I have a variable $string and i want to print all the lines after I find a keyword in the line (including the line with keyword)
$string=~ /apple /;
I'm using this regexp to find the key word but I do not how to print lines after this keyword.
It's not really clear where your data is coming from. Let's assume it's a string containing newlines. Let's start by splitting it into an array.
my #string = split /\n/, $string;
We can then use the flip-flop operator to decide which lines to print. I'm using \0 as a regex that is very unlikely to match any string (so, effectively, it's always false).
for (#string) {
say if /apple / .. /\0/;
}
Just keep a flag variable, set it to true when you see the string, print if the flag is true.
perl -ne 'print if $seen ||= /apple/'
If your data in scalar variable we can use several methods
Recommended method
($matching) = $string=~ /([^\n]*apple.+)/s;
print "$matching\n";
And there is another way to do it
$string=~ /[^\n]*apple.+/s;
print $&; #it will print the data which is match.
If you reading the data from file, try the following
while (<$fh>)
{
if(/apple/)
{
print <$fh>;
}
}
Or else try the following one liner
perl -ne 'print <> and exit if(/apple/);' file.txt
Related
Being a Perl newbie, please pardon me for asking this basic question.
I have a text file #server1 that shows a bunch of sentences (white space is the field separator) on many lines in the file.
I needed to match lines with my keyword, remove the same lines, and extract only the last field, so I have tried with:
my #allmatchedlines;
open(output1, "ssh user1#server1 cat /tmp/myfile.txt |");
while(<output1>) {
chomp;
#allmatchedlines = $_ if /mysearch/;
}
close(output1);
my #uniqmatchedline = split(/ /, #allmatchedlines);
my $lastfield = $uniqmatchedline[-1]\n";
print "$lastfield\n";
and it gives me the output showing:
1
I don't know why it's giving me just "1".
Could someone please explain why I'm getting "1" and how I can get the last field of the matched line correctly?
Thank you!
my #uniqmatchedline = split(/ /, #allmatchedlines);
You're getting "1" because split takes a scalar, not an array. An array in scalar context returns the number of elements.
You need to split on each individual line. Something like this:
my #uniqmatchedline = map { split(/ /, $_) } #allmatchedlines;
There are two issues with your code:
split is expecting a scalar value (string) to split on; if you are passing an array, it will convert the array to scalar (which is just the array length)
You did not have a way to remove same lines
To address these, the following code should work (not tested as no data):
my #allmatchedlines;
open(output1, "ssh user1#server1 cat /tmp/myfile.txt |");
while(<output1>) {
chomp;
#allmatchedlines = $_ if /mysearch/;
}
close(output1);
my %existing;
my #uniqmatchedline = grep !$existing{$_}++, #allmatchedlines; #this will return the unique lines
my #lastfields = map { ((split / /, $_)[-1]) . "\n" } #uniqmatchedline ; #this maps the last field in each line into an array
print for #lastfields;
Apart from two errors in the code, I find the statement "remove the same lines and extract only the last field" unclear. Once duplicate matching lines are removed, there may still be multiple distinct sentences with the pattern.
Until a clarification comes, here is code that picks the last field from the last such sentence.
use warnings 'all';
use strict;
use List::MoreUtils qw(uniq)
my $file = '/tmp/myfile.txt';
my $cmd = "ssh user1\#server1 cat $file";
open my $fh, '-|', $cmd // die "Error opening $cmd: $!"; # /
while (<$fh>) {
chomp;
push #allmatchedlines, $_ if /mysearch/;
}
close(output1);
my #unique_matched_lines = uniq #allmatchedlines;
my $lastfield = ( split ' ', $unique_matched_lines[-1] )[-1];
print $lastfield, "\n";
I changed to the three-argument open, with error checking. Recall that open for a process involves a fork and returns pid, so an "error" doesn't at all relate to what happened with the command itself. See open. (The # / merely turns off wrong syntax highlighting.) Also note that # under "..." indicates an array and thus need be escaped.
