bash Expressions

• There are two forms of logical expressions, the “old kind” (Bourne shell compatible) and the new kind.

• Bourne shell (sh) compatible

[ $a -eq $b ]

[-e "filename" ]

• bash version 2 and up

(( $a == $b )) # numeric

[[ -e "filename" ]] # string

• The (( ... )) form can also be used in place of the let command.

• Hey, what's that -e thingie?