Delete positional parameters in Bash?

Question

You can skip positional parameters with shift but can you delete positional parameters by passing the position?

x(){ CODE; echo "$@"; }; x 1 2 3 4 5 6 7 8
> 1 2 4 5 6 7 8

I would like to add CODE to x() to delete positional parameter 3. I don't want to do echo "${@:1:2} ${@:4:8}". After running CODE, $@ should only contain "1 2 4 5 6 7 8".

Answer 1

The best way, if you want to be able to pass on the parameters to another process, or handle space separated parameters, is to re-set the parameters:

$ x(){ echo "Parameter count before: $#"; set -- "${@:1:2}" "${@:4:8}"; echo "$@"; echo "Parameter count after: $#"; }
$ x 1 2 3 4 5 6 7 8
Parameter count before: 8
1 2 4 5 6 7 8
Parameter count after: 7

To test that it works with non-trivial parameters:

$ x $'a\n1' $'b\b2' 'c 3' 'd 4' 'e 5' 'f 6' 'g 7' $'h\t8'
Parameter count before: 8
a
1 2 d 4 e 5 f 6 g 7 h   8
Parameter count after: 7

(Yes, $'\b' is a backspace)

Answer 2

x(){
    #CODE
    params=( $* )
    unset params[2]
    set -- "${params[@]}"

    echo "$@"
}

Input: x 1 2 3 4 5 6 7 8

Output: 1 2 4 5 6 7 8

Answer 3

From tldp

# The "unset" command deletes elements of an array, or entire array.
unset colors[1]              # Remove 2nd element of array.
                             # Same effect as   colors[1]=
echo  ${colors[@]}           # List array again, missing 2nd element.

unset colors                 # Delete entire array.
                             #  unset colors[*] and
                             #+ unset colors[@] also work.
echo; echo -n "Colors gone."               
echo ${colors[@]}            # List array again, now empty.