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 38.Sh NAME 39.Nm stdio 40.Nd standard input/output library functions 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.In stdio.h 45.Vt FILE *stdin ; 46.Vt FILE *stdout ; 47.Vt FILE *stderr ; 48.Sh DESCRIPTION 49The standard 50.Tn I/O 51library provides a simple and efficient buffered stream 52.Tn I/O 53interface. 54Input and output is mapped into logical data streams 55and the physical 56.Tn I/O 57characteristics are concealed. 58The 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. 65Creating an 66existing file causes its former contents to be discarded. 67If a file can support positioning requests (such as a disk file, as opposed 68to a terminal) then a 69.Em file position indicator 70associated with the stream is positioned at the start of the file (byte 71zero), unless the file is opened with append mode. 72If append mode 73is used, the position indicator will be placed at the end-of-file. 74The position indicator is maintained by subsequent reads, writes 75and positioning requests. 76All input occurs as if the characters 77were read by successive calls to the 78.Xr fgetc 3 79function; all output takes place as if all characters were 80written by successive calls to the 81.Xr fputc 3 82function. 83.Pp 84A file is disassociated from a stream by 85.Em closing 86the file. 87Output streams are flushed (any unwritten buffer contents are transferred 88to the host environment) before the stream is disassociated from the file. 89The value of a pointer to a 90.Dv FILE 91object is indeterminate (garbage) after a file is closed. 92.Pp 93A file may be subsequently reopened, by the same or another program 94execution, and its contents reclaimed or modified (if it can be repositioned 95at the start). If the main function returns to its original caller, or 96the 97.Xr exit 3 98function is called, all open files are closed (hence all output 99streams are flushed) before program termination. Other methods 100of program termination may not close files properly and hence 101buffered output may be lost. In particular, 102.Xr _exit 2 103does not flush stdio files. Neither does an exit due to a signal. 104Buffers are flushed by 105.Xr abort 3 106as required by POSIX, although previous implementations did not. 107.Pp 108This implementation makes no distinction between 109.Dq text 110and 111.Dq binary 112streams. 113In effect, all streams are binary. 114No translation is performed and no extra padding appears on any stream. 115.Pp 116At program startup, three streams are predefined and need not be 117opened explicitly: 118.Bl -bullet -compact -offset indent 119.It 120.Em standard input 121(for reading conventional input), 122.It 123.Em standard output 124(for writing conventional output), and 125.It 126.Em standard error 127(for writing diagnostic output). 128.El 129These streams are abbreviated 130.Em stdin , stdout 131and 132.Em stderr . 133Initially, the standard error stream 134is unbuffered; the standard input and output streams are 135fully buffered if and only if the streams do not refer to 136an interactive or 137.Dq terminal 138device, as determined by the 139.Xr isatty 3 140function. 141In fact, 142.Em all 143freshly-opened streams that refer to terminal devices 144default to line buffering, and 145pending output to such streams is written automatically 146whenever such an input stream is read. 147Note that this applies only to 148.Dq "true reads" ; 149if the read request can be satisfied by existing buffered data, 150no automatic flush will occur. 151In these cases, 152or when a large amount of computation is done after printing 153part of a line on an output terminal, it is necessary to 154.Xr fflush 3 155the standard output before going off and computing so that the output 156will appear. 157Alternatively, these defaults may be modified via the 158.Xr setvbuf 3 159function. 160.Pp 161The 162.Nm 163library is a part of the library 164.Nm libc 165and routines are automatically loaded as needed by the C compiler. 166The 167.Tn SYNOPSIS 168sections of the following manual pages indicate which include files 169are to be used, what the compiler declaration for the function 170looks like and which external variables are of interest. 