Questions tagged [grep]

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

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75
votes
2answers
260k views

How can I assign the output of a command to a shell variable?

I want to assign the result of an expression to a variable and concatenate it with a string, then echo it. Here's what I've got: #!/bin/bash cd ~/Desktop; thefile= ls -t -U | grep -m 1 "Screen Shot"; ...
120
votes
11answers
40k views

Convince grep to output all lines, not just those with matches

Say I have the following file: $ cat test test line 1 test line 2 line without the search word another line without it test line 3 with two test words test line 4 By default, grep returns each line ...
85
votes
8answers
173k views

How to run grep with multiple AND patterns?

I would like to get the multi pattern match with implicit AND between patterns, i.e. equivalent to running several greps in a sequence: grep pattern1 | grep pattern2 | ... So how to convert it to ...
298
votes
14answers
164k views

How can I prevent 'grep' from showing up in ps results?

When I search for some process that doesn't exist, e.g. $ ps aux | grep fnord wayne 15745 0.0 0.0 13580 928 pts/6 S+ 03:58 0:00 grep fnord Obviously I don't ...
54
votes
11answers
18k views

Is there a way to modify a file in-place?

I have a fairly large file (35Gb), and I would like to filter this file in situ (i.e. I don't have enough disk space for another file), specifically I want to grep and ignore some patterns — is there ...
15
votes
2answers
6k views

Print lines between (and including) two patterns

I want to start grepping from the lines that has CK at the end of line and stop grepping when the line has D at the end. I tried grep "$CK" "$D" file..txt, but it didn't work. Input: kkkkkkkkkkk ...
16
votes
6answers
15k views

How do I recursively grep through compressed archives?

I'm trying to find out what modules use Test::Version in cpan. So I've used minicpan to mirror it. My problem is that I need to iterate through the archives that are downloaded, and grep the files ...
26
votes
5answers
53k views

Multiline pattern match using sed, awk or grep [duplicate]

Is it possible to do a multiline pattern match using sed, awk or grep? Take for example, I would like to get all the lines between { and } So it should be able to match 1. {} 2. {.....} 3. {........
24
votes
5answers
35k views

How to grep for text in a file and display the paragraph that has the text?

Below is the text in the file: Pseudo name=Apple Code=42B state=fault Pseudo name=Prance Code=43B state=good I need to grep for "42B" and get the output from the above text like: Pseudo name=...
12
votes
2answers
3k views

grep - why do brackets in grep pattern remove the grep process from ps results?

Why do brackets in a grep pattern remove the grep process from ps results? $ ps -ef | grep XXXX [...] XXXX [...] grep XXXX $ ps -ef | grep [X]XXX [...] XXXX
69
votes
4answers
243k views

Recursive grep vs find / -type f -exec grep {} \; Which is more efficient/faster?

Which is more efficient for finding which files in an entire filesystem contain a string: recursive grep or find with grep in an exec statement? I assume find would be more efficient because you can ...
74
votes
10answers
61k views

How to grep standard error stream (stderr)?

I am using ffmpeg to get the meta info of an audio clip. But I am unable to grep it. $ ffmpeg -i 01-Daemon.mp3 |grep -i Duration FFmpeg version SVN-r15261, Copyright (c) 2000-2008 Fabrice ...
25
votes
8answers
23k views

How to grep-inverse-match and exclude “before” and “after” lines

Consider a text file with the following entries: aaa bbb ccc ddd eee fff ggg hhh iii Given a pattern (e.g. fff), I would like to grep the file above to get in the output: all_lines except (...
280
votes
8answers
288k views

Can grep output only specified groupings that match?

Say I have a file: # file: 'test.txt' foobar bash 1 bash foobar happy foobar I only want to know what words appear after "foobar", so I can use this regex: "foobar \(\w\+\)" The parenthesis ...
134
votes
14answers
95k views

How can I grep in PDF files?

