STRNLEN
NAME SYNOPSIS DESCRIPTION RETURN VALUE CONFORMING TO SEE ALSO
strnlen - determine the length of a fixed-size string
#include s, size_t maxlen);
The strnlen function returns the number of characters in the string pointed to by s, not including the terminating '0' character, but at most maxlen. In doing this, strnlen looks only at the first maxlen characters at s and never beyond s+maxlen.
The strnlen function returns strlen(s), if that is less than maxlen, or maxlen if there is no '0' character among the first maxlen characters pointed to by s.
This function is a GNU extension.
2 pages link to strnlen(3):