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NAME

       stdio - standard input/output library functions

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.   The functions and macros are listed below; more information is available
       from the individual man pages.

       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.  Creating 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, it is unspecified whether the position indicator will be
       placed at the start or the end of the 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 written 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  execution,  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  output  streams  are flushed) before program termination.  Other
       methods of program termination, such  as  abort(3)  do  not  bother  about  closing  files
       properly.

       At  program  startup, three text streams are predefined and need not be opened explicitly:
       standard input (for reading conventional input), standard output (for writing conventional
       input), and standard error (for writing diagnostic output).  These streams are abbreviated
       stdin,stdout and stderr.  When opened, the standard error stream is  not  fully  buffered;
       the standard input and output streams are fully buffered if and only if the streams do not
       to refer to an interactive device.

       Output streams that refer to terminal devices are always line buffered by default; pending
       output  to such streams is written automatically whenever an input stream that refers to a
       terminal device is read.  In cases where 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.

       The stdio library is a part of the library libc and routines are automatically  loaded  as
       needed  by  the  compilers cc(1) and pc(1).  The SYNOPSIS sections of the following manual
       pages indicate which include files are to be used, what the compiler declaration  for  the
       function looks like and which external variables are of interest.

       The  following are defined as macros; these names may not be reused without first removing
       their current definitions with #undef: BUFSIZ, EOF,  FILENAME_MAX,  FOPEN_MAX,  L_cuserid,
       L_ctermid,  L_tmpnam, NULL, SEEK_END, SEEK_SET, SEEK_CUR, TMP_MAX, clearerr, feof, ferror,
       fileno, getc, getchar, putc, putchar, stderr, stdin, stdout.   Function  versions  of  the
       macro functions feof, ferror, clearerr, fileno, getc, getchar, putc, and putchar exist and
       will be used if the macros definitions are explicitly removed.

   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
       fgetpos       reposition a stream
       fgets         get a line from a stream
       fileno        return the integer descriptor of the argument 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
       fread         binary stream input/output
       freopen       stream open functions
       fscanf        input format conversion
       fseek         reposition a stream
       fsetpos       reposition a stream
       ftell         reposition a stream
       fwrite        binary stream input/output
       getc          get next character or word from input stream
       getchar       get next character or word from input stream
       gets          get a line from a stream
       getw          get next character or word from input stream
       mktemp        make temporary filename (unique)
       perror        system error messages
       printf        formatted output conversion
       putc          output a character or word to a stream
       putchar       output a character or word to a stream
       puts          output a line to a stream
       putw          output a character or word 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
       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
       vfprintf      formatted output conversion
       vfscanf       input format conversion
       vprintf       formatted output conversion
       vscanf        input format conversion
       vsprintf      formatted output conversion
       vsscanf       input format conversion

CONFORMING TO

       The stdio library conforms to C89.

SEE ALSO

       close(2), open(2), read(2), write(2), stdout(3), unlocked_stdio(3)

COLOPHON

       This page is part of release 3.35 of the Linux man-pages project.  A  description  of  the
       project,  and information about reporting bugs, can be found at http://man7.org/linux/man-
       pages/.

                                            2001-12-26                                   STDIO(3)