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. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)stdio.3 8.7 (Berkeley) 4/19/94 29.\" 30.Dd March 3, 2009 31.Dt STDIO 3 32.Os 33.Sh NAME 34.Nm stdio 35.Nd standard input/output library functions 36.Sh LIBRARY 37.Lb libc 38.Sh SYNOPSIS 39.In stdio.h 40.Vt FILE *stdin ; 41.Vt FILE *stdout ; 42.Vt FILE *stderr ; 43.Sh DESCRIPTION 44The standard 45.Tn I/O 46library provides a simple and efficient buffered stream 47.Tn I/O 48interface. 49Input and output is mapped into logical data streams 50and the physical 51.Tn I/O 52characteristics are concealed. 53The functions and macros are listed 54below; more information is available from the individual man pages. 55.Pp 56A stream is associated with an external file (which may be a physical 57device) by 58.Em opening 59a file, which may involve creating a new file. 60Creating an 61existing file causes its former contents to be discarded. 62If a file can support positioning requests (such as a disk file, as opposed 63to a terminal) then a 64.Em file position indicator 65associated with the stream is positioned at the start of the file (byte 66zero), unless the file is opened with append mode. 67If 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. 71All input occurs as if the characters 72were read by successive calls to the 73.Xr fgetc 3 74function; all output takes place as if all characters were 75written by successive calls to the 76.Xr fputc 3 77function. 78.Pp 79A file is disassociated from a stream by 80.Em closing 81the file. 82Output streams are flushed (any unwritten buffer contents are transferred 83to the host environment) before the stream is disassociated from the file. 84The value of a pointer to a 85.Dv FILE 86object is indeterminate (garbage) after a file is closed. 87.Pp 88A file may be subsequently reopened, by the same or another program 89execution, and its contents reclaimed or modified (if it can be repositioned 90at the start). 91If the main function returns to its original caller, or 92the 93.Xr exit 3 94function is called, all open files are closed (hence all output 95streams are flushed) before program termination. 96Other methods 97of program termination may not close files properly and hence 98buffered output may be lost. 99In particular, 100.Xr _exit 2 101does not flush stdio files. 102Neither does an exit due to a signal. 103Buffers are flushed by 104.Xr abort 3 105as required by POSIX, although previous implementations did not. 106.Pp 107This implementation makes no distinction between 108.Dq text 109and 110.Dq binary 111streams. 112In effect, all streams are binary. 113No translation is performed and no extra padding appears on any stream. 114.Pp 115At program startup, three streams are predefined and need not be 116opened explicitly: 117.Bl -bullet -compact -offset indent 118.It 119.Em standard input 120(for reading conventional input), 121.It 122.Em standard output 123(for writing conventional output), and 124.It 125.Em standard error 126(for writing diagnostic output). 127.El 128These streams are abbreviated 129.Dv stdin , stdout 130and 131.Dv stderr . 132Initially, the standard error stream 133is unbuffered; the standard input and output streams are 134fully buffered if and only if the streams do not refer to 135an interactive or 136.Dq terminal 137device, as determined by the 138.Xr isatty 3 139function. 140In fact, 141.Em all 142freshly-opened streams that refer to terminal devices 143default to line buffering, and 144pending output to such streams is written automatically 145whenever such an input stream is read. 146Note that this applies only to 147.Dq "true reads" ; 148if the read request can be satisfied by existing buffered data, 149no automatic flush will occur. 150In these cases, 151or when a large amount of computation is done after printing 152part of a line on an output terminal, it is necessary to 153.Xr fflush 3 154the standard output before going off and computing so that the output 155will appear. 156Alternatively, these defaults may be modified via the 157.Xr setvbuf 3 158function. 159.Pp 160The 161.Nm 162library is a part of the library 163.Nm libc 164and routines are automatically loaded as needed by the C compiler. 165The 166.Tn SYNOPSIS 167sections of the following manual pages indicate which include files 168are to be used, what the compiler declaration for the function 169looks like and which external variables are of interest. 170.Pp 171The following are defined as macros; 172these names may not be re-used 173without first removing their current definitions with 174.Ic #undef : 175.Dv BUFSIZ , 176.Dv EOF , 177.Dv FILENAME_MAX , 178.Dv FOPEN_MAX , 179.Dv L_ctermid , 180.Dv L_cuserid , 181.Dv L_tmpnam , 182.Dv NULL , 183.Dv P_tmpdir , 184.Dv SEEK_CUR , 185.Dv SEEK_END , 186.Dv SEEK_SET , 187.Dv TMP_MAX , 188.Dv clearerr , 189.Dv clearerr_unlocked , 190.Dv feof , 191.Dv feof_unlocked , 192.Dv ferror , 193.Dv ferror_unlocked , 194.Dv fileno , 195.Dv fileno_unlocked , 196.Dv fropen , 197.Dv fwopen , 198.Dv getc , 199.Dv getc_unlocked , 200.Dv getchar , 201.Dv getchar_unlocked , 202.Dv putc , 203.Dv putc_unlocked , 204.Dv putchar , 205.Dv putchar_unlocked , 206.Dv stderr , 207.Dv stdin 208and 209.Dv stdout . 