Hack The Sec-Leading Resource Of Linux Tutorial: Linux_grep

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<span style="color: #0b5394; font-family: verdana, geneva, sans-serif; font-size: large;"><u>Find files containing specific text in Linux</u></span></div>
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<span style="color: #0b5394; font-family: verdana, geneva, sans-serif;"><span style="font-size: 15px;"><u>Find files containing specific text using grep command</u></span></span><br />
<span style="color: #333333; font-family: verdana, geneva, sans-serif;"><span style="font-size: 15px;">grep is a command-line utility for searching plain-text data sets for lines that match a regular expression. Its name comes from the ed command g/re/p (globally search a regular expression and print), which has the same effect: doing a global search with the regular expression and printing all matching lines. Grep was originally developed for the Unix operating system, but later available for all Unix-like systems.</span></span><br />
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<span style="color: #0b5394; font-family: verdana, geneva, sans-serif;"><span style="font-size: 15px;"><u><b>grep command syntax</b></u></span></span><br />
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<pre style="background: rgb(68, 67, 65); border-radius: 6px; border: 1px solid rgb(227, 227, 227); box-sizing: border-box; clear: none !important; margin-bottom: 10px !important; margin-top: 10px !important; overflow: auto; padding: 10px !important; width: auto !important; word-break: break-all;"><span style="color: white; font-family: monospace, serif;"><span style="font-size: 14px;">grep "text string to search” directory-path</span></span></pre>
<pre style="background: rgb(68, 67, 65); border-radius: 6px; border: 1px solid rgb(227, 227, 227); box-sizing: border-box; clear: none !important; margin-bottom: 10px !important; margin-top: 10px !important; overflow: auto; padding: 10px !important; width: auto !important; word-break: break-all;"><span style="color: white; font-family: monospace, serif;"><span style="font-size: 14px;">grep [option] "text string to search” directory-path</span></span></pre>
<pre style="background: rgb(68, 67, 65); border-radius: 6px; border: 1px solid rgb(227, 227, 227); box-sizing: border-box; clear: none !important; margin-bottom: 10px !important; margin-top: 10px !important; overflow: auto; padding: 10px !important; width: auto !important; word-break: break-all;"><span style="color: white; font-family: monospace, serif;"><span style="font-size: 14px;">grep -r "text string to search” directory-path</span></span></pre>
<pre style="background: rgb(68, 67, 65); border-radius: 6px; border: 1px solid rgb(227, 227, 227); box-sizing: border-box; clear: none !important; margin-bottom: 10px !important; margin-top: 10px !important; overflow: auto; padding: 10px !important; width: auto !important; word-break: break-all;"><span style="color: white; font-family: monospace, serif;"><span style="font-size: 14px;">grep -r -H "text string to search” directory-path</span></span></pre>
<pre style="background: rgb(68, 67, 65); border-radius: 6px; border: 1px solid rgb(227, 227, 227); box-sizing: border-box; clear: none !important; margin-bottom: 10px !important; margin-top: 10px !important; overflow: auto; padding: 10px !important; width: auto !important; word-break: break-all;"><span style="color: white; font-family: monospace, serif;"><span style="font-size: 14px;">egrep -R "word-1|word-2” directory-path</span></span></pre>
<pre style="background: rgb(68, 67, 65); border-radius: 6px; border: 1px solid rgb(227, 227, 227); box-sizing: border-box; clear: none !important; margin-bottom: 10px !important; margin-top: 10px !important; overflow: auto; padding: 10px !important; width: auto !important; word-break: break-all;"><span style="color: white; font-family: monospace, serif;"><span style="font-size: 14px;">egrep -w -R "word-1|word-2” directory-path</span></span></pre>
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<span style="color: #0b5394; font-family: verdana, geneva, sans-serif;"><span style="font-size: 15px;"><u>Find files containing specific text using grep command examples</u></span></span></div>
