STDIO(3)                NetBSD Library Functions Manual               STDIO(3)

NAME
     stdio -- standard input/output library functions

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <stdio.h>

     FILE *stdin;
     FILE *stdout;
     FILE *stderr;

DESCRIPTION
     The standard I/O library provides a simple and efficient buffered stream
     I/O interface.  Input and output is mapped into logical data streams and
     the physical I/O characteristics are concealed.

     A stream is associated with an external file (which may be a physical
     device) by opening a file, which may involve creating a new file.  Creat-
     ing an existing file causes its former contents to be discarded.  If a
     file can support positioning requests (such as a disk file, as opposed to
     a terminal) then a file position indicator associated with the stream is
     positioned at the start of the file (byte zero), unless the file is
     opened with append mode.  If append mode is used, the position indicator
     will be placed the end-of-file.  The position indicator is maintained by
     subsequent reads, writes and positioning requests.  All input occurs as
     if the characters were read by successive calls to the fgetc(3) function;
     all output takes place as if all characters were read by successive calls
     to the fputc(3) function.

     A file is disassociated from a stream by closing the file.  Output
     streams are flushed (any unwritten buffer contents are transferred to the
     host environment) before the stream is disassociated from the file.  The
     value of a pointer to a FILE object is indeterminate after a file is
     closed (garbage).

     A file may be subsequently reopened, by the same or another program exe-
     cution, and its contents reclaimed or modified (if it can be repositioned
     at the start).  If the main function returns to its original caller, or
     the exit(3) function is called, all open files are closed (hence all out-
     put streams are flushed) before program termination.  Other methods of
     program termination, such as abort(3) do not bother about closing files
     properly.

     This implementation needs and makes no distinction between ``text'' and
     ``binary'' streams.  In effect, all streams are binary.  No translation
     is performed and no extra padding appears on any stream.

     At program startup, three streams are predefined and need not be opened
     explicitly:

           1.   standard input for reading conventional input,

           2.   standard output for writing conventional output, and

           3.   standard error for writing diagnostic output.

     These streams are abbreviated stdin, stdout, and stderr.

     Initially, the standard error stream is unbuffered; the standard input
     and output streams are fully buffered if and only if the streams do not
     refer to an interactive or ``terminal'' device, as determined by the
     isatty(3) function.  In fact, all freshly-opened streams that refer to
     terminal devices default to line buffering, and pending output to such
     streams is written automatically whenever an such an input stream is
     read.  Note that this applies only to ``true reads''; if the read request
     can be satisfied by existing buffered data, no automatic flush will
     occur.  In these cases, or when a large amount of computation is done
     after printing part of a line on an output terminal, it is necessary to
     fflush(3) the standard output before going off and computing so that the
     output will appear.  Alternatively, these defaults may be modified via
     the setvbuf(3) function.

IMPLEMENTATION NOTES
     In multi-threaded applications, operations on streams perform implicit
     locking, except for the getc_unlocked(), getchar_unlocked(),
     putc_unlocked(), and putchar_unlocked() functions.  Explicit control of
     stream locking is available through the flockfile(), ftrylockfile(), and
     funlockfile() functions .

     The following are defined as macros; these names may not be re-used with-
     out first removing their current definitions with #undef: BUFSIZ, EOF,
     FILENAME_MAX, FOPEN_MAX, L_cuserid, L_ctermid, L_tmpnam, NULL, SEEK_END,
     SEEK_SET, SEE_CUR, TMP_MAX, clearerr(), feof(), ferror(), fileno(),
     freopen(), fwopen(), getc(), getc_unlocked(), getchar(),
     getchar_unlocked(), putc(), putc_unlocked(), putchar(),
     putchar_unlocked(), stderr, stdin, stdout.

     Function versions of the macro functions feof(), ferror(), clearerr(),
     fileno(), getc(), getc_unlocked(), getchar(), getchar_unlocked(), putc(),
     putc_unlocked(), putchar(), and putchar_unlocked() exist and will be used
     if the macros definitions are explicitly removed.

SEE ALSO
     close(2), open(2), read(2), write(2)

STANDARDS
     The stdio library conforms to ANSI X3.159-1989 (``ANSI C89'').

LIST OF FUNCTIONS
     Function            Description
     clearerr            check and reset stream status
     fclose              close a stream
     fdopen              stream open functions
     feof                check and reset stream status
     ferror              check and reset stream status
     fflush              flush a stream
     fgetc               get next character or word from input stream
     fgetln              get a line from a stream
     fgetpos             reposition a stream
     fgets               get a line from a stream
     fgetwc              get next wide character from input stream
     fileno              check and reset stream status
     flockfile           lock a stream
     fopen               stream open functions
     fprintf             formatted output conversion
     fpurge              flush a stream
     fputc               output a character or word to a stream
     fputs               output a line to a stream
     fputwc              output a wide character to a stream
     fread               binary stream input/output
     freopen             stream open functions
     fropen              open a stream
     fscanf              input format conversion
     fseek               reposition a stream
     fsetpos             reposition a stream
     ftell               reposition a stream
     ftrylockfile        lock a stream (non-blocking)
     funlockfile         unlock a stream
     funopen             open a stream
     fwide               set/get orientation of a stream
     fwopen              open a stream
     fwrite              binary stream input/output
     getc                get next character or word from input stream
     getc_unlocked       get next character or word from input stream
                         (no implicit locking)
     getchar             get next character or word from input stream
     getchar_unlocked    get next character or word from input stream
                         (no implicit locking)
     getdelim            get a delimited record from a stream
     getline             get a line from a stream
     gets                get a line from a stream
     getw                get next character or word from input stream
     getwc               get next wide character from input stream
     getwchar            get next wide character from input stream
     mkstemp             create unique temporary file
     mktemp              create unique temporary file
     perror              system error messages
     printf              formatted output conversion
     putc                output a character or word to a stream
     putc_unlocked       output a character or word to a stream
                         (no implicit locking)
     putchar             output a character or word to a stream
     putchar_unlocked    output a character or word to a stream
                         (no implicit locking)
     puts                output a line to a stream
     putw                output a character or word to a stream
     putwc               output a wide character to a stream
     putwchar            output a wide character to a stream
     remove              remove directory entry
     rewind              reposition a stream
     scanf               input format conversion
     setbuf              stream buffering operations
     setbuffer           stream buffering operations
     setlinebuf          stream buffering operations
     setvbuf             stream buffering operations
     snprintf            formatted output conversion
     sprintf             formatted output conversion
     sscanf              input format conversion
     strerror            system error messages
     sys_errlist         system error messages
     sys_nerr            system error messages
     tempnam             temporary file routines
     tmpfile             temporary file routines
     tmpnam              temporary file routines
     ungetc              un-get character from input stream
     ungetwc             un-get wide character from input stream
     vfprintf            formatted output conversion
     vfscanf             input format conversion
     vprintf             formatted output conversion
     vscanf              input format conversion
     vsnprintf           formatted output conversion
     vsprintf            formatted output conversion
     vsscanf             input format conversion

BUGS
     The standard buffered functions do not interact well with certain other
     library and system functions, especially vfork(2) and abort(3).

NetBSD 6.1.3                      May 5, 2010                     NetBSD 6.1.3

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