5.9 Writing Programs

5.9.5 Exercises

Below this list of exercises you can find examples of how the programs described here should work when used on the command line.

1. Make a script executable.

2. Put that script in a directory that you create and make that directory part of your PATH.

3. Write a program called range that takes one number as an argument and prints all of the numbers between that number and 0.

4. Write a program called extremes which prints the maximum and minimum values of a sequence of numbers.

$ range 6

## 0 1 2 3 4 5 6

$ range -3

## -3 -2 -1 0

$ extremes 8 2 9 4 0 3

## 0 9

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Solutions

1. Suppose we have a script named script_name.sh in the home directory:

   • Method 1: Valid for the current shell session

     Write this in the shell:

      source script_name.sh
     

   • Method 2: Valid forever

     Write this in the ~/.bash_profile or ~/.bashrc

      source script_name.sh
     

     Then, write this in the shell

      source ~/.bash_profile # or ~/.bashrc
     

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1. Making the script directory a part of PATH:

    mv script_name.sh my_dir/script_name.sh
   
    export PATH=my_dir:$PATH
   
    source ~/.bash_profile # or ~/.bashrc
   

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1. range

    function range
    {
        local arr=($(eval echo {0..$1}))
   
        echo ${arr[*]}
    }
   
    # Test:
    # range $1
    # or source your script and call in the command line
   

---

1. extremes

    function extremes
    {
        local min=$1
        local max=$1
   
        for i in $@
        do
            [[ $i -lt $min ]] && let min=$i
            [[ $i -gt $max ]] && let max=$i
        done
   
        echo $min $max
    }
   
    # Test:
    # extremes $@
    # or source your script then call in the command line