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 January 10, 2003 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). 96If the main function returns to its original caller, or 97the 98.Xr exit 3 99function is called, all open files are closed (hence all output 100streams are flushed) before program termination. 101Other methods 102of program termination may not close files properly and hence 103buffered output may be lost. 104In particular, 105.Xr _exit 2 106does not flush stdio files. 107Neither does an exit due to a signal. 108Buffers are flushed by 109.Xr abort 3 110as required by POSIX, although previous implementations did not. 111.Pp 112This implementation makes no distinction between 113.Dq text 114and 115.Dq binary 116streams. 117In effect, all streams are binary. 118No translation is performed and no extra padding appears on any stream. 119.Pp 120At program startup, three streams are predefined and need not be 121opened explicitly: 122.Bl -bullet -compact -offset indent 123.It 124.Em standard input 125(for reading conventional input), 126.It 127.Em standard output 128(for writing conventional output), and 129.It 130.Em standard error 131(for writing diagnostic output). 132.El 133These streams are abbreviated 134.Dv stdin , stdout 135and 136.Dv stderr . 137Initially, the standard error stream 138is unbuffered; the standard input and output streams are 139fully buffered if and only if the streams do not refer to 140an interactive or 141.Dq terminal 142device, as determined by the 143.Xr isatty 3 144function. 145In fact, 146.Em all 147freshly-opened streams that refer to terminal devices 148default to line buffering, and 149pending output to such streams is written automatically 150whenever such an input stream is read. 151Note that this applies only to 152.Dq "true reads" ; 153if the read request can be satisfied by existing buffered data, 154no automatic flush will occur. 155In these cases, 156or when a large amount of computation is done after printing 157part of a line on an output terminal, it is necessary to 158.Xr fflush 3 159the standard output before going off and computing so that the output 160will appear. 161Alternatively, these defaults may be modified via the 162.Xr setvbuf 3 163function. 164.Pp 165The 166.Nm 167library is a part of the library 168.Nm libc 169and routines are automatically loaded as needed by the C compiler. 170The 171.Tn SYNOPSIS 172sections of the following manual pages indicate which include files 173are to be used, what the compiler declaration for the function 174looks like and which external variables are of interest. 175.Pp 176The following are defined as macros; 177these names may not be re-used 178without first removing their current definitions with 179.Ic #undef : 180.Dv BUFSIZ , 181.Dv EOF , 182.Dv FILENAME_MAX , 183.Dv FOPEN_MAX , 184.Dv L_ctermid , 185.Dv L_cuserid , 186.Dv L_tmpnam , 187.Dv NULL , 188.Dv P_tmpdir , 189.Dv SEEK_CUR , 190.Dv SEEK_END , 191.Dv SEEK_SET , 192.Dv TMP_MAX , 193.Dv clearerr , 194.Dv clearerr_unlocked , 195.Dv feof , 196.Dv feof_unlocked , 197.Dv ferror , 198.Dv ferror_unlocked , 199.Dv fileno , 200.Dv fileno_unlocked , 201.Dv fropen , 202.Dv fwopen , 203.Dv getc , 204.Dv getc_unlocked , 205.Dv getchar , 206.Dv getchar_unlocked , 207.Dv putc , 208.Dv putc_unlocked , 209.Dv putchar , 210.Dv putchar_unlocked , 211.Dv stderr , 212.Dv stdin 213and 214.Dv stdout . 215Function versions of the macro functions 216.Dv clearerr , 217.Dv clearerr_unlocked , 218.Dv feof , 219.Dv feof_unlocked , 220.Dv ferror , 221.Dv ferror_unlocked , 222.Dv fileno , 223.Dv fileno_unlocked , 224.Dv getc , 225.Dv getc_unlocked , 226.Dv getchar , 227.Dv getchar_unlocked , 228.Dv putc , 229.Dv putc_unlocked , 230.Dv putchar , 231and 232.Dv putchar_unlocked 233exist and will be used if the macro 234definitions are explicitly removed. 235.Sh SEE ALSO 236.Xr close 2 , 237.Xr open 2 , 238.Xr read 2 , 239.Xr write 2 240.Sh BUGS 241The standard buffered functions do not interact well with certain other 242library and system functions, especially 243.Xr vfork 2 . 