1.\" $NetBSD: stdio.3,v 1.6 1998/02/05 18:49:35 perry Exp $ 2.\" 3.\" Copyright (c) 1990, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)stdio.3 8.7 (Berkeley) 4/19/94 35.\" 36.Dd April 19, 1994 37.Dt STDIO 3 38.Os BSD 4 39.Sh NAME 40.Nm stdio 41.Nd standard input/output library functions 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.Fd #include <stdio.h> 46.Fd FILE *stdin; 47.Fd FILE *stdout; 48.Fd FILE *stderr; 49.Sh DESCRIPTION 50The standard 51.Tn I/O 52library provides a simple and efficient buffered stream 53.Tn I/O 54interface. 55Input and output is mapped into logical data streams 56and the physical 57.Tn I/O 58characteristics are concealed. The functions and macros are listed 59below; more information is available from the individual man pages. 60.Pp 61A stream is associated with an external file (which may be a physical 62device) by 63.Em opening 64a file, which may involve creating a new file. Creating an 65existing file causes its former contents to be discarded. 66If a file can support positioning requests (such as a disk file, as opposed 67to a terminal) then a 68.Em file position indicator 69associated with the stream is positioned at the start of the file (byte 70zero), unless the file is opened with append mode. If append mode 71is used, the position indicator will be placed the end-of-file. 72The position indicator is maintained by subsequent reads, writes 73and positioning requests. All input occurs as if the characters 74were read by successive calls to the 75.Xr fgetc 3 76function; all output takes place as if all characters were 77read by successive calls to the 78.Xr fputc 3 79function. 80.Pp 81A file is disassociated from a stream by 82.Em closing 83the file. 84Output streams are flushed (any unwritten buffer contents are transferred 85to the host environment) before the stream is disassociated from the file. 86The value of a pointer to a 87.Dv FILE 88object is indeterminate after a file is closed (garbage). 89.Pp 90A file may be subsequently reopened, by the same or another program 91execution, and its contents reclaimed or modified (if it can be repositioned 92at the start). If the main function returns to its original caller, or 93the 94.Xr exit 3 95function is called, all open files are closed (hence all output 96streams are flushed) before program termination. Other methods 97of program termination, such as 98.Xr abort 3 99do not bother about closing files properly. 100.Pp 101This implementation needs and makes 102no distinction between 103.Dq text 104and 105.Dq binary 106streams. 107In effect, all streams are binary. 108No translation is performed and no extra padding appears on any stream. 109.Pp 110At program startup, three streams are predefined and need not be 111opened explicitly: 112.Bl -bullet -compact -offset indent 113.It 114.Em standard input 115(for reading conventional input), 116.It 117.Em standard output 118(for writing conventional output), and 119.It 120.Em standard error 121(for writing diagnostic output). 122.El 123These streams are abbreviated 124.Em stdin , stdout 125and 126.Em stderr . 127Initially, the standard error stream 128is unbuffered; the standard input and output streams are 129fully buffered if and only if the streams do not refer to 130an interactive or 131.Dq terminal 132device, as determined by the 133.Xr isatty 3 134function. 135In fact, 136.Em all 137freshly-opened streams that refer to terminal devices 138default to line buffering, and 139pending output to such streams is written automatically 140whenever an such an input stream is read. 141Note that this applies only to 142.Dq "true reads" ; 143if the read request can be satisfied by existing buffered data, 144no automatic flush will occur. 145In these cases, 146or when a large amount of computation is done after printing 147part of a line on an output terminal, it is necessary to 148.Xr fflush 3 149the standard output before going off and computing so that the output 150will appear. 151Alternatively, these defaults may be modified via the 152.Xr setvbuf 3 153function. 154.Pp 155The 156.Nm stdio 157library is a part of the library 158.Xr libc 159and routines are automatically loaded as needed by the compilers 160.Xr cc 1 161and 162.Xr pc 1 . 163The 164.Tn SYNOPSIS 165sections of the following manual pages indicate which include files 166are to be used, what the compiler declaration for the function 167looks like and which external variables are of interest. 168.Pp 169The following are defined as macros; 170these names may not be re-used 171without first removing their current definitions with 172.Dv #undef : 173.Dv BUFSIZ , 174.Dv EOF , 175.Dv FILENAME_MAX , 176.Dv FOPEN_MAX , 177.Dv L_cuserid , 178.Dv L_ctermid , 179.Dv L_tmpnam, 180.Dv NULL , 181.Dv SEEK_END , 182.Dv SEEK_SET , 183.Dv SEE_CUR , 184.Dv TMP_MAX , 185.Dv clearerr , 186.Dv feof , 187.Dv ferror , 188.Dv fileno , 189.Dv freopen , 190.Dv fwopen , 191.Dv getc , 192.Dv getchar , 193.Dv putc , 194.Dv putchar , 195.Dv stderr , 196.Dv stdin , 197.Dv stdout . 198Function versions of the macro functions 199.Xr feof , 200.Xr ferror , 201.Xr clearerr , 202.Xr fileno , 203.Xr getc , 204.Xr getchar , 205.Xr putc , 206and 207.Xr putchar 208exist and will be used if the macros 209definitions are explicitly removed. 210.Sh SEE ALSO 211.Xr open 2 , 212.Xr close 2 , 213.Xr read 2 , 214.Xr write 2 215.Sh BUGS 216The standard buffered functions do not interact well with certain other 217library and system functions, especially 218.Xr vfork 219and 220.Xr abort . 221.Sh STANDARDS 222The 223.Nm stdio 224library conforms to 225.St -ansiC . 226.Sh LIST OF FUNCTIONS 227.Bl -column "Description" 228.Sy Function Description 229clearerr check and reset stream status 230fclose close a stream 231fdopen stream open functions 232feof check and reset stream status 233ferror check and reset stream status 234fflush flush a stream 235fgetc get next character or word from input stream 236fgetln get a line from a stream 237fgetpos reposition a stream 238fgets get a line from a stream 239fileno check and reset stream status 240fopen stream open functions 241fprintf formatted output conversion 242fpurge flush a stream 243fputc output a character or word to a stream 244fputs output a line to a stream 245fread binary stream input/output 246freopen stream open functions 247fropen open a stream 248fscanf input format conversion 249fseek reposition a stream 250fsetpos reposition a stream 251ftell reposition a stream 252funopen open a stream 253fwopen open a stream 254fwrite binary stream input/output 255getc get next character or word from input stream 256getchar get next character or word from input stream 257gets get a line from a stream 258getw get next character or word from input stream 259mkstemp create unique temporary file 260mktemp create unique temporary file 261perror system error messages 262printf formatted output conversion 263putc output a character or word to a stream 264putchar output a character or word to a stream 265puts output a line to a stream 266putw output a character or word to a stream 267remove remove directory entry 268rewind reposition a stream 269scanf input format conversion 270setbuf stream buffering operations 271setbuffer stream buffering operations 272setlinebuf stream buffering operations 273setvbuf stream buffering operations 274snprintf formatted output conversion 275sprintf formatted output conversion 276sscanf input format conversion 277strerror system error messages 278sys_errlist system error messages 279sys_nerr system error messages 280tempnam temporary file routines 281tmpfile temporary file routines 282tmpnam temporary file routines 283ungetc un-get character from input stream 284vfprintf formatted output conversion 285vfscanf input format conversion 286vprintf formatted output conversion 287vscanf input format conversion 288vsnprintf formatted output conversion 289vsprintf formatted output conversion 290vsscanf input format conversion 291.El 292