The gets() function shall read bytes from the standard input stream,
stdin, into the array pointed to by s, until a <newline>
is read or an end-of-file condition is encountered. Any <newline> shall
be discarded and a null byte shall be placed immediately after the last byte
read into the array.
The gets() function may mark the st_atime field of the file
associated with stream for update. The st_atime field shall be
marked for update by the first successful execution of fgetc(),
fgets(), fread(), getc(), getchar(),
gets(), fscanf(), or scanf() using stream that
returns data not supplied by a prior call to ungetc().
Upon successful completion, gets() shall return s. If the stream
is at end-of-file, the end-of-file indicator for the stream shall be set and
gets() shall return a null pointer. If a read error occurs, the error
indicator for the stream shall be set, gets() shall return a null
pointer, and set errno to indicate the error.
Reading a line that overflows the array pointed to by s results in
undefined behavior. The use of fgets() is recommended.
Since the user cannot specify the length of the buffer passed to gets(),
use of this function is discouraged. The length of the string read is
unlimited. It is possible to overflow this buffer in such a way as to cause
applications to fail, or possible system security violations.
It is recommended that the fgets() function should be used to read input
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html