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

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30
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7answers
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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 ...
48
votes
4answers
10k 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 ...
13
votes
2answers
13k 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 ...
32
votes
7answers
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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 ...
6
votes
4answers
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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 . ...
7
votes
2answers
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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
233 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 ...
81
votes
5answers
60k 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?
11
votes
1answer
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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"; ...
15
votes
8answers
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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?
9
votes
3answers
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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 ...
10
votes
5answers
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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 ...
2
votes
2answers
1k 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 ...
45
votes
4answers
29k 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 ...
15
votes
11answers
13k 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 ...
13
votes
2answers
44k 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 ...
18
votes
2answers
3k 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: ...
8
votes
4answers
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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 ...
16
votes
3answers
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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 ...
5
votes
4answers
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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 ...
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 ...
4
votes
4answers
364 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 ...
58
votes
4answers
136k 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 ...
81
votes
10answers
17k 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 ...
17
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10answers
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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?
13
votes
2answers
55k 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
5answers
70k views

grep: count total number of occurrences

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 ...
4
votes
3answers
3k 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 ...
25
votes
3answers
1k views

Multicolored Grep

I'm trying to get each grep command to highlight it's results in a different color. I can do it manually with a line like this: ls -l GREP_COLORS='mt=01;32' grep c | GREP_COLORS='mt=01;31' grep o | ...
6
votes
7answers
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How do I find text within a file and have it search multiple subfolders?

I'm looking for a function name and the folder structure is deep and there are a lot of files to look though. Usually I go with something like find * | grep functionname but is that the best way?
4
votes
2answers
3k 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 ...
7
votes
2answers
696 views

Why is `tac file | grep foo' (piping) faster than `grep foo < <(tac file)' (process substitution)?

This question was motivated by "Reverse grepping", about grepping a huge file from bottom up. @chaos said: tac file | grep whatever Or a bit more effective: grep whatever < <(tac file) ...
12
votes
2answers
3k views

grep: Find all lines that contain Japanese kanjis

In a huge UTF-8 text file, I want to show all lines that contains Japanese kanjis. What grep (or other) expression does this? If I am not mistaken, kanjis are the characters between \u4e00 and ...
10
votes
5answers
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How to display lines 2-4 after each grep result?

I'm parsing a mailbox file that stores e-mail server reports for unsuccessfully delivered e-mail. I wish to extract bad e-mail addresses, so that I remove them from the system. The log file looks like ...
6
votes
1answer
160 views

What is the meaning of this test expression []? [duplicate]

I've seen someone use command: ps -ef | grep [h]ttpd and Output is: apache 25125 31006 0 21:54 ? 00:00:00 /usr/sbin/httpd apache 26869 31006 0 22:04 ? 00:00:00 ...
5
votes
1answer
1k views

Find all lines between a line matching a pattern and a line matching another pattern

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 didnt work. Input: kkkkkkkkkkk ...
4
votes
2answers
482 views

Searching for string in files

Is there an easy way to search inside 1000s of files in a complex directory structure to find files which contain a specific string within the file?
3
votes
2answers
1k views

Concatenate specific files into one single file

In a folder containing X files, I need to concatenate Y files (where X > Y) together into a single text file. I have the filenames (of Y files) that I need to concatenate. Can anyone please help me ...
3
votes
1answer
8k views

Read log file between two dates

I have to read log file between and my question is how to get only the text in the file wich is between two dates using unix commands? Every line contain date and I want to get the text in the file ...
2
votes
3answers
725 views

Command substitution in for loop not working

I want to keep all files not ending with .bat I tried for f in $(ls | egrep -v .bat); do echo $f; done and for f in $(eval ls | egrep -v .bat); do echo $f; done But both approaches yield the ...
2
votes
2answers
374 views

Web front-end to find/grep/ack

In my lab, we are trying to build a web that allows the user to enter queries for find, ack, grep on a specific directory. The web would return an HTML with a table of a list of clickable files (click ...
1
vote
1answer
3k views

How to grep a text recursively on BusyBox 1.0?

How can I find a file containing a certain string on a BusyBox 1.0, if grep -r does not work?
7
votes
4answers
8k 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?
6
votes
2answers
4k views

grep surrounding characters of a match

I'm looking to do a find and replace within a giant database dump, and it's not doing what I think should happen. I'd like to grep for my target string in the file, and then see the surrounding 8 ...
5
votes
3answers
5k views

How to combine two grep statements and display their results together?

Suppose I do grep "MyVariable = False" FormA.frm ... result1 grep "MyVariable = True" FormA.frm ... result2 How to write the grep command so that I can say something like grep ...
4
votes
4answers
617 views

How can I grep for a string containing regex metacharacters like $ and '?

I want to search all files in the current directory and below for the substring $form['#node']. So, I have tried, initially: grep -R "\$form\[\\\\'" . and grep -R "\$form\[\'" . But it returns no ...
4
votes
2answers
1k 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 ...
4
votes
3answers
878 views

Delete the matching line and several more from a file

I have a text file called file_a.txt. My first command is grep -A 12 ".production =" file_a.txt The output is a few block. Each block of string contains 13 rows I specifically want to delete all ...
3
votes
3answers
122 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 ...
3
votes
3answers
604 views

How can I delete all text between curly brackets in a multiline text file?

Example: This is { the multiline text file } that wants { to be changed } anyway. Should become: This is that wants anyway. I have found some similar threads in the forum, but they don't seem ...