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

vaquitasos

The structure goes as follows:

if condition; then
   action
   action
fi

For example, if the correct number of parameters is less than one print a usage message. The $# is the total number of parameters given. -lt mean less than.

if [ $# -lt 1 ];then
   echo "You must specify a directory name"
   echo "Usage: $0 <directoryname>"
   exit 1
fi

Running the script.

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