How do i use the if/elif/else conditional statements in bash shell scripts?

vaquitasos

Also see: How do i use the if/else conditional statements in bash shell scripts?

Here is the structure for if/elif/else conditionals.

if condition; then 
  action
elif condition; then 
  action
else 
  action
fi

Using the same script in How do i use the if/else conditional statements in bash shell scripts? we will expand on it.

Let's add a condition to check if the directory exists. The ! not in the elif can be within the square bracket or outside.

if [ $# -lt 1 ]; then
   echo "You must specify a directory name"
   echo "Usage: $0 <directoryname>"
   exit 1
elif ! [ -d $1 ]; then
   echo "That directory does not exist"
else 
   du -sh $1
fi

Test all conditions.

Run script as normal

$ ./dirsize.sh /home/trainer/bin
26M	/home/trainer/bin

Run script with directory that does not exist.

$ ./dirsize.sh /home/trainer/bino
That directory does not exist

Run script without a positional parameter.

$ ./dirsize.sh
You must specify a directory name
Usage: ./dirsize.sh <directoryname>