The (default) pattern ' ' used in split splits on any amount of whitespace. The regex / / turns off this behavior and splits on a single space. You most likely want to use ' '.
For more comments please see the original post below.
The statement #allmatchedlines = $_ if /mysearch/; on every iteration assigns to the array, overwriting whatever has been in it. So you end up with only the last line that matched mysearch. You want push #allmatchedlines, $_ ... to get all those lines.
Also, as shown in the answer by Justin Schell, split needs a scalar so it is taking the length of #allmatchedlines – which is 1 as explained above. You should have
my #words_in_matched_lines = map { split } #allmatchedlines;
When all this is straightened out, you'll have words in the array #uniqmatchedline and if that is the intention then its name is misleading.
To get unique elements of the array you can use the module List::MoreUtils
use List::MoreUtils qw(uniq);
my #unique_elems = uniq #whole_array;
I am an absolute beginner in perl and I am trying to extract lines of text between 2 strings on different lines but without success. It looks like I`m missing something in my code. The code should print out the file name and the found strings. Do you have any idea where could be the problem ? Many thanks indeed for your help or advice. Here is the example:
*****************
example:
START
new line 1
new line 2
new line 3
END
*****************
and my script:
use strict;
use warnings;
my $command0 = "";
opendir (DIR, "C:/Users/input/") or die "$!";
my #files = readdir DIR;
close DIR;
splice (#files,0,2);
open(MYOUTFILE, ">>output/output.txt");
foreach my $file (#files) {
open (CHECKBOOK, "input/$file")|| die "$!";
while ($record = <CHECKBOOK>) {
if (/\bstart\..\/bend\b/) {
print MYOUTFILE "$file;$_\n";
}
}
close(CHECKBOOK);
$command0 = "";
}
close(MYOUTFILE);
I suppose that you are trying to use a flip-flop here, which might work well for your input, but you've written it wrong:
if (/\bstart\..\/bend\b/) {
A flip-flop (the range operator) uses two statements, separated by either .. or .... What you want is two regexes joined with ..:
if (/\bSTART\b/ .. /\bEND\b/)
Of course, you also want to match the case (upper), or use the /i modifier to ignore case. You might even want to use beginning of line anchor ^ to only match at the beginning of a line, e.g.:
if (/^START\b/ .. /^END\b/)
You should also know that your entire program can be replaced with a one-liner, such as
perl -ne 'print if /^START\b/ .. /^END\b/' input/*
Alas, this only works for linux. The cmd shell in Windows does not glob, so you must do that manually:
perl -ne "BEGIN { #ARGV = map glob, #ARGV }; print if /^START\b/ .. /^END\b/" input/*
If you are having troubles with the whole file printing no matter what you do, I think the problem lies with your input file. So take a moment to study it and make sure it is what you think it is, for example:
perl -MData::Dumper -e"$Data::Dumper::Useqq = 1; print Dumper $_;" file.txt
If you're matching a multi-line string, you might need to tell the regexp about it:
if (/\bstart\..\/bend\b/s) {
note the s after the regex.
Perldoc says:
s
Treat string as single line. That is, change "." to match any
character whatsoever, even a newline, which normally it would not
match.
Suppose I have a file with these inputs:
line 1
line 2
line3
My program should only store "line1", "line2" and "line3" not the newlines. How do I achieve that?
My program already removed leading and trailing whitespaces but it doesn't help to remove newline.
I am setting $/ as \n because each input is separated by a \n.
while (<>) {
chomp;
next unless /\S/;
print "$_\n";
}
Set
$/ = q(); # that's an empty string, like "" or ''
while (<>) {
chomp;
...
}
The special value of the defined empty string is how you tell the input operator to treat one or more newlines as the terminator (preferring more), and also to get chomp to remove them all. That way each record always starts with real data.