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<span style="border: 0px none; box-sizing: border-box; color: #993300; list-style: none; margin: 0px; outline: none; padding: 0px;"><span style="color: #333333; font-family: verdana, geneva, sans-serif; font-size: 15px;"><br /></span></span></div>
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<span style="border: 0px none; box-sizing: border-box; font-size: 15px; list-style: none; margin: 0px; outline: none; padding: 0px;"><span style="color: #333333; font-family: verdana, geneva, sans-serif;">In this example, we will search for 'PULSEAUDIO_SYSTEM_START' in all configuration files located in /etc directory.</span></span></div>
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<span style="border: 0px none; box-sizing: border-box; font-size: 15px; list-style: none; margin: 0px; outline: none; padding: 0px;"><span style="color: #333333; font-family: verdana, geneva, sans-serif;"><br /></span></span></div>
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<span style="border: 0px none; box-sizing: border-box; list-style: none; margin: 0px; outline: none; padding: 0px;"><span style="color: #333333; font-family: verdana, geneva, sans-serif;"><span style="font-size: 15px;">Now there's a small problem, depending on your Linux distro, Find command Syntax can be slightly different.</span></span></span></div>
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<span style="border: 0px none; box-sizing: border-box; list-style: none; margin: 0px; outline: none; padding: 0px;"><span style="color: #333333; font-family: verdana, geneva, sans-serif;"><span style="font-size: 15px;"><br /></span></span></span></div>
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<span style="border: 0px none; box-sizing: border-box; font-size: 15px; list-style: none; margin: 0px; outline: none; padding: 0px;"><span style="color: #333333; font-family: verdana, geneva, sans-serif;">*If you know the exact location and directory you're after, then use</span></span></div>
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<span style="border: 0px none; box-sizing: border-box; list-style: none; margin: 0px; outline: none; padding: 0px;"><pre style="background: rgb(68, 67, 65); border-radius: 6px; border: 1px solid rgb(227, 227, 227); box-sizing: border-box; clear: none !important; margin-bottom: 10px !important; margin-top: 10px !important; overflow: auto; padding: 10px !important; width: auto !important; word-break: break-all;"><span style="color: white; font-family: monospace, serif;"><span style="font-size: 14px;">root@hackthesec:~# grep "PULSEAUDIO_SYSTEM_START" /etc/default/pulseaudio 
PULSEAUDIO_SYSTEM_START=1</span></span><span style="color: #333333; font-family: verdana, geneva, sans-serif;"><span style="font-size: 15px; white-space: normal;">
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<span style="color: #333333; font-family: verdana, geneva, sans-serif;"><span style="font-size: 15px;">*If you know the exact directory with the files containing that specific text, then use</span></span></div>
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<pre style="background: rgb(68, 67, 65); border-radius: 6px; border: 1px solid rgb(227, 227, 227); box-sizing: border-box; clear: none !important; margin-bottom: 10px !important; margin-top: 10px !important; overflow: auto; padding: 10px !important; width: auto !important; word-break: break-all;"><span style="color: white; font-family: monospace, serif;"><span style="font-size: 14px;">root@hackthesec:~# grep "PULSEAUDIO_SYSTEM_START" /etc/default/*
grep: /etc/default/kdm.d: Is a directory
/etc/default/pulseaudio:PULSEAUDIO_SYSTEM_START=1
root@hackthesec:~#</span></span><span style="color: #333333; font-family: verdana, geneva, sans-serif;"><span style="font-size: 15px; white-space: normal;">
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<span style="color: #333333; font-family: verdana, geneva, sans-serif;"><span style="font-size: 15px;">If you don't know the exact location of the file that contains the specific text you’re looking for, then you need to search all sub-directories recursively.</span></span></div>
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<pre style="background: rgb(68, 67, 65); border-radius: 6px; border: 1px solid rgb(227, 227, 227); box-sizing: border-box; clear: none !important; margin-bottom: 10px !important; margin-top: 10px !important; overflow: auto; padding: 10px !important; width: auto !important; word-break: break-all;"><span style="color: white; font-family: monospace, serif;"><span style="font-size: 14px;">root@hackthesec:~# grep -r "PULSEAUDIO_SYSTEM_START" /etc/default/*
