fgetln - get a line from a stream
Utility functions from BSD systems (libbsd, -lbsd)
fgetln(FILE *stream, size_t *len);
The fgetln() function returns a pointer to the next line from the stream
referenced by stream. This line is not a C string as it does not end
with a terminating NUL character. The length of the line, including the
final newline, is stored in the memory location to which len points and
is guaranteed to be greater than 0 upon successful completion. (Note,
however, that if the line is the last in a file that does not end in a
newline, the returned text will not contain a newline.)
Upon successful completion a pointer is returned; this pointer becomes
invalid after the next I/O operation on stream (whether successful or
not) or as soon as the stream is closed. Otherwise, NULL is returned.
The fgetln() function does not distinguish between end-of-file and error;
the routines feof(3) and ferror(3) must be used to determine which
occurred. If an error occurs, the global variable errno is set to
indicate the error. The end-of-file condition is remembered, even on a
terminal, and all subsequent attempts to read will return NULL until the
condition is cleared with clearerr(3).
The text to which the returned pointer points may be modified, provided
that no changes are made beyond the returned size. These changes are
lost as soon as the pointer becomes invalid.
[EBADF] The argument stream is not a stream open for reading.
The fgetln() function may also fail and set errno for any of the errors
specified for the routines fflush(3), malloc(3), read(2), stat(2), or
ferror(3), fgets(3), fgetwln(3), fopen(3), putc(3)
The fgetln() function first appeared in 4.4BSD.