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@(#)fgets.3 8.1 (Berkeley) 6/4/93
$FreeBSD: head/lib/libc/stdio/fgets.3 88971 2002-01-06 21:16:41Z chris $
.Dd June 4, 1993 .Dt FGETS 3 .Os .Sh NAME .Nm fgets , .Nm gets .Nd get a line from a stream .Sh LIBRARY .Lb libc .Sh SYNOPSIS n stdio.h .Ft char * .Fn fgets "char *str" "int size" "FILE *stream" .Ft char * .Fn gets "char *str" .Sh DESCRIPTION The .Fn fgets function reads at most one less than the number of characters specified by .Fa size from the given .Fa stream and stores them in the string .Fa 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 .Ql \e0 character is appended to end the string.
p The .Fn gets function is equivalent to .Fn fgets with an infinite .Fa size and a .Fa stream of .Em 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. .Sh RETURN VALUES Upon successful completion, .Fn fgets and .Fn gets return a pointer to the string. If end-of-file occurs before any characters are read, they return .Dv NULL and the buffer contents is unchanged. If an error occurs, they return .Dv NULL and the buffer contents is indeterminate. The .Fn fgets and .Fn gets functions do not distinguish between end-of-file and error, and callers must use .Xr feof 3 and .Xr ferror 3 to determine which occurred. .Sh ERRORS l -tag -width Er t Bq Er EBADF The given .Fa stream is not a readable stream. .El
p The function .Fn fgets may also fail and set .Va errno for any of the errors specified for the routines .Xr fflush 3 , .Xr fstat 2 , .Xr read 2 , or .Xr malloc 3 .
p The function .Fn gets may also fail and set .Va errno for any of the errors specified for the routine .Xr getchar 3 . .Sh SECURITY CONSIDERATIONS The .Fn gets function cannot be used securely. Because of its lack of bounds checking, the use of this function enables malicious users to arbitrarily change a running program's functionality through a buffer overflow attack. (See the FSA.) .Sh SEE ALSO .Xr feof 3 , .Xr ferror 3 , .Xr fgetln 3 .Rs .%T "The FreeBSD Security Architecture" .%J "/usr/share/doc/{to be determined}" .Re .Sh STANDARDS The functions .Fn fgets and .Fn gets conform to .St -isoC . .Sh BUGS Since it is usually impossible to ensure that the next input line is less than some arbitrary length, and because overflowing the input buffer is almost invariably a security violation, programs should .Em NEVER use .Fn gets . The .Fn gets function exists purely to conform to .St -isoC .