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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40
votes
2answers
26k views

Getting “Not found” message when running a 32-bit binary on a 64-bit system

I have currently a strange problem on debian (wheezy/amd64). I have created a chroot to install a server (i can't give any more detail about it, sorry). Let's call its path /chr_path/. To make things ...
182
votes
5answers
372k 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 ...
17
votes
2answers
746 views

Security implications of running perl -ne '…' *

Apparently, running: perl -n -e 'some perl code' * Or find . ... -exec perl -n -e '...' {} + (same with -p instead of -n) Or perl -e 'some code using <>' * often found in one-liners ...
5
votes
4answers
19k views

compare two columns of different files and print if it matches

I am using solaris 10 and Grep options involving -f doesnt work . I have two pipe separated files: file1: abc|123|BNY|apple| cab|234|cyx|orange| def|kumar|pki|bird| file 2 : abc|123| ...
0
votes
1answer
1k views

/bin/sh: ./check-dependencies.pl: not found — but check-dependencies.pl exists!

I'm trying to build Moses, but when I run make I get the following output: minakshi@minakshi-Vostro-3500:~/Desktop/working-dir/moses/scripts$ make release # Compile the parts make all make[1]: ...
12
votes
7answers
11k views

How to insert the content of a file into another file before a pattern (marker)?

File1 contents: line1-file1 "1" line2-file1 "2" line3-file1 "3" line4-file1 "4" File2 contents: line1-file2 "25" line2-file2 "24" Pointer-file2 "23" ...
6
votes
1answer
185 views

How can I extract/change lines in a text file whose data are separated into fields?

How can I manipulate field-based data from the commandline? For example How can I print only lines whose Nth field is foo? How can I print only lines whose Nth field isn't foo? How can I print only ...
5
votes
1answer
1k 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 ...
7
votes
6answers
12k views

Repeat each line multiple times

Would like to have each line in a file repeated a fixed number of times. e.g. have each line repeated four times: a b c becomes: a a a a b b b b c c c c I've done some searching, and there are ...
8
votes
2answers
947 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 ...
3
votes
2answers
370 views

How to write this pseudocode where condition

This question is extension of this question about listing questions of directories. I get a problem that I need to understand the original section of the text. Current output where you see the ...
2
votes
5answers
281 views

Can the string “abcedf” be matched to string “bafcde” in a single line command?

I am planning to implement an indexing structure in my program. For example, if I have 100 rows in the table, I will number these rows from 1 to 100 in another column by appending an _ to the end of ...
6
votes
2answers
159 views

How exactly does perl's -0 option work?

According to man perlrun: -0[octal/hexadecimal] specifies the input record separator ($/) as an octal or hexadecimal number. If there are no digits, the null character is the ...
5
votes
3answers
5k 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 ...
4
votes
5answers
75 views

Count unique associated values in awk (or perl)

I've already found "How to print incremental count of occurrences of unique values in column 1", which is similar to my question, but the answer isn't sufficient for my purposes. First let me just ...
4
votes
4answers
3k views

Average rows with same first column

Given a file with two columns: Id ht 510 69 510 67 510 65 510 62 510 59 601 29 601 26 601 21 601 20 I need a way to coalesce all rows with the same ID into one that has an average height. In this ...
0
votes
4answers
235 views

How to sum up values of each two rows across their line in linux

I have a data like this: input.txt 1 0000100101000000 1 0000010100000000 2 1110000001000000 2 1111000000001000 3 0000000111111111 3 1111111100000000 4 8888345500000000 4 0000000000000000 and I ...
24
votes
3answers
18k 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 ${1+"$@"} ...
9
votes
6answers
3k 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
6k 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 ...
11
votes
4answers
3k 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?
8
votes
7answers
18k 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 ...
8
votes
2answers
528 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 ...
7
votes
2answers
401 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 ...
7
votes
1answer
2k 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
1k views

How to “grep” for line length in a given range?

NOTE: This question is the complement of this Q&A: How to grep for lines shorter or longer than specific thresholds? I need to get only the lines from a textfile (a wordlist, separated with ...
4
votes
4answers
2k views

merge 2 rows based on the same column values

I have a file like below. 47196436 47723284 name1 1.77273 42672249 52856963 name2 1.06061 52856963 430695 name2 1.16667 55094959 380983 name3 1.55613 17926380 55584836 name4 1.02461 3213456 34211 ...
6
votes
3answers
571 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 ...
6
votes
2answers
409 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
5answers
217 views

How to SED these paragraphs to MCQ format?

My data: Question Nr. 311 Main proteins are in the lorem ipsun A Lorem RNA test B Cells C Metoclom D Cells E Muscles Question Nr. 312 Main proteins are in the lorem ipsun A Lorem B Cells C ...
4
votes
5answers
459 views

How can I replace all semicolons after 1st one?

