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.\" @(#)fopen.3 8.1 (Berkeley) 6/4/93 37.\" $FreeBSD: src/lib/libc/stdio/fopen.3,v 1.7.2.6 2001/12/14 18:33:57 ru Exp $ 38.\" $DragonFly: src/lib/libc/stdio/fopen.3,v 1.3 2004/06/08 00:45:00 hmp Exp $ 39.\" 40.Dd June 08, 2004 41.Dt FOPEN 3 42.Os 43.Sh NAME 44.Nm fopen , 45.Nm fdopen , 46.Nm freopen 47.Nd stream open functions 48.Sh LIBRARY 49.Lb libc 50.Sh SYNOPSIS 51.In stdio.h 52.Ft FILE * 53.Fn fopen "const char *path" "const char *mode" 54.Ft FILE * 55.Fn fdopen "int fildes" "const char *mode" 56.Ft FILE * 57.Fn freopen "const char *path" "const char *mode" "FILE *stream" 58.Sh DESCRIPTION 59The 60.Fn fopen 61function 62opens the file whose name is the string pointed to by 63.Fa path 64and associates a stream with it. 65.Pp 66The argument 67.Fa mode 68points to a string beginning with one of the following 69sequences (Additional characters may follow these sequences.): 70.Bl -tag -width indent 71.It Dq Li r 72Open text file for reading. 73The stream is positioned at the beginning of the file. 74.It Dq Li r+ 75Open for reading and writing. 76The stream is positioned at the beginning of the file. 77.It Dq Li w 78Truncate file to zero length or create text file for writing. 79The stream is positioned at the beginning of the file. 80.It Dq Li w+ 81Open for reading and writing. 82The file is created if it does not exist, otherwise it is truncated. 83The stream is positioned at the beginning of the file. 84.It Dq Li a 85Open for writing. 86The file is created if it does not exist. 87The stream is positioned at the end of the file. 88Subsequent writes to the file will always end up at the then current 89end of file, irrespective of any intervening 90.Xr fseek 3 91or similar. 92.It Dq Li a+ 93Open for reading and writing. 94The file is created if it does not exist. 95The stream is positioned at the end of the file. 96Subsequent writes to the file will always end up at the then current 97end of file, irrespective of any intervening 98.Xr fseek 3 99or similar. 100.El 101.Pp 102The 103.Fa mode 104string can also include the letter ``b'' either as a third character or 105as a character between the characters in any of the two-character strings 106described above. 107This is strictly for compatibility with 108.St -isoC 109and has no effect; the ``b'' is ignored. 110.Pp 111Any created files will have mode 112.Pf \\*q Dv S_IRUSR 113\&| 114.Dv S_IWUSR 115\&| 116.Dv S_IRGRP 117\&| 118.Dv S_IWGRP 119\&| 120.Dv S_IROTH 121\&| 122.Dv S_IWOTH Ns \\*q 123.Pq Li 0666 , 124as modified by the process' 125umask value (see 126.Xr umask 2 ) . 127.Pp 128Reads and writes may be intermixed on read/write streams in any order, 129and do not require an intermediate seek as in previous versions of 130.Em stdio . 131This is not portable to other systems, however; 132.Tn ANSI C 133requires that 134a file positioning function intervene between output and input, unless 135an input operation encounters end-of-file. 136.Pp 137The 138.Fn fdopen 139function associates a stream with the existing file descriptor, 140.Fa fildes . 141The mode 142of the stream must be compatible with the mode of the file descriptor. 143When the stream is closed via 144.Xr fclose 3 , 145.Fa fildes 146is closed also. 147.Pp 148The 149.Fn freopen 150function 151opens the file whose name is the string pointed to by 152.Fa path 153and associates the stream pointed to by 154.Fa stream 155with it. 156The original stream (if it exists) is closed. 157The 158.Fa mode 159argument is used just as in the 160.Fn fopen 161function. 162.Pp 163If the 164.Fa path 165argument is 166.Dv NULL , 167.Fn freopen 168attempts to re-open the file associated with 169.Fa stream 170with a new mode. 171The new mode must be compatible with the mode that the stream was originally 172opened with: 173.Bl -bullet -offset indent 174.It 175Streams originally opened with mode 176.Dq Li r 177can only be reopened with that same mode. 178.It 179Streams originally opened with mode 180.Dq Li a 181can be reopened with the same mode, or mode 182.Dq Li w . 183.It 184Streams originally opened with mode 185.Dq Li w 186can be reopened with the same mode, or mode 187.Dq Li a . 188.It 189Streams originally opened with mode 190.Dq Li r+ , 191.Dq Li w+ , 192or 193.Dq Li a+ 194can be reopened with any mode. 195.El 196.Pp 197The primary use of the 198.Fn freopen 199function 200is to change the file associated with a 201standard text stream 202.Dv ( stderr , stdin , 203or 204.Dv stdout ) . 205.Sh RETURN VALUES 206Upon successful completion 207.Fn fopen , 208.Fn fdopen 209and 210.Fn freopen 211return a 212.Tn FILE 213pointer. 214Otherwise, 215.Dv NULL 216is returned and the global variable 217.Va errno 218is set to indicate the error. 219.Sh ERRORS 220.Bl -tag -width Er 221.It Bq Er EINVAL 222The 223.Fa mode 224argument 225to 226.Fn fopen , 227.Fn fdopen , 228or 229.Fn freopen 230was invalid. 231.El 232.Pp 233The 234.Fn fopen , 235.Fn fdopen 236and 237.Fn freopen 238functions 239may also fail and set 240.Va errno 241for any of the errors specified for the routine 242.Xr malloc 3 . 243.Pp 244The 245.Fn fopen 246function 247may also fail and set 248.Va errno 249for any of the errors specified for the routine 250.Xr open 2 . 251.Pp 252The 253.Fn fdopen 254function 255may also fail and set 256.Va errno 257for any of the errors specified for the routine 258.Xr fcntl 2 . 259.Pp 260The 261.Fn freopen 262function 263may also fail and set 264.Va errno 265for any of the errors specified for the routines 266.Xr open 2 , 267.Xr fclose 3 268and 269.Xr fflush 3 . 270.Sh SEE ALSO 271.Xr open 2 , 272.Xr fclose 3 , 273.Xr fileno 3 , 274.Xr fseek 3 , 275.Xr funopen 3 276.Sh STANDARDS 277The 278.Fn fopen 279and 280.Fn freopen 281functions 282conform to 283.St -isoC . 284The 285.Fn fdopen 286function 287conforms to 288.St -p1003.1-88 . 289