Is there a way to search pdf files using the power of grep, without converting to text first in Ubuntu?
129
votes
5answers
351k views

Can grep return true/false or are there alternative methods

As a part of this script, I need to be able to check if the first argument given matches the first word of file. If it does, exit with an error message; if it doesn't, append the arguments to the file....
13
votes
2answers
12k views

How do regular expressions differ from wildcards used to filter files

While we use * to denote zero or more previous characters in grep, we use *.c to find all C files when we use it with the ls command like ls *.c. Could someone tell how the use of * differs in these ...
17
votes
4answers
34k views

Output to stdout and at the same time grep into a file

I have a script that outputs text to stdout. I want to see all this output in my terminal, and at the same time I want to filter some lines and save them in a file. Example: $ myscript Line A Line B ...
47
votes
13answers
84k views

How to print all lines after a match up to the end of the file?

Input file1 is: dog 123 4335 cat 13123 23424 deer 2131 213132 bear 2313 21313 I give the match the pattern from in other file ( like dog 123 4335 from file2). I match the pattern of the line is ...
40
votes
5answers
67k views

How can I find all files that do NOT contain a text string?

What concise command can I use to find all files that do NOT contain a text string? I tried this (using -v to invert grep's parameters) with no luck: find . -exec grep -v -l shared.php {} \; ...
5
votes
3answers
3k views

Output to be saved in file named same as the input file [duplicate]

I have one input file and run some command but want the output to be saved with the same name as the input file has. I tried below command but it makes the output file blank: cat file1 | grep "YISHA"...
5
votes
1answer
19k views

Appending word at the end of line with sed [duplicate]

I have a code block as follows in a file: BalancerMember http://snode1:80 min=1 max=1000 loadfactor=1 timeout=30 keepalive=on route=tc_snode1 BalancerMember http://snode2:80 min=1 max=1000 ...
108
votes
4answers
385k views

Return only the portion of a line after a matching pattern

So pulling open a file with cat and then using grep to get matching lines only gets me so far when I am working with the particular log set that I am dealing with. It need a way to match lines to a ...
67
votes
7answers
56k views

Show all the file up to the match

grep --before-context 5 shows 5 lines before the match. I want to show everything before the match. Doing grep --before-context 99999999 would work but it is not very... professional. How to show ...
24
votes
9answers
75k views

How can I “grep” patterns across multiple lines?

It seems I am misusing grep/egrep. I was trying to search for strings in multiple line and could not find a match while I know that what I'm looking for should match. Originally I thought that my ...
13
votes
5answers
5k views

How to search files where two different words exist?

I'm looking for a way to search files where two word instances exist in the same file. I've been using the following to perform my searches up to this point: find . -exec grep -l "FIND ME" {} \; ...
41
votes
4answers
33k views

grep: memory exhausted

I was doing a very simple search: grep -R Milledgeville ~/Documents And after some time this error appeared: grep: memory exhausted How can I avoid this? I have 10GB of RAM on my system and few ...
4
votes
2answers
4k views

Use of quotes in GNU grep regular expressions

I could see that certain patterns in the GNU Grep can be enclosed within brackets and certain others need not be. For example, matching the beginning of a word works only if it is enclosed within ...
614
votes
13answers
1.4m views

How do I grep for multiple patterns with pattern having a pipe character?

I want to find all lines in several files that match one of two patterns. I tried to find the patterns I'm looking for by typing grep (foo|bar) *.txt but the shell interprets the | as a pipe and ...
272
votes
5answers
300k views

What is the difference between `grep`, `egrep`, and `fgrep`?

Can anyone tell me the technical differences between grep, egrep, and fgrep and provide suitable examples? When do I need to use grep over egrep and vice versa?
16
votes
4answers
72k views

Finding the ID of a process and killing it

When ever I need to kill a background process I do ps -e | grep <process_name> Which prints something like this 1766 ? 00:00:13 conky , Then I use the process ID to kill it like so kill 1766 . ...
13
votes
3answers
3k views

How can I redirect matching lines to a file, and non-matching lines to a different file?

Is there a script/program/utility already available for the following requirement in a optimised way? someCommand | tee >(grep "pattern" > LinesWhichMatch) | grep -v "pattern" > ...
10
votes
2answers
1k views

grep strange behaviour with single letter words

I am removing stop words from a text, roughly using this code I have the following $ cat file file types extensions $ cat stopwords i file types grep -vwFf stopwords file I am expecting the ...
2
votes
5answers
1k views

List (or move) only files with a certain number of lines?

