grep is a command-line tool for searching text patterns in files

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Average rows with same first column

Given a file with two columns: Id ht 510 69 510 67 510 65 5l0 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 ...
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1answer
156 views

grep for n or more periods on a given line

I want to be able to arbitrarily match lines that contain a lot of periods, like this: $ echo "there's. someone on the wing. some. thing." | grep -stuFF [[:idunno:]]{4,} there's. someone on the wing. ...
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Display lines inbetween text with grep

I know that I can use the -A and -B command for grep to get a lot of what I am looking for however that is not quite what I want. I am looking to parse the httpd.conf file to search for a domain. ...
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cut / grep and df -h

How can I grep or cut the "173G" under "Verf"? I need this for Unix scripting in school. jonas@jonaspc:~/$ df -h /dev/sda2 Dateisystem Größe Benutzt Verf. Verw% Eingehängt auf /dev/sda2 ...
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814 views

Extracting text from a text file in bash

I have a large text file that is all one line. In the text are several sections that looks like foo=12345 and I need to extract them all as separate lines, ignoring the rest of the file. For ...
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2answers
940 views

How to search for a string only in textfiles? (recursively)

I can list all the textfiles (by mimetype) in a folder with: find . -type f -print0 | xargs -0 file -i | fgrep -i text | sed 's/:$//g' 2>/dev/null | awk 'BEGIN {FS=": "} {print $1}' Ok. But how ...
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996 views

extract only the substring after double quotes - grep

I have a file which is as below. <a href="http://firstlink.com" title="title1"> <a href="http://secondlink.com" title="title2"> <a href="http://thirdlink.com" title="title3"> <a ...
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60 views

How to separate numerical values from identifiers

I'm currently writing a shell script that seperate values from their identifiers (retrieved from grep). For example, if I grep a certain file I will retrieve the following information: value1 = 1 ...
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How do I use tee to redirect to grep

I don't have much experience of using tee, so I hope this is not very basic. After viewing one of the answers to this question I came across a strange beheviour with tee. In order for me to output ...
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923 views

What is the best way to find a list of several strings within a large text file

The short, general question is: In Unix/Linux, what is the best way to find a list of several (about 150) strings within a large text file? I am asking this to all Unix/Linux experts as a general ...
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Filtering on dates with grep and awk

I have created the alias below in my .bash_aliases file alias auth="grep \"$(date|awk '{print $2,$3}')\" /var/log/auth.log | grep -E '(BREAK-IN|Invalid user|Failed|refused|su|Illegal)'" ...
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254 views

Strings enclosed in '' are ignored when using grep

When I tried searching for a string within a file, the results didn't include those that were enclosed in single quotes. For example: grep -rn text folder/ The results didn't include strings the ...
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158 views

find/grep outputs two lines for each file it finds match

I search my code base to find string patterns and list all the files where the pattern is found but only the file and not the lines on which it is found: find . -name *.java -exec grep -l 'someText' ...
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134 views

Why does grep treat '[D]ebug' string differently?

I've created simple text file named "T" to test the unusual behavior of grep: 1 Debug 2 debug 3 determined 4 Determined Tried different syntax: $ grep De T 1 Debug ...
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105 views

Can someone clarify this Bash script

I'm learning something about Bash scripting, and I came across this example: The task is to write a Bash script that reads a file, given with the first argument, pulls out those records that have the ...
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866 views

How can I grep for this or that (2 things) in a file?

I have a file that has "then"'s and "there"'s. I can $ grep "then " x.x x and then some x and then some x and then some x and then some and I can $ grep "there " x.x If there is no blob none ...
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197 views

Understanding grep --label=

I am looking for an explanation how grep --label=LABEL works: Maybe somebody can give me an example [or two] on what --label= is for. I understand what grep and zgrep are supposed to do – the ...
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grep to find “print” not “#print”

In debugging, I use a lot of 'print' and commenting out it with '#print'. How can I use grep to find the line without '#' before 'print'? # print <- not detect #print <- not detect abc # print ...
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Why does grep not work with redirection?

Using the top command with redirection works fine: top > top.log Now I want to use grep to filter a certain line: top | grep "my_program" > top.log But the log file will remain empty. But ...
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324 views

Grep one liner to remove blocks of random text

Using a script to backup some Cisco routers and compare startup and running configs. My output is tarnished by some ssl certificates it returns - I wish to remove them. Given: ********* ERROR ...
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1answer
957 views

git grep colors differ from grep custom colors

I've setup grep colors in my ~/.bashrc : export GREP_COLORS='ms=01;34:mc=01;34:sl=:cx=:fn=35:ln=32:bn=32:se=36' They work for grep --color=auto grep --color=always Unfortunately, those custom ...
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419 views

How to trick an init script into returning 0

I have a init script which is poorly designed because it does not conform to the Linux Standard Base Specifications The following should have an exit code of 0 if running, and 3 if not running ...
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130 views

Can I make grep treat escaped multiline as a single line?