171.Pp 172The following are defined as macros; 173these names may not be re-used 174without first removing their current definitions with 175.Dv #undef : 176.Dv BUFSIZ , 177.Dv EOF , 178.Dv FILENAME_MAX , 179.Dv FOPEN_MAX , 180.Dv L_cuserid , 181.Dv L_ctermid , 182.Dv L_tmpnam , 183.Dv NULL , 184.Dv P_tmpdir , 185.Dv SEEK_CUR , 186.Dv SEEK_END , 187.Dv SEEK_SET , 188.Dv TMP_MAX , 189.Dv clearerr , 190.Dv feof , 191.Dv ferror , 192.Dv fileno , 193.Dv fropen , 194.Dv fwopen , 195.Dv getc , 196.Dv getchar , 197.Dv putc , 198.Dv putchar , 199.Dv stderr , 200.Dv stdin , 201.Dv stdout , 202.Dv vfscanf . 203Function versions of the macro functions 204.Fn clearerr , 205.Fn feof , 206.Fn ferror , 207.Fn fileno , 208.Fn getc , 209.Fn getchar , 210.Fn putc , 211and 212.Fn putchar 213exist and will be used if the macro 214definitions are explicitly removed. 215.Sh SEE ALSO 216.Xr close 2 , 217.Xr open 2 , 218.Xr read 2 , 219.Xr write 2 220.Sh BUGS 221The standard buffered functions do not interact well with certain other 222library and system functions, especially 223.Xr vfork 2 . 224.Sh STANDARDS 225The 226.Nm 227library conforms to 228.St -isoC . 229.Sh LIST OF FUNCTIONS 230.Bl -column "Description" 231.It Sy "Function Description" 232.It "asprintf formatted output conversion" 233.It "clearerr check and reset stream status" 234.It "fclose close a stream" 235.It "fdopen stream open functions" 236.It "feof check and reset stream status" 237.It "ferror check and reset stream status" 238.It "fflush flush a stream" 239.It "fgetc get next character or word from input stream" 240.It "fgetln get a line from a stream" 241.It "fgetpos reposition a stream" 242.It "fgets get a line from a stream" 243.It "fileno check and reset stream status" 244.It "fopen stream open functions" 245.It "fprintf formatted output conversion" 246.It "fpurge flush a stream" 247.It "fputc output a character or word to a stream" 248.It "fputs output a line to a stream" 249.It "fread binary stream input/output" 250.It "freopen stream open functions" 251.It "fropen open a stream" 252.It "fscanf input format conversion" 253.It "fseek reposition a stream" 254.It "fsetpos reposition a stream" 255.It "ftell reposition a stream" 256.It "funopen open a stream" 257.It "fwopen open a stream" 258.It "fwrite binary stream input/output" 259.It "getc get next character or word from input stream" 260.It "getchar get next character or word from input stream" 261.It "gets get a line from a stream" 262.It "getw get next character or word from input stream" 263.It "mkdtemp create unique temporary file" 264.It "mkstemp create unique temporary file" 265.It "mktemp create unique temporary file" 266.It "perror system error messages" 267.It "printf formatted output conversion" 268.It "putc output a character or word to a stream" 269.It "putchar output a character or word to a stream" 270.It "puts output a line to a stream" 271.It "putw output a character or word to a stream" 272.It "remove remove directory entry" 273.It "rewind reposition a stream" 274.It "scanf input format conversion" 275.It "setbuf stream buffering operations" 276.It "setbuffer stream buffering operations" 277.It "setlinebuf stream buffering operations" 278.It "setvbuf stream buffering operations" 279.It "snprintf formatted output conversion" 280.It "sprintf formatted output conversion" 281.It "sscanf input format conversion" 282.It "strerror system error messages" 283.It "sys_errlist system error messages" 284.It "sys_nerr system error messages" 285.It "tempnam temporary file routines" 286.It "tmpfile temporary file routines" 287.It "tmpnam temporary file routines" 288.It "ungetc un-get character from input stream" 289.It "vasprintf formatted output conversion" 290.It "vfprintf formatted output conversion" 291.It "vfscanf input format conversion" 292.It "vprintf formatted output conversion" 293.It "vscanf input format conversion" 294.It "vsnprintf formatted output conversion" 295.It "vsprintf formatted output conversion" 296.It "vsscanf input format conversion" 297.El 298