stdio - standard input/output library functions


   #include <stdio.h>

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


   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 output), 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 refer to an interactive

   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

   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


   The stdio library conforms to C89.


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


   This  page  is  part of release 4.09 of the Linux man-pages project.  A
   description of the project, information about reporting bugs,  and  the
   latest     version     of     this    page,    can    be    found    at

                              2001-12-26                          STDIO(3)


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