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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, the posi-
       tion 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
       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 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 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
       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 re-used
       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, SEE_CUR, TMP_MAX, clearerr, feof,  ferror,  fileno,
       fropen,  fwopen,  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    check and reset stream status

       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

       fropen    open a stream

       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 file name (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 ANSI X3.159-1989 (``ANSI C'').

SEE ALSO
       open(2), close(2), read(2), write(2), stdout(3)



                                  2001-12-26                          STDIO(3)