Category: Linux Commands


Add text in the beginning of the file

  1. Suppose you had a text file with the contents and you wanted to insert a string to the beginning:
    1st line
    2nd line
    3rd line
  2. Run the command:
    sed -i '1i Top of the file!' <filename>
  3. Now the file will look like this:
    Top of the file!
    1st line
    2nd line
    3rd line

A brief explanation of the sed command parameters that we used:
-i : This will update the contents of the file and automatically save it
1i : This means, insert to the 1st line of the file

Add text at the end of the file

  1. To append the string “hello” to file greetings.txt
    echo "hello" >> greetings.txt
  2. To append the contents of the file temp.txt to file data.txt
    cat temp.txt >> data.txt
  3. To append the current date/time timestamp to the file dates.txt
    date >> dates.txt
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Easily you can edit the file:

gedit ~/.config/nautilus/servers

You can edit the file and remove some entries or if you just want to delete all history you can remove this file:

rm ~/.config/nautilus/servers

Check Ubuntu Version

Check Ubuntu version from terminal:

Step 1: Open the terminal.

Step 2: Enter the lsb_release -a command.

netstat – a command-line tool that displays network connections, routing tables, and a number of network interface statistics.

$ sudo netstat -plnt

Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 0.0.0.0:3306 0.0.0.0:* LISTEN  1158/mysqld
tcp 0 0 127.0.0.1:6379 0.0.0.0:* LISTEN 5390/redis-server 1
tcp 0 0 0.0.0.0:139 0.0.0.0:* LISTEN 699/smbd
tcp 0 0 0.0.0.0:9391 0.0.0.0:* LISTEN 4938/openvassd: Wai
tcp 0 0 192.168.122.1:53 0.0.0.0:* LISTEN 2218/dnsmasq
tcp 0 0 127.0.1.1:53 0.0.0.0:* LISTEN 1345/dnsmasq
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 1029/sshd
tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN 7420/cupsd
tcp 0 0 127.0.0.1:5943 0.0.0.0:* LISTEN 1320/teamviewerd
tcp 0 0 127.0.0.1:5432 0.0.0.0:* LISTEN 1271/postgres
tcp 0 0 0.0.0.0:25 0.0.0.0:* LISTEN 2140/master
tcp 0 0 0.0.0.0:445 0.0.0.0:* LISTEN 699/smbd
tcp6 0 0 :::139 :::* LISTEN 699/smbd
tcp6 0 0 :::9390 :::* LISTEN 4962/openvasmd
tcp6 0 0 :::9392 :::* LISTEN 5442/gsad
tcp6 0 0 :::80 :::* LISTEN 2367/apache2
tcp6 0 0 :::22 :::* LISTEN 1029/sshd
tcp6 0 0 ::1:631 :::* LISTEN 7420/cupsd
tcp6 0 0 :::25 :::* LISTEN 2140/master
tcp6 0 0 :::443 :::* LISTEN 5201/gsad
tcp6 0 0 :::445 :::* LISTEN 699/smbd

Here is the Command:

grep -rnw 'directory' -e "pattern"

-r or -R is recursive
-n is line number
-w stands match the whole word
-l (letter L) can be added to have just the file name.


							

Rename File Extension

Change .jpeg to .jpg

rename ‘s#\.jpeg$#.jpg#’ *.jpeg

Chang .jpg to .JPG

rename ‘s#\.jpg$#.JPG#’ *.jpg

Basic Format

grep -rl matchstring somedir/ | xargs sed -i 's/string1/string2/g'

Example

grep -rl 'windows' ./ | xargs sed -i 's/windows/linux/g'

To find number of files in a directory use the following command:

ls | wc -l

To find number for rows in a csv file use the following command:

wc -l filename.csv

grep command syntax

The syntax is:

grep "text string to search” directory-path

OR

grep [option] "text string to search” directory-path

OR

grep -r "text string to search” directory-path

OR

grep -r -H "text string to search” directory-path

OR

egrep -R "word-1|word-2” directory-path

OR

egrep -w -R "word-1|word-2” directory-path