[apple/libc.git] / stdio / fgets.3

.\" Copyright (c) 1990, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" Chris Torek and the American National Standards Committee X3,
.\" on Information Processing Systems.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     @(#)fgets.3	8.1 (Berkeley) 6/4/93
.\" $FreeBSD: src/lib/libc/stdio/fgets.3,v 1.12 2001/10/01 16:08:59 ru Exp $
.\"
.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
.In 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.
.Pp
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
.Bl -tag -width Er
.It Bq Er EBADF
The given
.Fa stream
is not a readable stream.
.El
.Pp
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 .
.Pp
The function
.Fn gets
may also fail and set
.Va errno
for any of the errors specified for the routine
.Xr getchar 3 .
.Sh SEE ALSO
.Xr feof 3 ,
.Xr ferror 3 ,
.Xr fgetln 3
.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 .
Commit	Line	Data
5b2abdfb A	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: src/lib/libc/stdio/fgets.3,v 1.12 2001/10/01 16:08:59 ru Exp $
	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 str" "int size" "FILE stream"
	52	.Ft char *
	53	.Fn gets "char *str"
	54	.Sh DESCRIPTION
	55	The
	56	.Fn fgets
	57	function
	58	reads at most one less than the number of characters specified by
	59	.Fa size
	60	from the given
	61	.Fa stream
	62	and stores them in the string
	63	.Fa str .
	64	Reading stops when a newline character is found,
65	at end-of-file or error.
66	The newline, if any, is retained.
67	If any characters are read and there is no error, a
68	.Ql \e0
69	character is appended to end the string.
70	.Pp
71	The
72	.Fn gets
73	function
74	is equivalent to
75	.Fn fgets
76	with an infinite
77	.Fa size
78	and a
79	.Fa stream
80	of
81	.Em stdin ,
82	except that the newline character (if any) is not stored in the string.
83	It is the caller's responsibility to ensure that the input line,
84	if any, is sufficiently short to fit in the string.
85	.Sh RETURN VALUES
86	Upon successful completion,
87	.Fn fgets
88	and
89	.Fn gets
90	return
91	a pointer to the string.
92	If end-of-file occurs before any characters are read,
93	they return
94	.Dv NULL
95	and the buffer contents is unchanged.
96	If an error occurs,
97	they return
98	.Dv NULL
99	and the buffer contents is indeterminate.
100	The
101	.Fn fgets
102	and
103	.Fn gets
104	functions
105	do not distinguish between end-of-file and error, and callers must use
106	.Xr feof 3
107	and
108	.Xr ferror 3
109	to determine which occurred.
110	.Sh ERRORS
111	.Bl -tag -width Er
112	.It Bq Er EBADF
113	The given
114	.Fa stream
115	is not a readable stream.
116	.El
117	.Pp
118	The function
119	.Fn fgets
120	may also fail and set
121	.Va errno
122	for any of the errors specified for the routines
123	.Xr fflush 3 ,
124	.Xr fstat 2 ,
125	.Xr read 2 ,
126	or
127	.Xr malloc 3 .
128	.Pp
129	The function
130	.Fn gets
131	may also fail and set
132	.Va errno
133	for any of the errors specified for the routine
134	.Xr getchar 3 .
135	.Sh SEE ALSO
136	.Xr feof 3 ,
137	.Xr ferror 3 ,
138	.Xr fgetln 3
139	.Sh STANDARDS
140	The functions
141	.Fn fgets
142	and
143	.Fn gets
144	conform to
145	.St -isoC .
146	.Sh BUGS
147	Since it is usually impossible to ensure that the next input line
148	is less than some arbitrary length, and because overflowing the
149	input buffer is almost invariably a security violation, programs
150	should
151	.Em NEVER
152	use
153	.Fn gets .
154	The
155	.Fn gets
156	function
157	exists purely to conform to
158	.St -isoC .