I am trying to understand how busybox's awk works so I'm looking into the standard and hit weird thing which I do not fully understand why is legal. Standard ( https://pubs.opengroup.org/onlinepubs/9699919799/utilities/awk.html , in section User-Defined Functions ) states that
When invoking a function, no white space can be placed between the function name and the opening parenthesis.
The grammar shown later on is prefixed with:
This formal syntax shall take precedence over the preceding text syntax description.
non_unary_expr : '(' expr ')' | '!' expr ... | FUNC_NAME '(' expr_list_opt ')' /* no white space allowed before '(' */ | BUILTIN_FUNC_NAME '(' expr_list_opt ')' | BUILTIN_FUNC_NAME The grammar is completely same for both BUILTIN_FUNC_NAME and FUNC_NAME. Yet despite that, it behaves differently for user and builtin functions:
+$echo | awk -P '{ print length() 1 }' 01 +$echo | awk -P '{ print length () 1 }' 01 +$echo | awk -P 'function foo() { return 0 } ; { print foo() 1 }' 01 +$echo | awk -P 'function foo() { return 0 } ; { print foo () 1 }' awk: cmd. line:1: error: function `foo' called with space between name and `(', or used as a variable or an array awk: cmd. line:1: function foo() { return 0 } ; { print foo () 1 } awk: cmd. line:1: ^ syntax error awk: cmd. line:1: function foo() { return 0 } ; { print foo () 1 } awk: cmd. line:1: ^ syntax error Which part of the grammar does specify this behaviour?
