NAME
fgets, gets
— get a line from a
stream
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include
<stdio.h>
char *
fgets(char
* restrict str, int
size, FILE * restrict
stream);
char *
gets(char
*str);
DESCRIPTION
The
fgets()
function reads at most one less than the number of characters specified by
size from the given stream and
stores them in the string str. Reading stops when a
newline character is found, at end-of-file or error. The newline, if any, is
retained. If any characters are read and there is no error, a
‘\0’ character is appended to end the
string.
The
gets()
function is equivalent to fgets() with an infinite
size and a stream of
stdin, except that the newline character (if any) is
not stored in the string. It is the caller's responsibility to ensure that
the input line, if any, is sufficiently short to fit in the string.
RETURN VALUES
Upon successful completion, fgets() and
gets() return a pointer to the string. If
end-of-file occurs before any characters are read, they return
NULL and the buffer contents remain unchanged. If an
error occurs, they return NULL and the buffer
contents are indeterminate. The fgets() and
gets() functions do not distinguish between
end-of-file and error, and callers must use
feof(3) and
ferror(3)
to determine which occurred.
ERRORS
- [
EBADF] - The given stream is not a readable stream.
The function fgets() may also fail and set
errno for any of the errors specified for the routines
fflush(3),
fstat(2),
read(2), or
malloc(3).
The function gets() may also fail and set
errno for any of the errors specified for the routine
getchar(3).
SECURITY CONSIDERATIONS
The gets() function cannot be used
securely. Because of its lack of bounds checking, and the inability for the
calling program to reliably determine the length of the next incoming line,
the use of this function enables malicious users to arbitrarily change a
running program's functionality through a buffer overflow attack. It is
strongly suggested that the fgets() function be used
in all cases. (See the FSA.)
SEE ALSO
STANDARDS
The functions fgets() and
gets() conform to ISO/IEC 9899:1999
(“ISO C99”).