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Search text files with grep

How to use the grep tool

The grep tool is built into the operating system, so you don’t need to install it.

The simplest syntax to find a string in a single file using the grep command is:
grep ‘searched-word’ filename

By default, the search with grep is case sensitive.

Let’s gradually add the most useful options to our search.

1. Make the search case-insensitive with the "-i" option:
grep -i 'searched-word' filename
2. Search recursively in all files in a given directory with the "-r" option:
grep -ir 'searched-word' '/directory'
3. Search whole words only with the "-w" option:
grep -irw 'searched-word' '/directory'
4. Print the line numbers in which the searched word was found with the "-n" option:
grep -irwn 'searched-word' '/directory'
5. Search for multiple words syntax:
grep -ir 'word1|word2|word3' '/directory'

Many other useful grep options can be found in the official Grep Manual.

Udgivet i

Persist dns nameserver for ubuntu 14.04

If you are using ubuntu 14.04, you may find you can not setting dns on your /etc/resolv.conf

This is because ubuntu using resolvconf to manage the dns setting, every times system boot, resolvconf will regenerate resolv.conf file.

But there always have way to do this.

vim /etc/resolvconf/resolv.conf.d/head  

put your nameserver list in


then run

resolvconf -u

this command tell resolvconf to regenerate the resolve file

enjoy it.