/etc/default/pulseaudio:PULSEAUDIO_SYSTEM_START=1
root@hackthesec:~#</span></span></pre>
<pre style="background: rgb(68, 67, 65); border-radius: 6px; border: 1px solid rgb(227, 227, 227); box-sizing: border-box; clear: none !important; margin-bottom: 10px !important; margin-top: 10px !important; overflow: auto; padding: 10px !important; width: auto !important; word-break: break-all;"><span style="color: white; font-family: monospace, serif;"><span style="font-size: 14px;">root@hackthesec:~# grep -R "PULSEAUDIO_SYSTEM_START" /etc/default/*
/etc/default/pulseaudio:PULSEAUDIO_SYSTEM_START=1
root@hackthesec:~#</span></span></pre>
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<span style="font-family: verdana, geneva, sans-serif;"><span style="font-size: 15px;"><span style="color: #333333;">Now what if you are searching through a massive file and there might be many outputs similar to what you’re looking for.. you might want to use </span><span style="color: red;">--col</span><span style="color: #333333;"> flag to color code your output which searching files containing specific strings.</span></span></span></div>
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<pre style="background: rgb(68, 67, 65); border-radius: 6px; border: 1px solid rgb(227, 227, 227); box-sizing: border-box; clear: none !important; margin-bottom: 10px !important; margin-top: 10px !important; overflow: auto; padding: 10px !important; width: auto !important; word-break: break-all;"><span style="color: white; font-family: monospace, serif;"><span style="font-size: 14px;">root@hackthesec:~# grep --col 'usb 1-1.4' /var/log/messages
Apr 4 09:14:25 kali kernel: [1191164.780496] usb 1-1.4: new low-speed USB device number 21 using ehci-pci
root@hackthesec:~#</span></span></pre>
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<span style="color: #333333; font-family: verdana, geneva, sans-serif;"><span style="font-size: 15px;">Now I want to display all files with colorer output with containing specific text and instead of showing the whole content of the files</span></span></div>
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<pre style="background: rgb(68, 67, 65); border-radius: 6px; border: 1px solid rgb(227, 227, 227); box-sizing: border-box; clear: none !important; margin-bottom: 10px !important; margin-top: 10px !important; overflow: auto; padding: 10px !important; width: auto !important; word-break: break-all;"><span style="color: white; font-family: monospace, serif;"><span style="font-size: 14px;">root@hackthesec:~# grep --col -r 'Linux version 3.14-kali1' /var/log/* | cut -d: -f1
/var/log/dmesg
/var/log/dmesg.0
/var/log/installer/syslog
root@hackthesec:~#</span></span></pre>
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<span style="color: #333333; font-family: verdana, geneva, sans-serif;"><span style="font-size: 15px;">When you're using grep, depending on the commands used and permission you have on the system, you might see any of the following errors.</span></span></div>
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<span style="color: #333333; font-family: verdana, geneva, sans-serif;"><span style="font-size: 15px;"><br /></span></span></div>
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<span style="color: #351c75; font-family: verdana, geneva, sans-serif;"><span style="font-size: 15px;">* Input/output error</span></span></div>
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<span style="color: #351c75; font-family: verdana, geneva, sans-serif;"><span style="font-size: 15px;">* recursive directory loop</span></span></div>
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<span style="color: #351c75; font-family: verdana, geneva, sans-serif;"><span style="font-size: 15px;">* No such file or directory</span></span></div>
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<span style="color: #351c75; font-family: verdana, geneva, sans-serif;"><span style="font-size: 15px;">* No such device or address</span></span></div>
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<span style="color: #351c75; font-family: verdana, geneva, sans-serif;"><span style="font-size: 15px;">* Permission denied</span></span></div>
