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 4.10 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
       https://www.kernel.org/doc/man-pages/.



				  2001-12-26			      STDIO(3)