Dealing with a whole bunch of two-line config files, I'd like a way to exclude any files that have a different number of lines. So, something like: mv * destdir only if file contains exactly two ...
6
votes
1answer
5k views

find words with all vowels in order from a file

I have a large dictionary file with 300,000+ words in it and I'm trying to find all words with the vowels aeiou in that order and have only exactly 5 vowels. My current attempt does not seem to be ...
181
votes
9answers
127k views

What makes grep consider a file to be binary?

I have some database dumps from a Windows system on my box. They are text files. I'm using cygwin to grep through them. These appear to be plain text files; I open them with text editors such as ...
48
votes
3answers
38k views

What is a “loop device” when mounting?

I am mounting an iso file, and looking at this tutorial. They use the command: $ mount -o loop disk1.iso /mnt/disk I'm trying to understand the use of -o loop. I have two questions: When I look at ...
60
votes
4answers
367k views

Match exact string using grep

I have a text file: deiauk 1611516 afsdf 765 minkra 18415151 asdsf 4152 linkra sfsfdsfs sdfss 4555 deiauk1 sdfsfdsfs 1561 51 deiauk2 115151 5454 4 deiauk 1611516 afsdf ddfgfgd luktol1 4545 4 9 luktol ...
19
votes
12answers
54k views

How can I remove all comments from a file?

I have a file with comments: foo bar stuff #Do not show this... morestuff evenmorestuff#Or this I just want to print all the uncommented code: foo bar stuff morestuff evenmorestuff Being able to ...
19
votes
5answers
38k views

grep with logic operators

Is there a grep-like utility that will enable me to do grep searches with logic operators. I want to be able to nest and combine the logical constructs freely. For example, stuff like this should be ...
19
votes
2answers
1k views

Grep: unexpected results when searching for words in heading from man page

I'm running into weird behavior when trying to grep a man page on macOS. For example, the Bash man page clearly has an occurrence of the string NAME: $ man bash | head -5 | tail -1 NAME And if I ...
14
votes
5answers
14k views

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 ...
27
votes
12answers
44k views

How can I “cat” a file and remove commented lines?

I'd like to know if there is a way that I could cat file like php.ini and remove all lines starting with ; For example, if the file contained this: ; - Show all errors, except for notices ; ;...
14
votes
1answer
41k views

Find pattern from one file listed in another

I want to find patterns that are listed in one file and find them in other file. The second file has those patterns separated by commas. for e.g. first file F1 has genes ENSG00000187546 ...
14
votes
5answers
37k views

How does one extract a command's exit status into a variable?

I started learning Bash a couple of days ago. I'm trying to obtain an exit status of grep expression into a variable like this: check=grep -ci 'text' file.sh and the output that I got is No ...
6
votes
4answers
2k views

Identifying genes from a list of genes

I have a gene list file. Some thing like this SWT21 SSA1 NRP1 EFB1 TFC3 MDM10 I have another file which also contains the names of these genes in my list along with other ...
6
votes
3answers
840 views

How to find files that contain one criterion but exclude a different criterion

I have a tree of source code and I am looking to find all files that contain a certain word and must not contain a second word. This, because I need to update older files to include some newer code. ...
0
votes
1answer
152 views

Modifying the search result of grep

Normally, we can search a keyword in a list of pdf files using the following command: for file in *pdf; do pdftotext "$file" - | grep keyword done Now, from the search result, If I want to find the ...
95
votes
7answers
57k views

Is there a basic tutorial for grep, awk and sed? [closed]

I've been a Linux user for a while, and I've a pretty decent understanding of most the common command line utilities. However, ones that come up and up again in relation to programming are grep, awk, ...
63
votes
7answers
181k views

How to read first and last line from cat output?

I have text file. Task - get first and last line from file after $ cat file | grep -E "1|2|3|4" | commandtoprint $ cat file 1 2 3 4 5 Need this without cat output (only 1 and 5). ~$ cat file | ...