My blog

Category: Automation and scripts

  • Bash useful sites

  • Bash for loop

    Below code will print 0 to 100 in bash shell

    for ((i = 0 ; i < 100 ; i++)); do
  echo "$i"
done

    Ranges for for loop

    for i in {1..5}; do
    echo "Welcome to my blog $i"
done

Expected result
Welcome to my blog 1
Welcome to my blog 2
Welcome to my blog 3
Welcome to my blog 4
Welcome to my blog 5

    With step size of 5

    for i in {5..50..5}; do
    echo "Welcome to my blog  $i"
done

Expected result
Welcome to my blog  5
Welcome to my blog  10
Welcome to my blog  15
Welcome to my blog  20
Welcome to my blog  25
Welcome to my blog  30
Welcome to my blog  35
Welcome to my blog  40
Welcome to my blog  45
Welcome to my blog  50

    Reading lines from a file (file created with few line)

    lab01> while read -r line; do echo “$line”; done <file.txt

    Expected output from file

    apple
    orange
    toy
    car
    bus
    auto

    While loop executing every 30 sec with sleep command

    lab01> while true; do ps -ef | grep 'ssh';sleep 30;done

    Listing files in a directory

    for file in *; do echo $file; done

  • Bash shell environment variable

    There are several environment variables in bash shell among them few are listed below

    echo $PWD ———This will print the current directory

    echo $SHELL ——-This will print the shell details

    echo $PS1 —-Print the Prompt

    echo $PATH —This will print the search path

    We can set these environmental variable in the shell using below commands.

    export PS1=’lab01> ‘ –This will set the prompt as lab01>

  • My first bash script

    What is BASH shell?

    Bash is built in shell in most of the Linux operating systems. Its the shell that directly interact with the operating system and executes the commands. Let us write as basic bash shell script that will print a hello message.

    #!/bin/bash
echo " This is my first bash script"

    save the code in a file name as script01.sh and execute on the Linux shell. The out put will be as below show:

    lab01> bash script01.sh
    This is my first bash script