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<span style="color: #333333; font-family: verdana, geneva, sans-serif;"><span style="font-size: 15px;"><br /></span></span></div>
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<span style="font-family: verdana, geneva, sans-serif;"><span style="font-size: 15px;"><span style="color: #333333;">If you want to hide all errors or warning message spamming your output window(specifically useful when you're trying to use grep on a script) generated by the grep command, </span><span style="color: red;">append 2>/dev/null</span><span style="color: #333333;"> to grep command. This will send and hide unwanted output to </span><span style="color: red;">/dev/null</span><span style="color: #333333;"> device:</span></span></span></div>
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<pre style="background: rgb(68, 67, 65); border-radius: 6px; border: 1px solid rgb(227, 227, 227); box-sizing: border-box; clear: none !important; margin-bottom: 10px !important; margin-top: 10px !important; overflow: auto; padding: 10px !important; width: auto !important; word-break: break-all;"><span style="color: white; font-family: monospace, serif;"><span style="font-size: 14px;">root@hackthesec:~# grep -R "PULSEAUDIO_SYSTEM_START" /etc/* 2>/dev/null 
/etc/default/pulseaudio:PULSEAUDIO_SYSTEM_START=1
/etc/init.d/pulseaudio:PULSEAUDIO_SYSTEM_START=0
/etc/init.d/pulseaudio:if [ "$PULSEAUDIO_SYSTEM_START" != "1" ]; then
/etc/rc0.d/K01pulseaudio:PULSEAUDIO_SYSTEM_START=0
/etc/rc0.d/K01pulseaudio:if [ "$PULSEAUDIO_SYSTEM_START" != "1" ]; then
/etc/rc1.d/K01pulseaudio:PULSEAUDIO_SYSTEM_START=0
/etc/rc1.d/K01pulseaudio:if [ "$PULSEAUDIO_SYSTEM_START" != "1" ]; then
/etc/rc2.d/S20pulseaudio:PULSEAUDIO_SYSTEM_START=0
/etc/rc2.d/S20pulseaudio:if [ "$PULSEAUDIO_SYSTEM_START" != "1" ]; then
/etc/rc3.d/S20pulseaudio:PULSEAUDIO_SYSTEM_START=0
/etc/rc3.d/S20pulseaudio:if [ "$PULSEAUDIO_SYSTEM_START" != "1" ]; then
/etc/rc4.d/S20pulseaudio:PULSEAUDIO_SYSTEM_START=0
/etc/rc4.d/S20pulseaudio:if [ "$PULSEAUDIO_SYSTEM_START" != "1" ]; then
/etc/rc5.d/S20pulseaudio:PULSEAUDIO_SYSTEM_START=0
/etc/rc5.d/S20pulseaudio:if [ "$PULSEAUDIO_SYSTEM_START" != "1" ]; then
/etc/rc6.d/K01pulseaudio:PULSEAUDIO_SYSTEM_START=0
/etc/rc6.d/K01pulseaudio:if [ "$PULSEAUDIO_SYSTEM_START" != "1" ]; then
root@hackthesec:~#</span></span></pre>
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<span style="color: #333333; font-family: verdana, geneva, sans-serif;"><span style="font-size: 15px;"><div>
What if you're not sure about the case of the text you're after? You can use -i to ignore case.</div>
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Below example shows the difference between -i flag. First command didn’t find the text, second command did as we used -i flag to ignore case.</div>
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<pre style="background: rgb(68, 67, 65); border-radius: 6px; border: 1px solid rgb(227, 227, 227); box-sizing: border-box; clear: none !important; margin-bottom: 10px !important; margin-top: 10px !important; overflow: auto; padding: 10px !important; width: auto !important; word-break: break-all;"><span style="color: white; font-family: monospace, serif;"><span style="font-size: 14px;">root@hackthesec:~# grep -r "pulseaudio_system_start" /etc/default/*
root@hackthesec:~# 
root@hackthesec:~# grep -i  -r "pulseaudio_system_start" /etc/default/*
/etc/default/pulseaudio:PULSEAUDIO_SYSTEM_START=1
root@hackthesec:~#</span></span></pre>
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<span style="font-family: verdana, geneva, sans-serif;"><span style="font-size: 15px;"><span style="color: #333333;">I always prefer using grep command </span><span style="color: red;">with -r and --col flag in Debian Linux as -r complains less about permissions</span><span style="color: #333333;">, files, directory etc. and of course some color helps on the eyes when you’re browsing through many lines.</span></span></span></div>
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How to find files containing specific text in Linux

Find files containing specific text in Linux Find files containing specific text using grep command grep is a command-line utility for searching plain-text data sets for lines that match a regular ex…