Predefined macro
This macro returns the string length. It counts the number of characters in a string up to but not including the NUL terminating character.
This macro behaves like the strlen function in the ANSI C string library.
Syntax:
unsigned long strlen (str1)
char *str1;
where:
str1 Specifies the location in memory of the first byte of a character string.
Return Value
unsigned long The number of characters in the string pointed to by str1, not including the terminating NUL character.
Rules
Strings are assumed to be NUL terminated.
If str1 is not properly terminated by a NUL character, the length returned is invalid.