> write to fixed size data structures such as part of the filesystem where you don't want to store NUL termination on strings
... AND where you want to pad the remaining space with zero bytes, so that you don't leak uninitialized memory onto the disk, or network.
The null byte padding behavior of strncpy makes it clear what the intended use was.
Also, the way C initializes character arrays from literals has strncpy-like behavior, because the entire aggregate is initialized, so the extra bytes are all zero:
char a[4] = "a"; // like strncpy(a, "a", 4);
char b[4] = "abcd"; // like strncpy(a, "abcd", 4);
the compiler could literally emit strncpy calls to do these initializations, so we might say that strncpy is a primitive that is directly relevant for run-time support for a C declaration feature.
... AND where you want to pad the remaining space with zero bytes, so that you don't leak uninitialized memory onto the disk, or network.
The null byte padding behavior of strncpy makes it clear what the intended use was.
Also, the way C initializes character arrays from literals has strncpy-like behavior, because the entire aggregate is initialized, so the extra bytes are all zero:
the compiler could literally emit strncpy calls to do these initializations, so we might say that strncpy is a primitive that is directly relevant for run-time support for a C declaration feature.