bcdef
$ set -- 01234567890abcdefgh
$ echo ${1:7}
7890abcdefgh
$ echo ${1:7:0}
$ echo ${1:7:2}
78
$ echo ${1:7:-2}
7890abcdef
$ echo ${1: -7} bcdefgh
$ echo ${1: -7:0}
$ echo ${1: -7:2} bc
$ echo ${1: -7:-2} bcdef
$ array[0]=01234567890abcdefgh
$ echo ${array[0]:7}
7890abcdefgh
$ echo ${array[0]:7:0}
$ echo ${array[0]:7:2}
78
$ echo ${array[0]:7:-2}
7890abcdef
$ echo ${array[0]: -7} bcdefgh
$ echo ${array[0]: -7:0}
$ echo ${array[0]: -7:2} bc
$ echo ${array[0]: -7:-2} bcdef
If parameter is ‘@’, the result is length positional parameters beginning at offset.
A negative offset is taken relative to one greater than the greatest positional parameter, so an offset of -1 evaluates to the last positional parameter. It is an expansion error if length evaluates to a number less than zero.
The following examples illustrate substring expansion using positional param- eters:
$ set -- 1 2 3 4 5 6 7 8 9 0 a b c d e f g h
$ echo ${@:7}
7 8 9 0 a b c d e f g h
$ echo ${@:7:0}