Perl -n is the equivalent of wrapping while(<>) { } around your script. Assuming that all you need to do is eliminate blank lines, you can do it like this:
#! /usr/bin/perl -n
print unless ( /^$/ );
... On the other hand, if that's all you need to do, you might as well ditch perl and use
grep -n '^$'
Edit: your post says that you want to store values where lines are not blank... in that case, assuming that you don't have too much work to do in the rest of your script, you might do something like this:
#! /usr/bin/perl -n
my #values;
push #values, $_ unless ( /^$/ );
END {
# do whatever work you want to do here
}
... but this quickly reaches a point of limiting returns if you have very much code inside the END{} block.
I am writing a perl program to extract lines that are in between the two patterns i am matching. for example the below text file has 6 lines. I am matching load balancer and end. I want to get the 4 lines that are in between.
**load balancer**
new
old
good
bad
**end**
My question is how do you extract lines in between load balancer and end into an array. Any help is greatly appreciated.
You can use the flip-flop operator to tell you when you are between the markers. It will also include the actual markers, so you'll need to except them from the data collection.
Note that this will mash together all the records if you have several, so if you do you need to store and reset #array somehow.
use strict;
use warnings;
my #array;
while (<DATA>) {
if (/^load balancer$/ .. /^end$/) {
push #array, $_ unless /^(load balancer|end)$/;
}
}
print #array;
__DATA__
load balancer
new
old
good
bad
end
You can use the flip-flop operator.
Additionally, you can also use the return value of the flipflop to filter out the boundary lines. The return value is a sequence number (starting with 1) and the last number has the string E0 appended to it.
# Define the marker regexes separately, cuz they're ugly and it's easier
# to read them outside the logic of the loop.
my $start_marker = qr{^ \s* \*\*load \s balancer\*\* \s* $}x;
my $end_marker = qr{^ \s* \*\*end\*\* \s* $}x;
while( <DATA> ) {
# False until the first regex is true.
# Then it's true until the second regex is true.
next unless my $range = /$start_marker/ .. /$end_marker/;
# Flip-flop likes to work with $_, but it's bad form to
# continue to use $_
my $line = $_;
print $line if $range !~ /^1$|E/;
}
__END__
foo
bar
**load balancer**
new
old
good
bad
**end**
baz
biff
Outputs:
new
old
good
bad
If you prefer a command line variation:
perl -ne 'print if m{\*load balancer\*}..m{\*end\*} and !m{\*load|\*end}' file
For files like this, I often use a change in the Record Separator ( $/ or $RS from English )
use English qw<$RS>;
local $RS = "\nend\n";
my $record = <$open_handle>;
When you chomp it, you get rid of that line.
chomp( $record );
I have one string of line like
comments:[I#1278327] is related to office communicator.i fixed the bug to declare it null at first time.
Here I am searching index of I#then I want the whole word means [I#1278327]. I'm doing it like this:
open(READ1,"<letter.txt");
while(<READ1>)
{
if(index($_,"I#")!=-1)
{
$indexof=index($_,"I#");
print $indexof,"\n";
$string=substr($_,$indexof);##i m cutting that string first from index of I# to end then...
$string=substr($string,0,index($string," "));
$lengthof=length($string);
print $lengthof,"\n";
print $string,"\n";
print $_,"\n";
}
}
Is any API is there in perl to find the word length directly after finding the index of I# in that line.
You could do something like:
$indexof=index($_,"I#");
$index2 = index($_,' ',$indexof);
$lengthof = $index2 - $indexof;
However, the bigger issue is you are using Perl as if it were BASIC. A more perlish approach to the task of printing selected lines:
use strict;
use warnings;
open my $read, '<', 'letter.txt'; # safer version of open
LINE:
while (<$read>) {
print "$1 - $_" if (/(I#.*?) /);
}
I would use a regex instead, a regex will allow you to match a pattern ("I#") and also capture other data from the string:
$_ =~ m/I#(\d+)/;
The line above will match and set $1 to the number.
See perldoc perlre