1.\" Copyright (c) 1990, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" This code is derived from software contributed to Berkeley by 5.\" Chris Torek and the American National Standards Committee X3, 6.\" on Information Processing Systems. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. All advertising materials mentioning features or use of this software 17.\" must display the following acknowledgement: 18.\" This product includes software developed by the University of 19.\" California, Berkeley and its contributors. 20.\" 4. Neither the name of the University nor the names of its contributors 21.\" may be used to endorse or promote products derived from this software 22.\" without specific prior written permission. 23.\" 24.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34.\" SUCH DAMAGE. 35.\" 36.\" @(#)fgets.3 8.1 (Berkeley) 6/4/93 37.\" $FreeBSD$ 38.\" 39.Dd June 4, 1993 40.Dt FGETS 3 41.Os 42.Sh NAME 43.Nm fgets , 44.Nm gets 45.Nd get a line from a stream 46.Sh LIBRARY 47.Lb libc 48.Sh SYNOPSIS 49.In stdio.h 50.Ft char * 51.Fn fgets "char * restrict str" "int size" "FILE * restrict stream" 52.Ft char * 53.Fn gets "char *str" 54.Sh DESCRIPTION 55The 56.Fn fgets 57function 58reads at most one less than the number of characters specified by 59.Fa size 60from the given 61.Fa stream 62and stores them in the string 63.Fa str . 64Reading stops when a newline character is found, 65at end-of-file or error. 66The newline, if any, is retained. 67If any characters are read and there is no error, a 68.Ql \e0 69character is appended to end the string. 70.Pp 71The 72.Fn gets 73function 74is equivalent to 75.Fn fgets 76with an infinite 77.Fa size 78and a 79.Fa stream 80of 81.Dv stdin , 82except that the newline character (if any) is not stored in the string. 83It is the caller's responsibility to ensure that the input line, 84if any, is sufficiently short to fit in the string. 85.Sh RETURN VALUES 86Upon successful completion, 87.Fn fgets 88and 89.Fn gets 90return 91a pointer to the string. 92If end-of-file occurs before any characters are read, 93they return 94.Dv NULL 95and the buffer contents remain unchanged. 96If an error occurs, 97they return 98.Dv NULL 99and the buffer contents are indeterminate. 100The 101.Fn fgets 102and 103.Fn gets 104functions 105do not distinguish between end-of-file and error, and callers must use 106.Xr feof 3 107and 108.Xr ferror 3 109to determine which occurred. 110.Sh ERRORS 111.Bl -tag -width Er 112.It Bq Er EBADF 113The given 114.Fa stream 115is not a readable stream. 116.El 117.Pp 118The function 119.Fn fgets 120may also fail and set 121.Va errno 122for any of the errors specified for the routines 123.Xr fflush 3 , 124.Xr fstat 2 , 125.Xr read 2 , 126or 127.Xr malloc 3 . 128.Pp 129The function 130.Fn gets 131may also fail and set 132.Va errno 133for any of the errors specified for the routine 134.Xr getchar 3 . 135.Sh SECURITY CONSIDERATIONS 136The 137.Fn gets 138function cannot be used securely. 139Because of its lack of bounds checking, 140and the inability for the calling program 141to reliably determine the length of the next incoming line, 142the use of this function enables malicious users 143to arbitrarily change a running program's functionality through 144a buffer overflow attack. 145It is strongly suggested that the 146.Fn fgets 147function be used in all cases. 148(See 149the FSA.) 150.Sh SEE ALSO 151.Xr feof 3 , 152.Xr ferror 3 , 153.Xr fgetln 3 , 154.Xr fgetws 3 155.Rs 156.%T "The FreeBSD Security Architecture" 157.Re 158(See 159.Pa /usr/share/doc/{to be determined} . ) 160.Sh STANDARDS 161The functions 162.Fn fgets 163and 164.Fn gets 165conform to 166.St -isoC-99 . 167