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

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62
votes
4answers
16k 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 ...
35
votes
9answers
9k 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 ...
21
votes
2answers
80k 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"; ...
10
votes
6answers
9k 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 ...
24
votes
3answers
33k 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 ...
23
votes
4answers
67k 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 ...
6
votes
4answers
21k 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 . ...
4
votes
3answers
800 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 ...
42
votes
7answers
33k 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 ...
2
votes
2answers
2k 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 ...
0
votes
1answer
102 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 ...
28
votes
3answers
11k 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 ...
9
votes
4answers
10k 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 ...
7
votes
2answers
2k 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
3
votes
4answers
433 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 ...
142
votes
5answers
139k views

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

Can any one tell me the technical difference between grep and egrep, and fgrep and provide a suitable example? When do I need to use grep over egrep and vice versa?
121
votes
12answers
46k 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 ...
89
votes
5answers
71k 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 ...
43
votes
11answers
36k 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?
32
votes
3answers
101k views

Can grep return true/false or are there alternative methods

I'm trying to write this script for an assignment - it's only the second one I've written so bear with me. As a part of this script, I need to be able to check if the first argument given matches ...
16
votes
11answers
18k views

Grep huge number of patterns from huge file

I have a file that's growing about 200,000 lines a day, and it is all formed with blocks of three lines as such: 1358726575123 # key Joseph Brunner # name carpenter # job ...
21
votes
3answers
21k views

Piping from grep to awk not working

I am trying to grep the ongoing tail of file log and get the nth word from a line. Example file: $ cat > test.txt <<EOL Beam goes blah John goes hey Beam goes what? John goes forget it Beam ...
7
votes
2answers
5k 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 ...
18
votes
7answers
11k views

pgrep and pkill alternatives on mac os x?

Are there alternatives to pgrep and pkill commands on Mac OS X or should I just create aliases for them using other commands available for me?
6
votes
1answer
4k views

How to grep all lines where starting line ends with a pattern and ending line ends with another?

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 ...
9
votes
4answers
13k views

Number of files containing a given string

How can I count the number of files (in a directory) containing a given string as input in bash/sh?
5
votes
3answers
2k 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" {} \; ...
3
votes
3answers
2k views

comparing the first column of two files and printing the entire row of the second file if the first columns match

I have two files in these formats: file1 : air smell hand dude road cat file 2: air,4,21,01,13,3,2 smell,21,4,2,5,6 dude,1,31,42,1 road,1,4,2,1,4 cat,1,5,6,3,1 hand,1,4,2,1,6 mouse,1,3,5,6,2 ...
16
votes
5answers
32k views

Multiline pattern match using sed, awk or grep

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. ...
25
votes
2answers
9k views

What is a “loop device” when mounting?

I am doing a mounting of 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. So I have two questions: ...
9
votes
4answers
12k views

Finding a substring in files across subdirectories with a single built-in command?

In Windows, if I wanted to find a string across all files in all subdirectories, I would do something like findstr /C:"the string" /S *.h However, in Linux (say, Ubuntu) I have found no other way ...
8
votes
6answers
12k 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 ...
13
votes
5answers
26k 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 {} \; ...
7
votes
5answers
4k 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 ...
4
votes
3answers
787 views

extract from line to line and then save to separate file

I tried my luck with grep and sed but somehow I don't manage to get it right. I have a log file which is about 8 GB in size. I need to analyze a 15 minute time period of suspicious activity. I ...
4
votes
3answers
2k views

Show lines matching a pattern and the 4 lines before each

For example, from this file: CREATE SYNONYM I801XS07 FOR I8010.I801XT07 * ERROR at line 1: ORA-00955: name is already used by an existing object CREATE SYNONYM I801XS07 FOR ...
15
votes
3answers
47k views

How do I count the number of occurrences of a word in a text file with the command line?

I have a large JSON file that is on one line, and I want to use the command line to be able to count the number of occurrences of a word in the file. How can I do that?
4
votes
4answers
522 views

Grep of many keywords over many files: speeding it up

I am currently facing a "performance problem" while using grep. I am trying to locate the occurrences of many (10,000+) keywords in many (think Linux kernel repository size) files. The objective is to ...
4
votes
2answers
3k views

Tail -f piped through grep not outputing to file, but outputs to console

I'm using the following command tail -f /mydir/myfile | grep "searchterm" >> outfile Without the -f it works fine, but with the -f, which I need, nothing is written to the file. The ...
2
votes
3answers
101 views

Searching a keyword in multiple pdf files

I want to search for a specific keyword in multiple pdf file using pdftotext command. Normally we can search inside a single pdf file using the following command: pdftotext file.pdf - | grep keyword ...
70
votes
7answers
31k 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, ...
151
votes
5answers
338k views

How do I grep for multiple patterns?

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 ...
57
votes
5answers
161k views

Count total number of occurrences using grep

grep -c is useful for finding how many times a string occurs in a file, but it only counts each occurence once per line. How to count multiple occurences per line? I'm looking for something more ...
31
votes
2answers
106k 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 ...
25
votes
6answers
4k views

Pipe to multiple files in the shell

I have an application which will produce a large amount of data which I do not wish to store onto the disk. The application mostly outputs data which I do not wish to use, but a set of useful ...
16
votes
6answers
37k views

How to grep lines which does not begin with “#” or “;”?

I want to grep smb.conf and see only lines which are not commented.
37
votes
4answers
6k views

Reverse grepping

Let's say, I have a really big text file (about 10.000.000 lines). I need to grep it from the end and save result to a file. What's the most efficient way to accomplish task?
31
votes
4answers
51k views

How to search text throughout entire file system?

Assuming that the grep tool should be used, I'd like to search for the text string "800x600" throughout the entire file system. I tried: grep -r 800x600 / but it doesn't work. What I believe my ...
6
votes
3answers
6k views

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 ...
19
votes
11answers
31k 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 ...