This problem is related to my attempt to import questions and their answers in a Excel file into .txt -file which Anki flashcard program handles as described here. I cannot have more than 2 fields so ...
4
votes
5answers
462 views

How to replace only the Nth occurrence of a pattern in a file?

How to replace the third occurrence of the string in the file using sed command. Example: Change only the third occurrence of is to us in the file. My input file contains: hai this is linux. hai ...
4
votes
1answer
92 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
117 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
5answers
3k views

Replacing text from a list of replacements. Added complication: backslashes

I have a file A that contains pairs of strings, one per line: \old1 \new1 \old2 \new2 ..... I would like to iterate over file A, and for each line perform the replacement (e.g. "\old1 -> \new1") ...
3
votes
4answers
205 views

To remove newlines after empty line

Data 4. Alendronic acid A. Antiosteoporotic agent. B. Inhibit osteoclast formation and function by inhibiting FPPS enzyme, so increase bone mass. C. Osteoporosis in combination with vitamin D. ...
3
votes
3answers
3k views

Replacing string in all files found by grep. Can't get it to work

I'm trying to do what title says. So I find all needed files with grep: grep --include=\*.{php,ini,conf,sh} -ril -P "'([\d\w\-\_\.]+)(@domain.com)'" '/var/www_data/somepath/' Now I assume it's ...
3
votes
10answers
3k views

Finding the maximum of the values in a file

I have a file which contains several numbers, as follows. 21 12 33 35 21 12 33 44 52 63 14 12 23 34 11 12 13 53 1 12 43 33 44 How can I find the maximum of these values, which is 63? I wanted to ...
2
votes
3answers
126 views

How can I delete everything between two markers in a file?

I have a text in a text file, where I want everything that is between strings like \{{[} and {]}\} to be deleted - including these strings themselves. These two string can lie on different lines as ...
2
votes
4answers
119 views

How to highlight given string in given place?

How can we modify this: <a href="http://foo.bar1">asfdlksafbar1qsasadf</a><br> <a href="http://foo.bar2">svasfbar2saldkfj</a><br> <a ...
2
votes
3answers
3k views

How to open terminal, split to 9 terminals and switch between them using one script?

I would like to open a terminal, split it to lets say 9 parts (3x3) and execute some bash script. But for each terminal part different script. Can this be done using perl, python or even bash? How ...
2
votes
4answers
322 views

Sed/awk/perl: reversing order of comma separated values, preserving other text

I have this text: LABEL1 .BYTE 01, 02, 03, 04, 05 .BYTE 01, 02, 03 I need to reverse only comma separated values order: LABEL1 .BYTE 05, 04, 03, 02, 01 .BYTE 03, 02, 01 I need ...
2
votes
1answer
75 views

How to write this replacement with condition

I want to replace now within my working directories the word -> with $\to$ if the word is not within verbatim environment. Pseudocode Replace all entriens of -> with $\to$ everywhere else but not ...
1
vote
1answer
287 views

How do I modify this Perl solution so that it will substitute embedded double quotes with single quotes?

Previously in this question: "string having doublequotes in between apart from the enclosing quotes" @BernieReiter asked a follow-up question where he wanted to take CSV entries such as the following: ...
0
votes
2answers
74 views

Find all characters “[1-777])” at the beginning of the line

Pseudocommand perl -pe 'g/^[1-777])/g' data.txt where I try to all numbers at the beginning of a line with ")" following them etc 1), 67) and 777). Data where all question numbers should (etc 1), ...
0
votes
2answers
229 views

How to pass arguments to perl when trying to change a line?

I am using the approach suggested in http://askubuntu.com/questions/434051/how-to-replace-a-string-on-the-5th-line-of-multiple-text-files to modify the first line of an archive. Let's suppose the ...
0
votes
2answers
90 views

To match only innermost environment by Regex

I want to match the innermost environment of begin{question} and its corresponding end{question}. Example data \section{Takayasu arteritis} \begin{question} {You get a patient. What do you notice ...
3
votes
1answer
155 views

How to print incremental count of occurrences of unique values in column 1

I'm trying to come up with an solution to this problem, I need to incrementally count and then print the counts of the unique values in column 1 of a tab delimited text file. Here is an example: ...
3
votes
2answers
1k views

case sensitive substitution; same target ids

I am struggled myself to make a case sensitive replacement in a text file. Please find below a segment of my sed file that I am running as sed -f file.sed < input.txt > output.txt ...
3
votes
1answer
825 views

How race conditions affect reads and writes (that happen at the same time)

Let's say I open a file a for reading. What if an application, let's call it aWriter writes to this file in random intervals. Are there any possibilities of me receiving improper file contents if I ...