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SCANF(3)                 BSD Library Functions Manual                 SCANF(3)

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

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <stdio.h>

     int
     fscanf(FILE *restrict stream, const char *restrict format, ...);

     int
     scanf(const char *restrict format, ...);

     int
     sscanf(const char *restrict s, const char *restrict format, ...);

     #include <stdarg.h>
     #include <stdio.h>

     int
     vfscanf(FILE *restrict stream, const char *restrict format, va_list arg);

     int
     vscanf(const char *restrict format, va_list arg);

     int
     vsscanf(const char *restrict s, const char *restrict format, va_list arg);

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 s.

     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 the * conversion 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).

     Extended locale versions of these functions are documented in scanf_l(3).  See xlocale(3) for more
     information.

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

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

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

     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 (ell)  Indicates that the conversion will be one of dioux or n and the next pointer is a pointer to a
              long int (rather than int), that the conversion will be one of a, e, f, or g and the next
              pointer is a pointer to double (rather than float), or that the conversion will be one of c, s
              or [ and the next pointer is a pointer to an array of wchar_t (rather than char).

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

     L        Indicates that the conversion will be one of a, e, f, or g and the next pointer is a pointer
              to long double.

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

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

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

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

     In addition to these flags, there may be an optional maximum field width, expressed as a decimal inte-ger, integer,
     ger, 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 bytes are scanned in processing the conversion.  In
     the case of the lc, ls and l[ conversions, the field width specifies the maximum number of multibyte
     characters that will be scanned.  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 `%' charac-ter. character.
           ter.  No conversion is done, and assignment does not occur.

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

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

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

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

     a, A, e, E, f, F, g, G
           Matches a floating-point number in the style of strtod(3).  The next pointer must be a pointer to
           float (unless l or L is specified.)

     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.

           If an l qualifier is present, the next pointer must be a pointer to wchar_t, into which the input
           will be placed after conversion by mbrtowc(3).

     S     The same as ls.

     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.

           If an l qualifier is present, the next pointer must be a pointer to wchar_t, into which the input
           will be placed after conversion by mbrtowc(3).

     C     The same as lc.

     [     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.

           If an l qualifier is present, the next pointer must be a pointer to wchar_t, into which the input
           will be placed after conversion by mbrtowc(3).

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

     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 decimal point character is defined in the program's locale (category LC_NUMERIC).

     For backwards compatibility, a ``conversion'' of `%\0' causes an immediate return of EOF.

RETURN VALUES
     These functions return the number of input items assigned.  This can be fewer than provided for, or
     even zero, in the event of a matching failure.  Zero indicates that, although there was input avail-able, available,
     able, 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 conversion such as an end-of-file occurs.  If an error or end-of-file occurs after conver-sion conversion
     sion has begun, the number of conversions which were successfully completed is returned.

SEE ALSO
     getc(3), mbrtowc(3), printf(3), scanf_l(3), strtod(3), strtol(3), strtoul(3), wscanf(3)

STANDARDS
     The functions fscanf(), scanf(), sscanf(), vfscanf(), vscanf(), and vsscanf() conform to ISO/IEC
     9899:1999 (``ISO C99'').

BUGS
     Earlier implementations of fscanf treated %D, %E, %F, %O and %X as their lowercase equivalents with an
     l modifier.  In addition, fscanf treated an unknown conversion character as %d or %D, depending on its
     case.  This functionality has been removed.

     Numerical strings are truncated to 512 characters; for example, %f and %d are implicitly %512f and
     %512d.

     The %n$ modifiers for positional arguments are not implemented.

     The fscanf family of functions do not correctly handle multibyte characters in the format argument.

BSD                             January 4, 2003                            BSD

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