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 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  succes-
       sive 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 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 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 3.27 of the Linux man-pages project.  A description of the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.

								    2001-12-26								  STDIO(3)