shellcommentsposixportability

Comments in between POSIX shell script's function name and its body, problem?

I wonder if I may use comments in between POSIX shell script's function name and its body? This appears not to throw any problem in shellcheck and runs in Dash / Bash, but searching for this information found me nothing useful.

Example shell functions:

is_int()
# POSIX [bool] function to test one variable for an integer.
{
    case "${1#[+-]}" in
        (*[!0123456789]*) return 1 ;;
        ('')              return 1 ;;
        (*)               return 0 ;;
    esac
}

is_uint()
# POSIX [bool] function to test one variable for an unsigned integer.
{
    case "$1" in
        ([+-]*) return 1 ;;
    esac
    is_int "$1"
}

Would any shell have known problem with this? I would not like if it hurt the portability of some of my scripts.

Attention, I only use this very recently and because VS Codium I started using supports function blocks collapsing like that:

VS Codium function blocks collapsing

Thank you.

PS: I like the comments describing functions in my shell scripts this way a bit more than having the comment above f()'s name. It is only cosmetic problem and as such please refrain from discussing the Why not above function's name. Thank you!

Solution

  • I think it is valid. The POSIX shell grammar defines a function like

    function_definition : fname '(' ')' linebreak function_body
                 ;
linebreak        : newline_list
                 | /* empty */
                 ;
newline_list     :              NEWLINE
                 | newline_list NEWLINE
                 ;

    So you can have any number of linebreaks, including zero, between () and your function body.

    And, for token recognition:

    1. If the current character is a #, it and all subsequent characters up to, but excluding, the next <newline> shall be discarded as a comment. The <newline> that ends the line is not considered part of the comment.

    I interpret this as follows: this

    is_int()
# POSIX [bool] function to test one variable for an integer.
{

    is equivalent to

    is_int()
{

    and thus valid.