1.\" Copyright (c) 1990, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)stdio.3 8.7 (Berkeley) 4/19/94 33.\" $FreeBSD$ 34.\" 35.Dd April 19, 1994 36.Dt STDIO 3 37.Os BSD 4 38.Sh NAME 39.Nm stdio 40.Nd standard input/output library functions 41.Sh SYNOPSIS 42.Fd #include <stdio.h> 43.Fd FILE *stdin; 44.Fd FILE *stdout; 45.Fd FILE *stderr; 46.Sh DESCRIPTION 47The standard 48.Tn I/O 49library provides a simple and efficient buffered stream 50.Tn I/O 51interface. 52Input and output is mapped into logical data streams 53and the physical 54.Tn I/O 55characteristics are concealed. The functions and macros are listed 56below; more information is available from the individual man pages. 57.Pp 58A stream is associated with an external file (which may be a physical 59device) by 60.Em opening 61a file, which may involve creating a new file. Creating an 62existing file causes its former contents to be discarded. 63If a file can support positioning requests (such as a disk file, as opposed 64to a terminal) then a 65.Em file position indicator 66associated with the stream is positioned at the start of the file (byte 67zero), unless the file is opened with append mode. If append mode 68is used, the position indicator will be placed at the end-of-file. 69The position indicator is maintained by subsequent reads, writes 70and positioning requests. All input occurs as if the characters 71were read by successive calls to the 72.Xr fgetc 3 73function; all output takes place as if all characters were 74written by successive calls to the 75.Xr fputc 3 76function. 77.Pp 78A file is disassociated from a stream by 79.Em closing 80the file. 81Output streams are flushed (any unwritten buffer contents are transferred 82to the host environment) before the stream is disassociated from the file. 83The value of a pointer to a 84.Dv FILE 85object is indeterminate (garbage) after a file is closed. 86.Pp 87A file may be subsequently reopened, by the same or another program 88execution, and its contents reclaimed or modified (if it can be repositioned 89at the start). If the main function returns to its original caller, or 90the 91.Xr exit 3 92function is called, all open files are closed (hence all output 93streams are flushed) before program termination. Other methods 94of program termination may not close files properly and hence 95buffered output may be lost. In particular, 96.Xr _exit 2 97does not flush stdio files. Neither does an exit due to a signal. 98Buffers are flushed by 99.Xr abort 3 100as required by POSIX, although previous implementations did not. 101.Pp 102This implementation makes no 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 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.Nm libc 159and routines are automatically loaded as needed by the C compiler. 160The 161.Tn SYNOPSIS 162sections of the following manual pages indicate which include files 163are to be used, what the compiler declaration for the function 164looks like and which external variables are of interest. 165.Pp 166The following are defined as macros; 167these names may not be re-used 168without first removing their current definitions with 169.Dv #undef : 170.Dv BUFSIZ , 171.Dv EOF , 172.Dv FILENAME_MAX , 173.Dv FOPEN_MAX , 174.Dv L_cuserid , 175.Dv L_ctermid , 176.Dv L_tmpnam, 177.Dv NULL , 178.Dv P_tmpdir, 179.Dv SEEK_CUR , 180.Dv SEEK_END , 181.Dv SEEK_SET , 182.Dv TMP_MAX , 183.Dv clearerr , 184.Dv feof , 185.Dv ferror , 186.Dv fileno , 187.Dv fropen , 188.Dv fwopen , 189.Dv getc , 190.Dv getchar , 191.Dv putc , 192.Dv putchar , 193.Dv stderr , 194.Dv stdin , 195.Dv stdout , 196.Dv vfscanf . 197Function versions of the macro functions 198.Fn clearerr , 199.Fn feof , 200.Fn ferror , 201.Fn fileno , 202.Fn getc , 203.Fn getchar , 204.Fn putc , 205and 206.Fn putchar 207exist and will be used if the macro 208definitions are explicitly removed. 209.Sh SEE ALSO 210.Xr close 2 , 211.Xr open 2 , 212.Xr read 2 , 213.Xr write 2 214.Sh BUGS 215The standard buffered functions do not interact well with certain other 216library and system functions, especially 217.Xr vfork 2 . 218.Sh STANDARDS 219The 220.Nm stdio 221library conforms to 222.St -ansiC . 223.Sh LIST OF FUNCTIONS 224.Bl -column "Description" 225.Sy Function Description 226asprintf formatted output conversion 227clearerr check and reset stream status 228fclose close a stream 229fdopen stream open functions 230feof check and reset stream status 231ferror check and reset stream status 232fflush flush a stream 233fgetc get next character or word from input stream 234fgetln get a line from a stream 235fgetpos reposition a stream 236fgets get a line from a stream 237fileno check and reset stream status 238fopen stream open functions 239fprintf formatted output conversion 240fpurge flush a stream 241fputc output a character or word to a stream 242fputs output a line to a stream 243fread binary stream input/output 244freopen stream open functions 245fropen open a stream 246fscanf input format conversion 247fseek reposition a stream 248fsetpos reposition a stream 249ftell reposition a stream 250funopen open a stream 251fwopen open a stream 252fwrite binary stream input/output 253getc get next character or word from input stream 254getchar get next character or word from input stream 255gets get a line from a stream 256getw get next character or word from input stream 257mkdtemp create unique temporary file 258mkstemp create unique temporary file 259mktemp create unique temporary file 260perror system error messages 261printf formatted output conversion 262putc output a character or word to a stream 263putchar output a character or word to a stream 264puts output a line to a stream 265putw output a character or word to a stream 266remove remove directory entry 267rewind reposition a stream 268scanf input format conversion 269setbuf stream buffering operations 270setbuffer stream buffering operations 271setlinebuf stream buffering operations 272setvbuf stream buffering operations 273snprintf formatted output conversion 274sprintf formatted output conversion 275sscanf input format conversion 276strerror system error messages 277sys_errlist system error messages 278sys_nerr system error messages 279tempnam temporary file routines 280tmpfile temporary file routines 281tmpnam temporary file routines 282ungetc un-get character from input stream 283vasprintf formatted output conversion 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