Man Linux: Main Page and Category List


       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 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

       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 3.24 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at