How can I make tools like grep treat multilines escaped with a backslash as a long single line? Let's say I have some files that looks like this: testvar=test1 \ test2 \ test3 ...
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Please explain the -f option in pgrep

man pgrep says the following about -f option: -f The pattern is normally only matched against the process name. When -f is set, the full command line is used. What does it ...
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691 views

Longest common substring using grep

I have a huge text file called dictionary.txt with entries like ABC_SEQ_NUM This represents.... ABC_RANK This represents.... ABC_BSC_ID This represents... PQR_TA_DATE_AF This ...
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grep and escaping a dollar sign

I want to know which files have the string $Id$. grep \$Id\$ my_dir/mylist_of_files returns 0 occurrences. I discovered that I have to use grep \$Id$ my_dir/mylist_of_files Then I see that the ...
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520 views

grep and brackets in text

I store downloaded files in a log like this: [source] filename To avoid downloading a file more than once I grep for [source] filename before: if ! grep "$signature" downloaded.log > ...
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98 views

Is there any drawback to using “grep -E” instead of plain “grep”?

I understand that GNU grep without -E uses basic regex and that grep -E uses extended regex. Is there any harm in using grep -E even for situations that would work with plain grep?
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144 views

How much text does grep/egrep consume each time?

I'm confused on grep/egrep. These tools match a single line I think? In some cases I have heard "logical" line. Questions Is it correct to assume that essentially grep/egrep always processes a ...
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284 views

Grep command in shell script

I've been writing a shell script which should make grep command outputs for further use. However when I pass a variable containing ~/.../multiple_dir/* to grep as input I get empty output file. ...
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41 views

Extracting just a single group from a regular expression

I am trying to get a list of numbers from some hacked-together log files using zgrep. So, I am using: zgrep -ie "total time: .* ms" * This returns the whole line that I care about. I'd just like ...
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Get all regex matches between two patterns and print them to file

I've got a file with a bunch of long lines. I'd like to grab every group between two patterns and print them to a new file, one match per line. I could manage to do this with Python, but I'd prefer ...
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890 views

Optimizing a shell script with long running while loop

I have written a shell script which has to do the following: Capture session commands into one file. Every individual command into separate file. Mail every individual command file content based on ...
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324 views

Speed up zgrep on a multi-core computer

I'm running zgrep on a computer with 16 CPUs, but it only takes one CPU to run the task. Can I speed it up, perhaps utilize all 16 cores? P.S The IO is just fine, I could just copy the gzipped file ...
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191 views

How to grep recursively in order of last modified time?

grep -r does a recursive search in all files in a particular directory. However, if I want these files to be read by grep in the order of their last modified time, how do I do that?
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Grep: search and replace full line

The command grep "foo" myfile.txt prints all matching lines in my file. Now I want to replace the full line with another string. How can I do that?
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how to grep complex hierarcy?

I have a file as:- start apple 1 a 2 b 3 c start orange 4 a 5 b start mango 1 a start a/b/c 5 z end 4 b end 6 c end start banana 3 c end 4 d 5 e end I want the output as :- 1 apple/a 2 apple/b 3 ...
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84 views

pcregrep newline lookbehind assertion bug?

Attempting to use pcregrep to print the first line after a blank line. For example, contents of file first line second line I need second line to be printed. Here are a few tests using the same ...
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99 views

What's the difference between \b and \< in the grep command

In the man page of grep, I see The symbols \< and \> respectively match the empty string at the beginning and end of a word. The symbol \b matches the empty string at the edge of a ...
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335 views

grep string from contents of file command then delete file

I have a peculiar problem I need help with. I have a large batch of .docx files where a certain number of them are junk. I know how to identify these files from the file command, as they contain the ...
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804 views

test if return true if grep on output has string in one line

I just want to return true or false if a service is running. Here is where I'm at, not first try or last but current at writing: service iptables status | grep -qi "not running" The sdtout for ...
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131 views

Grep perl syntax and copyright character

I am trying to pull some links out of text that I downloaded of off the internet using grep, but keep getting "Aborted (core dumped)". When using grep I tend to use -P as I prefer to use perl syntax ...
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385 views

Print non-existent files from a pipe input

I have a directory of lots of .PDF and .JPG files. There should be a .JPG file for each .PDF with the same name. I'm trying to use a command to find .PDF files that doesn't have a .JPG file. My ...
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1answer
256 views

grep list of names and information from bigger file

I have two files: one with list of names (500 entries) and other having some more information for each entry in A.txt and extra entries too. File A.txt (each line is starting with > (fasta format) ...
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Search string in many files on HP-UX

I need to find which files (they can have space in the filename) of a directory contains a string using only sh and system's commands (Perl is not an option). For a few files, this command works ...
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How to use a value returned by a script in grep filter?

I'm on FreeBSD's csh. I want to form a row with domains of one user and then use this row to filter exim maillog to get only mail from/to this user's domains. I wrote a script to form a row from a ...
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Using grep/sed/awk to classify log file entries

I need to process a very large log file with many lines in different formats. My goal is to extract unique line entries who have the same starting pattern, e.g. '^2011-02-21.*MyKeyword.*Error', ...
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How do I check if a file already has line with “contents” in it?

I need to know if a file aready has line with contents X in it, if not append line. here's the code I've tried. if ! $(grep 'eval $(perl -I$HOME/foo/lib/perl5 -Mlocal::lib=$HOME/foo)' ~/.bashrc) then ...
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31 views

Matching several patterns on one line

I often use a program called tty0tty, which creates a null modem using PTYs. Now I want to make it part of an automated process. When I start tty0tty it prints (/dev/pts/1) <=> (/dev/pts/2) ...
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115 views

How can I open a file that results from grep?

I often grep a bunch of files to find a line, and then grep returns one result. Rather than copying and pasting the filename into a new command, I'd like to be able to open that one result with an ...