244.Sh STANDARDS 245The 246.Nm 247library conforms to 248.St -isoC-99 . 249.Sh LIST OF FUNCTIONS 250.Bl -column "Description" 251.It Sy "Function Description" 252.It "asprintf formatted output conversion" 253.It "clearerr check and reset stream status" 254.It "fclose close a stream" 255.It "fdopen stream open functions" 256.It "feof check and reset stream status" 257.It "ferror check and reset stream status" 258.It "fflush flush a stream" 259.It "fgetc get next character or word from input stream" 260.It "fgetln get a line from a stream" 261.It "fgetpos reposition a stream" 262.It "fgets get a line from a stream" 263.It "fgetwc get next wide character from input stream" 264.It "fgetws get a line of wide characters from a stream" 265.It "fileno check and reset stream status" 266.It "fopen stream open functions" 267.It "fprintf formatted output conversion" 268.It "fpurge flush a stream" 269.It "fputc output a character or word to a stream" 270.It "fputs output a line to a stream" 271.It "fputwc output a wide character to a stream" 272.It "fputws output a line of wide characters to a stream" 273.It "fread binary stream input/output" 274.It "freopen stream open functions" 275.It "fropen open a stream" 276.It "fscanf input format conversion" 277.It "fseek reposition a stream" 278.It "fsetpos reposition a stream" 279.It "ftell reposition a stream" 280.It "funopen open a stream" 281.It "fwide set/get orientation of stream" 282.It "fwopen open a stream" 283.It "fwprintf formatted wide character output conversion" 284.It "fwrite binary stream input/output" 285.It "getc get next character or word from input stream" 286.It "getchar get next character or word from input stream" 287.It "gets get a line from a stream" 288.It "getw get next character or word from input stream" 289.It "getwc get next wide character from input stream" 290.It "getwchar get next wide character from input stream" 291.It "mkdtemp create unique temporary directory" 292.It "mkstemp create unique temporary file" 293.It "mktemp create unique temporary file" 294.It "perror system error messages" 295.It "printf formatted output conversion" 296.It "putc output a character or word to a stream" 297.It "putchar output a character or word to a stream" 298.It "puts output a line to a stream" 299.It "putw output a character or word to a stream" 300.It "putwc output a wide character to a stream" 301.It "putwchar output a wide character to a stream" 302.It "remove remove directory entry" 303.It "rewind reposition a stream" 304.It "scanf input format conversion" 305.It "setbuf stream buffering operations" 306.It "setbuffer stream buffering operations" 307.It "setlinebuf stream buffering operations" 308.It "setvbuf stream buffering operations" 309.It "snprintf formatted output conversion" 310.It "sprintf formatted output conversion" 311.It "sscanf input format conversion" 312.It "strerror system error messages" 313.It "swprintf formatted wide character output conversion" 314.It "sys_errlist system error messages" 315.It "sys_nerr system error messages" 316.It "tempnam temporary file routines" 317.It "tmpfile temporary file routines" 318.It "tmpnam temporary file routines" 319.It "ungetc un-get character from input stream" 320.It "ungetwc un-get wide character from input stream" 321.It "vasprintf formatted output conversion" 322.It "vfprintf formatted output conversion" 323.It "vfscanf input format conversion" 324.It "vfwprintf formatted wide character output conversion" 325.It "vprintf formatted output conversion" 326.It "vscanf input format conversion" 327.It "vsnprintf formatted output conversion" 328.It "vsprintf formatted output conversion" 329.It "vsscanf input format conversion" 330.It "vswprintf formatted wide character output conversion" 331.It "vwprintf formatted wide character output conversion" 332.It "wprintf formatted wide character output conversion" 333.El 334