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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 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
       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 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  cc(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(3)      check and reset stream status
       fclose(3)        close a stream
       fdopen(3)        stream open functions
       feof(3)          check and reset stream status
       ferror(3)        check and reset stream status
       fflush(3)        flush a stream
       fgetc(3)         get next character or word from input stream
       fgetpos(3)       reposition a stream
       fgets(3)         get a line from a stream
       fileno(3)        return the integer descriptor of the argument stream
       fopen(3)         stream open functions
       fprintf(3)       formatted output conversion
       fpurge(3)        flush a stream
       fputc(3)         output a character or word to a stream
       fputs(3)         output a line to a stream
       fread(3)         binary stream input/output
       freopen(3)       stream open functions
       fscanf(3)        input format conversion
       fseek(3)         reposition a stream
       fsetpos(3)       reposition a stream
       ftell(3)         reposition a stream
       fwrite(3)        binary stream input/output
       getc(3)          get next character or word from input stream
       getchar(3)       get next character or word from input stream
       gets(3)          get a line from a stream
       getw(3)          get next character or word from input stream
       mktemp(3)        make temporary filename (unique)
       perror(3)        system error messages
       printf(3)        formatted output conversion
       putc(3)          output a character or word to a stream
       putchar(3)       output a character or word to a stream
       puts(3)          output a line to a stream
       putw(3)          output a character or word to a stream
       remove(3)        remove directory entry
       rewind(3)        reposition a stream
       scanf(3)         input format conversion
       setbuf(3)        stream buffering operations
       setbuffer(3)     stream buffering operations
       setlinebuf(3)    stream buffering operations
       setvbuf(3)       stream buffering operations
       sprintf(3)       formatted output conversion
       sscanf(3)        input format conversion
       strerror(3)      system error messages
       sys_errlist(3)   system error messages
       sys_nerr(3)      system error messages
       tempnam(3)       temporary file routines
       tmpfile(3)       temporary file routines
       tmpnam(3)        temporary file routines
       ungetc(3)        un-get character from input stream
       vfprintf(3)      formatted output conversion
       vfscanf(3)       input format conversion
       vprintf(3)       formatted output conversion
       vscanf(3)        input format conversion
       vsprintf(3)      formatted output conversion
       vsscanf(3)       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 5.01 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/.

                                            2017-11-26                                   STDIO(3)