Perl is a high-level, general-purpose, interpreted, dynamic programming language. It was originally developed by Larry Wall as a general-purpose Unix scripting language to make report processing easier, over a period with support from open source community, it has evolved and matured to be used for ...

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16
votes
2answers
7k views

What does ${1+“$@”} mean in a shell script, and how does it differ from “$@”?

In the Perl documentation, perlrun(1) suggests launching Perl scripts using a bilingual shell/Perl header: #!/bin/sh #! -*-perl-*- eval 'exec perl -x -wS $0 ${1+"$@"}' if 0; What does ${1+"$@"} ...
10
votes
4answers
1k views

Why is Perl installed by default with most Linux distributions?

Just curious. The title says it all: Why is Perl installed by default with most Linux distributions?
10
votes
2answers
110 views

Resource friendly way to indicate to user program is not hanging

I have a Perl script on a *nix system which, at one point, is processing 50,000 + lines of text. This takes some time. I am trying to find a resource friendly way to let the user know the program is ...
9
votes
6answers
338 views

Using Perl to count the number of scientific numbers in a file

How I can count the number of scientific numbers in a file? The file also has a few lines of header which needs to be skipped. A portion of the file's content is in below. FileHeaderLine1 ...
9
votes
2answers
5k views

How to know reason of a process going to sleep state and wake it up?

When I do 'top' , I see my perl script process in 'S' state. Is there a way to know, what is making this perl process go in sleep state and ways to wake it up? Any way to debug to give more insights ...
8
votes
6answers
2k views

Delete lines beginning with #

How do I delete lines beginning with a #, given that there can be whitespace on the left and right of the #? # Master socket provides access to userdb information. It's typically
7
votes
6answers
2k views

Is there any alternative to grep's -A -B -C switches (to print few lines before and after )?

grep -A 2 -B 3 prints 2 lines after the grep string and prints 3 lines before. grep -C 3 prints 3 Lines before and 3 lines after Unfortunately, the grep I'm using does not support these ...
7
votes
2answers
180 views

Using empty line as context “group-separator” for grep

I need grep output with context, in color, and blank lines as group separator. In this question, I learned how to define custom group-separator, and I have constructed my grep command like this: grep ...
7
votes
4answers
2k views

Find files with same name but different content?

I want to generate a list of files that have: Same name Different content in a directory (including all children directories and content). How to do? Bash, perl, anything is fine. So, two ...
7
votes
1answer
331 views

Is there a way to make perl -i not clobber symlinks?

A friend of mine points out that if you do: perl -pi.bak -e 's/foo/bar/' somefile when "somefile" is actually a symlink, perl does just what the docs say it will do: It does this by renaming ...
6
votes
4answers
2k views

How to remove multiple blank lines from a file?

I have some text-files I use to take notes in - just plain text, usually just using cat >> file. Occasionally I use a blank line or two (just return - the new-line character) to specify a new ...
6
votes
2answers
130 views

Sorting with Perl respecting Locale Settings

Following data needs to be sorted respecting the locale sort order: wird sin wär pêche war Über Uber péché peach There was nor problem by using sort $ sort < data peach pêche péché sin Uber ...
6
votes
3answers
6k views

How can I install perldoc on Ubuntu?

Ubuntu 10.10 comes with Perl 5.10.1 pre-installed, but strangely enough perldoc isn't part of the package. $ perldoc You need to install the perl-doc package to use this program. How can I make ...
6
votes
1answer
791 views

How can I replace a string in a file(s)?

Replacing strings in files based on certain search criteria is a very common task. How can I replace string foo with bar in all files in the current directory? do the same recursively for sub ...
6
votes
2answers
534 views

Special character '#' in Perl SSH command

I try to send command using SSH in my perl script with # but it gets truncated right at # Example: Input text is : $message = "Product ID # STK000134" The SSH command is : $execute=`ssh -q ...
6
votes
4answers
8k views

invalid SSL_version specified at /usr/share/perl5/IO/Socket/SSL.pm line 332

Since I upgraded my PC from (k)ubuntu 12.04 to 12.10 I receive this error message when trying to send an email using sendemail. Installing an older version of IO::Socket::SSL is not an option. I ...
6
votes
3answers
161 views

What is the difference between invoking a perl script via sh or perl

I have a simple Hello World perl script. #!/usr/bin/perl print 'Hello world.'; It works fine if I run it via perl <file_name>, but it fails I run it via sh <file_name>. My ...
5
votes
3answers
509 views

Is there a perl or awk solution for this problem?

