strnlen - determine the length of a fixed-size string
size_t strnlen(const char *s, size_t maxlen);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
Since glibc 2.10: _XOPEN_SOURCE >= 700 || _POSIX_C_SOURCE >= 200809L Before glibc 2.10: _GNU_SOURCE
The strnlen() function returns the number of bytes in the string pointed to by s, excluding the terminating null bye ( \0 ), but at most maxlen. In doing this, strnlen() looks only at the first maxlen bytes 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 null byte ( \0 ) among the first maxlen bytes pointed to by s.
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