FGETS(3)						   BSD Library Functions Manual 						  FGETS(3)

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, and a '' charac-
     ter 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 or an error occurs before any characters are
     read, they return NULL.  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).

SEE ALSO

     feof(3), ferror(3), fgetln(3)

STANDARDS

     The functions fgets() and gets() conform to ANSI X3.159-1989 (``ANSI C89'') and IEEE Std 1003.1-2001 (``POSIX.1'').  The IEEE Std 1003.1-2008
     (``POSIX.1'') revision marked gets() as obsolescent.

CAVEATS

     The following bit of code illustrates a case where the programmer assumes a string is too long if it does not contain a newline:

	     char buf[1024], *p;

	     while (fgets(buf, sizeof(buf), fp) != NULL) {
		     if ((p = strchr(buf, '
')) == NULL) {
			     fprintf(stderr, "input line too long.
");
			     exit(1);
		     }
		     *p = '';
		     printf("%s
", buf);
	     }

     While the error would be true if a line longer than 1023 characters were read, it would be false in two other cases:

	   1.	If the last line in a file does not contain a newline, the string returned by fgets() will not contain a newline either.  Thus
		strchr() will return NULL and the program will terminate, even if the line was valid.

	   2.	All C string functions, including strchr(), correctly assume the end of the string is represented by a null ('') character.  If
		the first character of a line returned by fgets() were null, strchr() would immediately return without considering the rest of the
		returned text which may indeed include a newline.

     Consider using fgetln(3) instead when dealing with untrusted input.

SECURITY CONSIDERATIONS

     Since it is usually impossible to ensure that the next input line is less than some arbitrary length, and because overflowing the input buf-
     fer is almost invariably a security violation, programs should NEVER use gets().  The gets() function exists purely to conform to ANSI
     X3.159-1989 (``ANSI C89'').

BSD
								   May 13, 2010 							       BSD