I have an input file (input.txt) like below. id1 id2 name weight 53723848 12651711 timburnes 1.36667 53530214 12651711 timburnes 1.51191 53723848 53530214 timburnes 1.94 764157 ...
5
votes
2answers
2k views

Replacing missing value blank space with zero

I have input.txt tab-delimited text file around 30K lines, I would like to check each row (s1..s30K lines) for missing value (i.e blank space) and fill the missing value with zero value.See out.txt ...
5
votes
1answer
175 views

Execute a command within 'sed'

I have a list of random memory addresses saved in a text file, and I need to sed them out, decode them, and save them back to my file. However, the decoding operation I'm trying to perform is handled ...
5
votes
1answer
3k views

Execute Nohup command with input

In UNIX, I have a process that I want to run using nohup. However this process will at some point wait at a prompt where I have to enter yes or no for it to continue. So far, in UNIX I have been doing ...
5
votes
3answers
1k views

Regex & Sed/Perl: Match word that ISN'T preceded by another word

I'd like to use sed or perl to replace all occurrences of a word that doesn't have a certain word in front of it. For example, I have a text file that contains a plot of a movie and I want to replace ...
5
votes
2answers
960 views

Remove unknown unicode character from textfiles - sed, other bash/shell methods

I need to search and replace all occurences of an unknown character in some files having the same name. Opening such files with vi, I read <91> code for that character. Opening them with nano, I ...
5
votes
2answers
184 views

Getting or cloning the users current terminal?

I have to work with a script that forks and launches an instance of xterm in order to display log output in one window and have an interactive interface in the other. Personally I prefer rxvt-unicode ...
5
votes
3answers
3k views

How to filter IPv4 and IPv6 addresses?

echo "1.1.1.1" | awk '/[0-9]*\.[0-9]*\.[0-9]*\.[0-9]*/ {print $1}' How can I filter IPv4 addresses in a script, and how can I filter IPv6 addresses. I mean more precisely then this so the oneliner ...
5
votes
1answer
35 views

Count duplicate rows with constraint

I have the following file: A B 1990 A C 2001 A C 2013 A B 2001 B C 2013 A D 2001 A D 2014 I need to count duplicate pairs (in the 1st and 2nd column) and to each such pair assign the lowest value ...
4
votes
7answers
318 views

How can I groups numbers in a file

I have a file with numbers in float format. I can review them via sort -rn numbers.txt | less I would like though to be able to "group" them. I.e. easily see how many are in the same range. To give an ...
4
votes
5answers
3k views

extract the 4th column from a csv file using unix command

I have a csv file formatted as below. "col1","col2","col3","col4" "1","text1","<p>big html text</p> ","4th column" "2","text2","<p>big2 html2 text2</p> ...
4
votes
2answers
1k views

How do you determine if AIX 5.3 has PERL installed?

Simply put, how do you determine if AIX 5.3 has PERL installed as non-root?
4
votes
6answers
98 views

Only show the lines that are in all textfiles at least once

a.txt cat a.txt a b x c b.txt cat b.txt d e a f the q: SOMEMAGICK *.txt a Q: how can I show only the lines that are in all *.txt files?
4
votes
2answers
251 views

How is the inplace modification of a file being done?

What does the "inplace" modification of a file e.g. via sed -i or perl -i mean? My question is about how this inplace modification is done. Is the file copied the modification is done in the copy and ...
4
votes
2answers
127 views

run perl script with unknown perl location

I'm developing a perl script which expected to be downloaded by Mac users with a very small knowledge of shell, linux etc, let's say office managers and accountants. After the downloading the script ...
4
votes
2answers
6k views

Compare two file columns

I have long text files with space-delimited fields: cat file1.txt Id leng sal mon 25671 34343 56565 5565 44888 56565 45554 6868 23343 23423 26226 6224 77765 88688 87464 6848 66776 23343 63463 ...
4
votes
4answers
163 views

Howto find and move a text line inside a file?

I need to change a text line position inside a file; from one line position to another one, underneath a defined text. For example, I have the following text block (on /etc/pam.d/system-auth file) ...
4
votes
4answers
105 views

How to switch the first letters of two words?

