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Top 10 GREP Commands in linux to search files directory words strings

Grep command in linux explained

Grep command used for search files and search pattern. (Find Text in Files).
grep command stands for “global regular expression print
grep [options] pattern [files]

Options Description

-c : counts the frequency only
-h : Display the matched lines, but do not display the filenames.
-i : case insensitive Ignores, case for matching
-l : filenames only.(imp)
-n :  line number if word in a file
-v : lines that are not matched with the keyword
-e exp : Specifies expression with this option. Can use multiple times.
-f file : takes the file patterns
-E : Treats pattern as an extended regular expression (ERE)
-w : prints whole words in a file
-o : Print only matched words per line

Expressions

Start ^
End $
grep “^linux” mynewfile.txt
grep “ux$” mynewfile.txt
$grep –e “admin” –e “admin” –e “admin” newfile.txt
$grep –f newfile.txt  mynewfile.txt

Finding a text in list of files in a directory.

grep ‘word’ file1 file2 file3

grep -n ‘root’ /etc/passwd
grep –color root /etc/passwd

cd /etc/nginx/sites-enabled
grep job.sarkari *

root@murali:/etc/nginx/sites-enabled# grep job.sarkari *
stories:server_name job.sarkariresultz.in;

searches only current directory

grep -rnw ‘/path/to/somewhere/’ -e ‘pattern’
-r or -R is recursive,
-n is line number, and
-w stands for match the whole word.
-l (lower-case L) can be added to just give the file name of matching files.
-e is the pattern used during the search
Along with these, –exclude, –include, –exclude-dir flags could be used for efficient searching:

Grep From Files and Display the File Name On Linux

grep -l “string” filenamegrep -l root /etc/*

Searching a String / word in files & directories

root@instance-1:/etc/nginx# grep -nr ‘cache-control’ .
./conf.d/global.config:62:add_header cache-control “max-age=31536000”;
./conf.d/expires.global:5:add_header cache-control: max-age=31536000;

 

grep command to search string word in file

 

root@-s-4vcpu-8gb-blr1-01:~# grep root /etc/passwd
root:x:0:0:root:/root:/bin/bash

grep WP_CACHE_KEY_SALT /var/www/html/yoursite.com/wp-config.php

all files containing string

grep -R containing text /home/user/

grep ‘string1 string2’ filename

 

finding a file containing a particular text string

grep “find me in home” /home/tom/*.txt

grep “find me anywhere in text files “~/*.txt

root@murali:~# grep “shivajobs.in” /etc/nginx/sites-enabled/*
/etc/nginx/sites-enabled/shivafile:server_name file.shivajobs.in;
/etc/nginx/sites-enabled/shivajobs.in:root /var/www/html/shivajobs.in/;
/etc/nginx/sites-enabled/shivajobs.in:server_name shivajobs.in www.shivajobs.in;
/etc/nginx/sites-enabled/shivajobs.in:include /var/www/html/shivajobs.in/nginx.conf;
/etc/nginx/sites-enabled/shivajobs.in: if ($host = shivajobs.in) {
/etc/nginx/sites-enabled/shivajobs.in:server_name shivajobs.in shivajobs.in;
root@murali:~#

