Bash if statements

Test

You can check if the condition is true with the command test, here are tables of possible tests.

Operator	Description
! EXP	EXP is false

Operator	Description
NUM1 -eq NUM2	NUM1 is equal to NUM2
NUM1 -ne NUM2	NUM1 is equal to NUM2
NUM1 -gt NUM2	NUM1 is greater than NUM2
NUM1 -ge NUM2	NUM1 is greater than or equal to NUM2
NUM1 -lt NUM2	NUM1 is less than NUM2
NUM1 -le NUM2	NUM1 is less than or equal to NUM2

Operator	Description
-e FILE	FILE Exists
-s FILE	FILE Exists, and is not empty
-f FILE	FILE Exists, and it’s a regular file
-d FILE	FILE Exists, and is a directory
-r FILE	FILE Exists, and it can be Read (r–)
-w FILE	FILE Exists, and it can be Written (-w-)
-x FILE	FILE Exists, and it can be eXecuted (–x)

if [ 2 -eq 2 ]
then
   echo "yes"
fi

if [ "2" = 2 ]
then
   echo "yes"
else
   echo "no"
fi

if [ 2 -ge 2 ]
then
   echo "yes"
elif [ 2 -lt 2 ]
then
   echo "no"
fi

if [ 2 -eq 2 ] && [ 2 -ge 2 ]
then
   echo "yes"
fi

if [ "2" = 2 ] || [ 2 -lt 2 ]
then
   echo "yes"
fi

case $1 in
   2)
   echo "2"
   ;;
   a)
   echo "a"
   ;;
   *)
   echo "error"
   ;;
esac