$ echo 'foo bar' | sed SOMEMAGIC boo far $ echo 'one two' | sed SOMEMAGIC tne owo Q: in general, how can I replace the "b" from the "bar" to the "f" of the "foo"? And in reverse too, replace the "f" ...
4
votes
2answers
326 views

Replace string with sequential index

Can someone suggest an elegant way to accomplish this? Input: test instant () test instant () ... test instant () //total 1000 lines output should be: test instant1 () test ...
4
votes
2answers
133 views

Column mismatch and substituting

input.txt (tab-delimted) TTTTOTTT00000000008 RTTTT899 5.00E-28 TTTTOTTT00000000046 RTTTWRR 3.00E-31 TTTTOTTT00000000051 2.00E-11 TTTTOTTT00000000051 7.00E-12 TTTTOTTT00000000054 ...
4
votes
2answers
644 views

Installing CPAN dists not in the Arch repos

There's a lot of CPAN distributions in the Arch repositories, but not all of them. How should I handle a situation when I need a dist that is not already in the repos? Should I use the cpan program ...
4
votes
4answers
947 views

How can I remove a specific string from a file only if there are other lines in the file?

How can I remove a specific string from a file ONLY if there are other lines in the file? For example, don't touch this file: cat file.txt ASDF but remove "ASDF" from this file: cat file.txt ASDF ...
4
votes
2answers
66 views

Get the maximum sum for a file on 2 keys

I have a file as below. key1 key2 key3 a1 2 l1 a1 2.5 l2 a2 2 l2 a3 2.5 l3 a3 2.1 l4 a3 2.2 l5 I am trying to find the maximum possible sum of key2 that satisfies the ...
4
votes
1answer
435 views

Using Modifiers of Perl-compatible Regex (PCRE) in grep

According to grep --help and man grep, we can use the -P option in order to interpret the pattern as a Perl regular expression (PCRE, to be precise), instead of the default POSIX basic regular ...
4
votes
2answers
224 views

Trying to do arithmetic in Perl rename tool (Debian)

Supposed I have five mp3 files: 01-trackfoo.mp3 02-trackbar.mp3 03-trackbaz.mp3 04-trackabc.mp3 05-trackxyz.mp3 Now I give a quick listen to the files (just mplayer on console will do the trick) ...
4
votes
3answers
2k views

Help with piped program in sendmail's /etc/aliases

I'm trying some sort of auto-subscription via a homegrown script. I know it can be achieved by mailing lists such as Mailman but I also want to learn at the same time on how to do it by hand. Here's ...
4
votes
1answer
874 views

Renaming files to have lower case extensions with 'rename'

I'm trying to currently rename a large set of files and have been using quite kludgy methods to do so, such as: rename 's:(.*)\.MOV:$1.mov:g' *.MOV rename 's:(.*)\.JPG:$1.jpg:g' *.JPG What I'd ...
4
votes
2answers
58 views

Using perl to modify a LaTeX document

I am trying to use perl in order to modify a LaTeX document. In fact, I am trying to change the citation format from for example: . \cite{poelma20113d} to \cite{poelma20113d}. In other words, I ...
4
votes
1answer
63 views

Regex this question format into LaTeX

1. Lorem ipsun la la la? 1. Sopor 2. Stupor 3. Torpor 2. A patient has Lorem? 1. Sopor 2. Stupor 3. Somnolentia 4. La 5. Coma 3. Doesn't Response to strong external irritants is short. Tendon, ...
4
votes
6answers
345 views

What is the easiest way to check if column A and B values goes both ways with AWK? [closed]

What is the easiest way to check if column A and B values goes both ways? Output to check: Mike John John Mike Pamela Barbara Barbara Pamela Mike Paul Roger Paul Desired output Mike <-> ...
4
votes
1answer
255 views

Passing clicked links in rxvt to a script

I start my browser vimprobable in tabbed like so: "`tabbed -d > /tmp/tabbed.xid`; vimprobable2 -e `cat /tmp/tabbed.xid`" [1] I am then able to send all new instances of vimprobable to tabbed (and ...
4
votes
2answers
56 views

Verify line endings from a text created by perl script

I am interested in seeing the contents of a text file in hex mode. I have tried :%!xxd and the problem is that I can not really understand which hex code represents each letter e.g. when you use an ...
4
votes
1answer
98 views

Is building Perl an inside joke or is it supposed to require this many `make` invocations?

So I am building Perl version 5.18.2 from source on an ARMv7 processor right now, a Krait on the Snapdragon S4, and I am not too sure how much support there is for such an architecture. By the way, I ...