 use grep recursively

grep -R “192.168.0.1” /etc/
grep -R ‘string’ dir/
grep -R ‘expires’ /etc/nginx/
root@instance-1:/etc/nginx# grep -R ‘expires’ /etc/nginx/
/etc/nginx/rocket-nginx/default.conf: expires 30d;
/etc/nginx/rocket-nginx/default.conf: expires 30d;
/etc/nginx/rocket-nginx/default.conf: expires 30d;
/etc/nginx/rocket-nginx/rocket-nginx.tmpl: expires 30d;
/etc/nginx/rocket-nginx/rocket-nginx.tmpl: expires 30d;
/etc/nginx/rocket-nginx/rocket-nginx.tmpl: expires 30d;
/etc/nginx/sites-enabled/rajuginne: # Directives to send expires headers and turn off 404 error logging.
/etc/nginx/sites-enabled/rajuginne: expires 24h;
/etc/nginx/conf.d/default.conf: expires 31536000s;
/etc/nginx/conf.d/default.conf: expires 3600s;
/etc/nginx/conf.d/default.conf: expires 31536000s;
/etc/nginx/conf.d/headers.conf:#add_header expires $expires;
/etc/nginx/conf.d/headers.conf:map $sent_http_content_type $expires {
/etc/nginx/conf.d/browsercaching.confg: expires 3600s;
/etc/nginx/conf.d/expires.global: expires 365d;
/etc/nginx/conf.d/global2.config: expires max;
grep -R ‘add_header’ /etc/nginx/
grep -nr ‘ssl’ .
t@instance-1:/etc/nginx# grep -nr ‘ssl’ .
./nginx.conf:38: #ssl_protocols TLSv1 TLSv1.1 TLSv1.2; # Dropping SSLv3, ref: POODLE
./nginx.conf:39: #ssl_prefer_server_ciphers on;
./rocket-nginx/README.md:153:**<a name=’faq_ssl’>Will Rocket-Nginx work if my we bsite uses a SSL certificate (https) ?</a>**
./sites-enabled/f.in.conf:5:#ssl on;
./sites-enabled/ff.in.conf:6:ssl_certificate /etc/nginx/ssl/ssc.pem;
./sites-enabled/ff.in.conf:7:ssl_certificate_key /etc/nginx/ssl/ssc.key;
./sites-enabled/ffff.in:5:#listen 443 ssl http2;
./sites-enabled/.in:8:#include /etc/letsencrypt/options-ssl-nginx. conf;
The dot at the end searches the current directory. Meaning for each parameter:
-n Show relative line number in the file
‘yourString*’ String for search, followed by a wildcard character
-r Recursively search subdirectories listed
. Directory for search (current directory)
cd /etc/nginx/sites-enabled#
grep -nr ‘ssl’ .
./eaadharcard.co.in.conf:8: ssl on;
./eaadharcard.co.in.conf:9: ssl_certificate /etc/nginx/ssl/eaadharcard.co.in.pem;
./eaadharcard.co.in.conf:10: ssl_certificate_key /etc/nginx/ssl/eaadharcard.co.in.key;
./employmentnewsdaily.in:5: ssl on;

root@instance-1:~# grep . /proc/sys/net/ipv4/tcp*mem

/proc/sys/net/ipv4/tcp_mem:45525        60702   91050
/proc/sys/net/ipv4/tcp_rmem:4096        131072  6291456
/proc/sys/net/ipv4/tcp_wmem:4096        16384   4194304
root@instance-1:~#/etc/nginx/sites-enabled# grep -nr ‘rajuginni.com‘ .

linux find a file in a directory

The find command can only filter the directory hierarchy based on a file’s name and metadata. If you need to search based on the file’s content, use a tool like grep. Consider the following example:

find . -type f -exec grep “example” ‘{}’ \; -print

find command to find a file in a directory

find /path option filename

i want to ind newrelic.ini file  this directory
find /etc/php/7.4/fpm/conf.d/ newrelic
ls -l  /etc/php/7.4/fpm/conf.d/
2nd way
cd /etc/php/7.4/fpm/conf.d/
grep newrelic
/etc/php/7.4/fpm/conf.d

finding log errors with tail and grep command

tail -f /var/log/file.log | grep search_term
tail -f /var/log/nginx/error.log | grep 503
tail -f  /www/test/error_log
tail -f www/test/error_log | grep 503
tail -f www/test/error_log | grep error
tail -f www/test/error_log | grep conn

As the output of grep is buffered, Add –line-buffered to grep, and that may reduce the delay for you. Very useful in some case

tail -f /path/to/log | grep --line-buffered 'X' | grep -v 'Y'

If your grep does not have the option, you can use stdbuf as an alternative:

tail -f /path/to/log | stdbuf -oL grep 'X' | grep -v 'Y'