1.\" $NetBSD: fopen.3,v 1.15 2002/05/15 07:00:22 kleink Exp $ 2.\" 3.\" Copyright (c) 1990, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" This code is derived from software contributed to Berkeley by 7.\" Chris Torek and the American National Standards Committee X3, 8.\" on Information Processing Systems. 9.\" 10.\" Redistribution and use in source and binary forms, with or without 11.\" modification, are permitted provided that the following conditions 12.\" are met: 13.\" 1. Redistributions of source code must retain the above copyright 14.\" notice, this list of conditions and the following disclaimer. 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in the 17.\" documentation and/or other materials provided with the distribution. 18.\" 3. All advertising materials mentioning features or use of this software 19.\" must display the following acknowledgement: 20.\" This product includes software developed by the University of 21.\" California, Berkeley and its contributors. 22.\" 4. Neither the name of the University nor the names of its contributors 23.\" may be used to endorse or promote products derived from this software 24.\" without specific prior written permission. 25.\" 26.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36.\" SUCH DAMAGE. 37.\" 38.\" @(#)fopen.3 8.1 (Berkeley) 6/4/93 39.\" 40.Dd June 4, 1993 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.Fd #include \*[Lt]stdio.h\*[Gt] 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 * restrict 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. 73.It Dq Li r+ 74Open for reading and writing. 75.It Dq Li w 76Truncate file to zero length or create text file for writing. 77.It Dq Li w+ 78Open for reading and writing. 79The file is created if it does not exist, otherwise it is truncated. 80.It Dq Li a 81Append; open for writing. 82The file is created if it does not exist. 83.It Dq Li a+ 84Append; open for reading and writing. 85The file is created if it does not exist. 86.El 87.Pp 88The 89.Fa mode 90string can also include the letter ``b'' either as a last character or 91as a character between the characters in any of the two-character strings 92described above. 93This is strictly for compatibility with 94.St -ansiC 95and has no effect; the ``b'' is ignored. 96.Pp 97The letter ``f'' in the mode string restricts fopen to regular 98files; if the file opened is not a regular file, 99.Fn fopen 100will fail. This is a non 101.St -ansiC 102extension. 103.Pp 104Any created files will have mode 105.Pf \\*q Dv S_IRUSR 106\&| 107.Dv S_IWUSR 108\&| 109.Dv S_IRGRP 110\&| 111.Dv S_IWGRP 112\&| 113.Dv S_IROTH 114\&| 115.Dv S_IWOTH Ns \\*q 116.Pq Li 0666 , 117as modified by the process' 118umask value (see 119.Xr umask 2 ) . 120.Pp 121Opening a file with append mode causes all subsequent writes to it 122to be forced to the then current end of file, regardless of intervening 123repositioning of the stream. 124.Pp 125The 126.Fn fopen 127and 128.Fn freopen 129functions initially position the stream at the start of the file 130unless the file is opened with append mode, 131in which case the stream is initially positioned at the end of the file. 132.\" PR 6072 claims this paragraph is not correct. 133.\" .Pp 134.\" Reads and writes may be intermixed on read/write streams in any order, 135.\" and do not require an intermediate seek as in previous versions of 136.\" .Em stdio . 137.\" This is not portable to other systems, however; 138.\" .Tn ANSI C 139.\" requires that 140.\" a file positioning function intervene between output and input, unless 141.\" an input operation encounters end-of-file. 142.Pp 143The 144.Fn fdopen 145function associates a stream with the existing file descriptor, 146.Fa fildes . 147The 148.Fa mode 149of the stream must be compatible with the mode of the file descriptor. 150The stream is positioned at the file offset of the file descriptor. 151.Pp 152The 153.Fn freopen 154function 155opens the file whose name is the string pointed to by 156.Fa path 157and associates the stream pointed to by 158.Fa stream 159with it. 160The original stream (if it exists) is closed. 161The 162.Fa mode 163argument is used just as in the 164.Fn fopen 165function. 166The primary use of the 167.Fn freopen 168function 169is to change the file associated with a 170standard text stream 171.Pf ( Em stderr , 172.Em stdin , 173or 174.Em stdout ) . 175.Sh RETURN VALUES 176Upon successful completion 177.Fn fopen , 178.Fn fdopen 179and 180.Fn freopen 181return a 182.Tn FILE 183pointer. 184Otherwise, 185.Dv NULL 186is returned and the global variable 187.Va errno 188is set to indicate the error. 189.Sh ERRORS 190.Bl -tag -width Er 191.It Bq Er EINVAL 192The 193.Fa mode 194provided to 195.Fn fopen , 196.Fn fdopen , 197or 198.Fn freopen 199was invalid. 200.It Bq Er EFTYPE 201The file is not a regular file and the character ``f'' is specified 202in the mode. 203.El 204.Pp 205The 206.Fn fopen , 207.Fn fdopen 208and 209.Fn freopen 210functions 211may also fail and set 212.Va errno 213for any of the errors specified for the routine 214.Xr malloc 3 . 215.Pp 216The 217.Fn fopen 218function 219may also fail and set 220.Va errno 221for any of the errors specified for the routine 222.Xr open 2 . 223.Pp 224The 225.Fn fdopen 226function 227may also fail and set 228.Va errno 229for any of the errors specified for the routine 230.Xr fcntl 2 . 231.Pp 232The 233.Fn freopen 234function 235may also fail and set 236.Va errno 237for any of the errors specified for the routines 238.Xr open 2 , 239.Xr fclose 3 240and 241.Xr fflush 3 . 242.Sh SEE ALSO 243.Xr open 2 , 244.Xr fclose 3 , 245.Xr fseek 3 , 246.Xr funopen 3 247.Sh STANDARDS 248The 249.Fn fopen 250and 251.Fn freopen 252functions 253conform to 254.St -ansiC . 255The 256.Fn fdopen 257function conforms to 258.St -p1003.1-90 . 259