String operators

Highest precedence

`(`expression`)`	parentheses
string `x` number	replication (returns number concatenated copies of string)
string `.` string	concatenation
`-r` filename `-w` filename `-x` filename `-e` filename `-z` filename `-s` filename `-f` filename `-d` filename `-T` filename `-B` filename `-M` filename `-A` filename `-C` filename	file is readable file is writable file is executable file exists file has zero size file size (in bytes) file is an ordinary file file is a directory file is a text file file is a binary file number of days ago that the file was last modified number of days ago that the file was last accessed number of days ago that the file was created
string `lt` string string `gt` string string `le` string string `ge` string	less than (returns true or false) greater than (returns true or false) less than or equal (returns true or false) greater than or equal (returns true or false)
string `eq` string string `ne` string string `cmp` string	equal (returns true or false) not equal (returns true or false) comparison (returns -1, 0, +1)
variable `=` expression variable op`=` expression	assign the value of the expression to the variable, and return that value equivalent to variable `=` variable op expression, where op is one of `.`

Lowest precedence