SCANF(3)						     Linux Programmer's Manual							  SCANF(3)

NAME

       scanf, fscanf, sscanf, vscanf, vsscanf, vfscanf - input format conversion

SYNOPSIS

       #include <stdio.h>
       int scanf(const char *format, ...);
       int fscanf(FILE *stream, const char *format, ...);
       int sscanf(const char *str, const char *format, ...);

       #include <stdarg.h>
       int vscanf(const char *format, va_list ap);
       int vsscanf(const char *str, const char *format, va_list ap);
       int vfscanf(FILE *stream, const char *format, va_list ap);

DESCRIPTION

       The  scanf  family  of  functions scans input according to a format as described below.	This format may contain conversion specifiers; the
       results from such conversions, if any, are stored through the pointer arguments.  The scanf function reads input from  the  standard  input
       stream stdin, fscanf reads input from the stream pointer stream, and sscanf reads its input from the character string pointed to by str.

       The  vfscanf function is analogous to vfprintf(3) and reads input from the stream pointer stream using a variable argument list of pointers
       (see stdarg(3).	The vscanf function scans a variable argument list from the standard input and	the  vsscanf  function	scans  it  from  a
       string; these are analogous to the vprintf and vsprintf functions respectively.

       Each  successive  pointer  argument  must correspond properly with each successive conversion specifier (but see `suppression' below).  All
       conversions are introduced by the % (percent sign) character.  The format string may also contain other characters.  White space  (such	as
       blanks,	tabs,  or  newlines)  in the format string match any amount of white space, including none, in the input.  Everything else matches
       only itself.  Scanning stops when an input character does not match such a format character.  Scanning also stops when an input	conversion
       cannot be made (see below).

CONVERSIONS

       Following the % character introducing a conversion there may be a number of flag characters, as follows:

       *      Suppresses  assignment.  The conversion that follows occurs as usual, but no pointer is used; the result of the conversion is simply
	      discarded.

       a      Indicates that the conversion will be s, the needed memory space for the string will be malloc'ed  and the pointer  to  it  will	be
	      assigned to the char pointer variable, which does not have to be initialized before.  This flag does not exist in ANSI C.

       h      Indicates that the conversion will be one of dioux or n and the next pointer is a pointer to a short int (rather than int).

       l      Indicates either that the conversion will be one of dioux or n and the next pointer is a pointer to a long int (rather than int), or
	      that the conversion will be one of efg and the next pointer is a pointer to double (rather than float).  Specifying two l  flags	is
	      equivalent to the L flag.

       L      Indicates  that  the  conversion will be either efg and the next pointer is a pointer to long double or the conversion will be dioux
	      and the next pointer is a pointer to long long.  (Note that long long is not an ANSI C type. Any program using this will not be por-
	      table to all architectures).

       q      equivalent to L.	This flag does not exist in ANSI C.

       In addition to these flags, there may be an optional maximum field width, expressed as a decimal integer, between the % and the conversion.
       If no width is given, a default of `infinity' is used (with one exception, below); otherwise at most this many characters  are  scanned	in
       processing  the conversion.  Before conversion begins, most conversions skip white space; this white space is not counted against the field
       width.

       The following conversions are available:

       %      Matches a literal `%'.  That is, `%%' in the format string matches a single input `%' character.	No conversion is done, and assign-
	      ment does not occur.

       d      Matches an optionally signed decimal integer; the next pointer must be a pointer to int.

       D      Equivalent  to  ld;  this exists only for backwards compatibility.  (Note: thus only in libc4. In libc5 and glibc the %D is silently
	      ignored, causing old programs to fail mysteriously.)

       i      Matches an optionally signed integer; the next pointer must be a pointer to int.	The integer is read in base 16 if it  begins  with
	      `0x' or `0X', in base 8 if it begins with `0', and in base 10 otherwise.	Only characters that correspond to the base are used.

       o      Matches an unsigned octal integer; the next pointer must be a pointer to unsigned int.

       u      Matches an unsigned decimal integer; the next pointer must be a pointer to unsigned int.

       x      Matches an unsigned hexadecimal integer; the next pointer must be a pointer to unsigned int.

