Topic 10

Date: 3/22/2017
Linux shell scripting tutorial
Linux System Administration


if and case statements

  • Script ifsh.sh
    #!/bin/bash 
    X=10
    Y=5
    if [ "$X" -gt "$Y" ]; then
            echo "$X is greater than $Y"
    elif [ "$X" -lt "$Y"]; then
            echo "$X is less than $Y"
    else
            echo "$X is equal to $Y"
    fi
    

  • Script myprog.sh
    #!/bin/bash
    case $1 in
            --test|-t)
                    echo "you used the --test option"
                    exit 0
            ;;
            --help|-h)
                    echo "Usage:"
                    echo "        myprog.sh [--test|--help|--version]"
                    exit 0
            ;;
            --version|-v)
                    echo "myprog.sh version 0.0.1"
                    exit 0
            ;;
            -*)
                    echo "No such option $1"
                    echo "Usage:"
                    echo "        myprog.sh [--test|--help|--version]"
                    exit 1
            ;;
    esac
    echo "You typed \"$1\" on the command-line"
    

    Note, always watch for correct syntax of case statement:
    case string
    in
      regex1)
      commands1
    
       ;;
      regex2)
      commands2
       ;;
     ........
    esac
    
    Where regex is a regular expression to match the string. To catch all remaining strings, use *) at the end.


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