stdio

STDIO(3)                   Linux Programmer's Manual                  STDIO(3)

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 func-
       tions 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.  Cre-
       ating  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 subse-
       quent 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 reposi-
       tioned  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
       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 stan-
       dard  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  auto-
       matically  loaded as needed by the compilers cc(1) and pc(1).  The SYN-
       OPSIS 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 4.04 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
       http://www.kernel.org/doc/man-pages/.

                                  2001-12-26                          STDIO(3)
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