210Function versions of the macro functions 211.Dv clearerr , 212.Dv clearerr_unlocked , 213.Dv feof , 214.Dv feof_unlocked , 215.Dv ferror , 216.Dv ferror_unlocked , 217.Dv fileno , 218.Dv fileno_unlocked , 219.Dv getc , 220.Dv getc_unlocked , 221.Dv getchar , 222.Dv getchar_unlocked , 223.Dv putc , 224.Dv putc_unlocked , 225.Dv putchar , 226and 227.Dv putchar_unlocked 228exist and will be used if the macro 229definitions are explicitly removed. 230.Sh SEE ALSO 231.Xr close 2 , 232.Xr open 2 , 233.Xr read 2 , 234.Xr write 2 235.Sh STANDARDS 236The 237.Nm 238library conforms to 239.St -isoC-99 . 240.Sh LIST OF FUNCTIONS 241.Bl -column "Description" 242.It Sy "Function Description" 243.It "asprintf formatted output conversion" 244.It "clearerr check and reset stream status" 245.It "dprintf formatted output conversion" 246.It "fclose close a stream" 247.It "fdopen stream open functions" 248.It "feof check and reset stream status" 249.It "ferror check and reset stream status" 250.It "fflush flush a stream" 251.It "fgetc get next character or word from input stream" 252.It "fgetln get a line from a stream" 253.It "fgetpos reposition a stream" 254.It "fgets get a line from a stream" 255.It "fgetwc get next wide character from input stream" 256.It "fgetws get a line of wide characters from a stream" 257.It "fileno check and reset stream status" 258.It "fopen stream open functions" 259.It "fprintf formatted output conversion" 260.It "fpurge flush a stream" 261.It "fputc output a character or word to a stream" 262.It "fputs output a line to a stream" 263.It "fputwc output a wide character to a stream" 264.It "fputws output a line of wide characters to a stream" 265.It "fread binary stream input/output" 266.It "freopen stream open functions" 267.It "fropen open a stream" 268.It "fscanf input format conversion" 269.It "fseek reposition a stream" 270.It "fsetpos reposition a stream" 271.It "ftell reposition a stream" 272.It "funopen open a stream" 273.It "fwide set/get orientation of stream" 274.It "fwopen open a stream" 275.It "fwprintf formatted wide character output conversion" 276.It "fwrite binary stream input/output" 277.It "getc get next character or word from input stream" 278.It "getchar get next character or word from input stream" 279.It "getdelim get a line from a stream" 280.It "getline get a line from a stream" 281.It "getw get next character or word from input stream" 282.It "getwc get next wide character from input stream" 283.It "getwchar get next wide character from input stream" 284.It "mkdtemp create unique temporary directory" 285.It "mkstemp create unique temporary file" 286.It "mktemp create unique temporary file" 287.It "perror system error messages" 288.It "printf formatted output conversion" 289.It "putc output a character or word to a stream" 290.It "putchar output a character or word to a stream" 291.It "puts output a line to a stream" 292.It "putw output a character or word to a stream" 293.It "putwc output a wide character to a stream" 294.It "putwchar output a wide character to a stream" 295.It "remove remove directory entry" 296.It "rewind reposition a stream" 297.It "scanf input format conversion" 298.It "setbuf stream buffering operations" 299.It "setbuffer stream buffering operations" 300.It "setlinebuf stream buffering operations" 301.It "setvbuf stream buffering operations" 302.It "snprintf formatted output conversion" 303.It "sprintf formatted output conversion" 304.It "sscanf input format conversion" 305.It "strerror system error messages" 306.It "swprintf formatted wide character output conversion" 307.It "sys_errlist system error messages" 308.It "sys_nerr system error messages" 309.It "tempnam temporary file routines" 310.It "tmpfile temporary file routines" 311.It "tmpnam temporary file routines" 312.It "ungetc un-get character from input stream" 313.It "ungetwc un-get wide character from input stream" 314.It "vasprintf formatted output conversion" 315.It "vdprintf formatted output conversion" 316.It "vfprintf formatted output conversion" 317.It "vfscanf input format conversion" 318.It "vfwprintf formatted wide character output conversion" 319.It "vprintf formatted output conversion" 320.It "vscanf input format conversion" 321.It "vsnprintf formatted output conversion" 322.It "vsprintf formatted output conversion" 323.It "vsscanf input format conversion" 324.It "vswprintf formatted wide character output conversion" 325.It "vwprintf formatted wide character output conversion" 326.It "wprintf formatted wide character output conversion" 327.El 328.Sh BUGS 329The standard buffered functions do not interact well with certain other 330library and system functions, especially 331.Xr vfork 2 . 332