       X      Equivalent to x

       f      Matches an optionally signed floating-point number; the next pointer must be a pointer to float.

       e      Equivalent to f.

       g      Equivalent to f.

       E      Equivalent to f

       s      Matches  a sequence of non-white-space characters; the next pointer must be a pointer to char, and the array must be large enough to
	      accept all the sequence and the terminating NUL character.  The input string stops at white space or at  the  maximum  field  width,
	      whichever occurs first.

       c      Matches  a sequence of width count characters (default 1); the next pointer must be a pointer to char, and there must be enough room
	      for all the characters (no terminating NUL is added).  The usual skip of leading white space is suppressed.   To	skip  white  space
	      first, use an explicit space in the format.

       [      Matches a nonempty sequence of characters from the specified set of accepted characters; the next pointer must be a pointer to char,
	      and there must be enough room for all the characters in the string, plus a terminating NUL character.  The  usual  skip  of  leading
	      white  space  is	suppressed.   The string is to be made up of characters in (or not in) a particular set; the set is defined by the
	      characters between the open bracket [ character and a close bracket ] character.	The set excludes those	characters  if	the  first
	      character  after	the  open bracket is a circumflex ^.  To include a close bracket in the set, make it the first character after the
	      open bracket or the circumflex; any other position will end the set.  The hyphen character - is also special;  when  placed  between
	      two  other  characters,  it  adds all intervening characters to the set.	To include a hyphen, make it the last character before the
	      final close bracket.  For instance, `[^]0-9-]' means the set `everything except close bracket, zero through nine, and hyphen'.   The
	      string ends with the appearance of a character not in the (or, with a circumflex, in) set or when the field width runs out.

       p      Matches a pointer value (as printed by `%p' in printf(3); the next pointer must be a pointer to void.

       n      Nothing  is  expected;  instead, the number of characters consumed thus far from the input is stored through the next pointer, which
	      must be a pointer to int.  This is not a conversion, although it can be suppressed with the * flag.  The C standard says: `Execution
	      of a %n directive does not increment the assignment count returned at the completion of execution' but the Corrigendum seems to con-
	      tradict this. Probably it is wise not to make any assumptions on the effect of %n conversions on the return value.

RETURN VALUE

       These functions return the number of input items assigned, which can be fewer than provided for, or even zero, in the event of  a  matching
       failure.   Zero	indicates  that,  while there was input available, no conversions were assigned; typically this is due to an invalid input
       character, such as an alphabetic character for a `%d' conversion.  The value EOF is returned if an input failure occurs before any  conver-
       sion such as an end-of-file occurs. If an error or end-of-file occurs after conversion has begun, the number of conversions which were suc-
       cessfully completed is returned.

SEE ALSO

       strtol(3), strtoul(3), strtod(3), getc(3), printf(3)

CONFORMING TO

       The functions fscanf, scanf, and sscanf conform to ANSI X3.159-1989 (``ANSI C'').

       The q flag is the BSD 4.4 notation for long long, while ll or the usage of L in integer conversions is the GNU notation.

       The Linux version of these functions is based on the GNU libio library. Take a look at the info documentation of GNU libc (glibc-1.08)  for
       a more concise description.

BUGS

       All  functions  are fully ANSI X3.159-1989 conformant, but provide the additional flags q and a as well as an additional behaviour of the L
       and l flags. The latter may be considered to be a bug, as it changes the behaviour of flags defined in ANSI X3.159-1989.

       Some combinations of flags defined by ANSI C are not making sense in ANSI C (e.g.  %Ld).  While they may have a well-defined  behaviour	on
       Linux,  this  need  not to be so on other architectures. Therefore it usually is better to use flags that are not defined by ANSI C at all,
       i.e. use q instead of L in combination with diouxX conversions or ll.

       The usage of q is not the same as on BSD 4.4, as it may be used in float conversions equivalently to L.

LINUX MANPAGE
							    1995-11-01								  SCANF(3)