {
print $src_line;
$to_print = <$filter_h>;
}
}
This would waste a lot of time if the contents of the filter file are fairly random because it would keep rewinding to the beginning of the source file. In that case, I would recommend using Tie::File.
I wouldn't do it this way with large files, but (untested):
open(my $fh1, "<", "line_number_file.txt") or die "Err: $!";
chomp(my #line_numbers = <$fh1>);
$_-- for #line_numbers;
close $fh1;
open(my $fh2, "<", "text_file.txt") or die "Err: $!";
my #lines = <$fh2>;
print #lines[#line_numbers];
close $fh2;
I'd do it like this:
#!/bin/bash
numbersfile=numbers
datafile=data
while read lineno < $numbersfile; do
sed -n "${lineno}p" datafile
done
Downside to my approach is that it will spawn a lot of processes so it will be slower than other options. It's infinitely more readable though.
This is a short solution using bash and sed
sed -n -e "$(cat num |sed 's/$/p/')" file
Where num is the file of numbers and file is the input file ( Tested on OS/X Snow leopard)
$ cat num
1
3
5
$ cat file
Line One
Line Two
Line Three
Line Four
Line Five
$ sed -n -e "$(cat num |sed 's/$/p/')" file
Line One
Line Three
Line Five
$ cat input
every
good
bird
does
fly
$ cat lines
2
4
$ perl -ne 'BEGIN{($a,$b) = `cat lines`} print if $.==$a .. $.==$b' input
good
bird
does
If that's too much for a one-liner, use
#! /usr/bin/perl
use warnings;
use strict;
sub start_stop {
my($path) = #_;
open my $fh, "<", $path
or die "$0: open $path: $!";
local $/;
return ($1,$2) if <$fh> =~ /\s*(\d+)\s*(\d+)/;
die "$0: $path: could not find start and stop line numbers";
}
my($start,$stop) = start_stop "lines";
while (<>) {
print if $. == $start .. $. == $stop;
}
Perl's magic open allows for creative possibilities such as
$ ./lines-between 'tac lines-between|'
print if $. == $start .. $. == $stop;
while (<>) {
Here is a way to do this using Tie::File:
#!/usr/bin/perl
use strict; use warnings;
use autodie;
use Tie::File;
#ARGV == 2
or die "Supply src_file and filter_file as arguments\n";
my ($src_file, $filter_file) = #ARGV;
tie my #source, 'Tie::File', $src_file, autochomp => 0
or die "Cannot tie source '$src_file': $!";
open my $filter_h, '<', $filter_file;
while ( my $to_print = <$filter_h> ) {
print $source[$to_print - 1];
}
close $filter_h;
untie #source;