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NAME

       stdio - standard input/output library functions

LIBRARY

       Standard C library (libc, -lc)

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
       fmemopen(3)          open memory as stream
       fopen(3)             stream open functions
       fopencookie(3)       open a custom stream
       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)
       open_memstream(3)    open a dynamic memory buffer stream
       open_wmemstream(3)   open a dynamic memory buffer stream
       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

STANDARDS

       C11, POSIX.1-2008.

HISTORY

       C89, POSIX.1-2001.

SEE ALSO

       close(2), open(2), read(2), write(2), stdout(3), unlocked_stdio(3)