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

 

NAME

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

LIBRARY

      Standard C Library (libc, -lc)
 

SYNOPSIS

      #include <stdio.h>
 
      int
      scanf(const char * restrict format, ...);
 
      int
      fscanf(FILE * restrict stream, const char * restrict format, ...);
 
      int
      sscanf(const char * restrict str, const char * restrict format, ...);
 
      #include <stdarg.h>
 
      int
      vscanf(const char * restrict format, va_list ap);
 
      int
      vsscanf(const char * restrict str, const char * restrict format,
              va_list ap);
 
      int
      vfscanf(FILE * restrict stream, const char * restrict 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 respec‐
      tively.  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).
 

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.
 
      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 conver‐
               sion 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 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 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 ‘%’ 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.
 
      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 oth‐
            erwise.  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 speci‐
            fied.)
 
      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 ] charac‐
            ter.  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 cir‐
            cumflex, 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.
 
      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.
      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 fail‐
      ure.  Zero indicates that, while there was input available, no conver‐
      sions 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 conversion has
      begun, the number of conversions which were successfully completed is
      returned.
      getc(3), mbrtowc(3), printf(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 scanf treated %D, %E, %F, %O and %X as their
      lowercase equivalents with an l modifier.  In addition, scanf 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 scanf family of functions do not correctly handle multibyte charac‐
      ters in the format argument.
 

Sections

Based on BSD UNIX
FreeBSD is an advanced operating system for x86 compatible (including Pentium and Athlon), amd64 compatible (including Opteron, Athlon64, and EM64T), UltraSPARC, IA-64, PC-98 and ARM architectures. It is derived from BSD, the version of UNIX developed at the University of California, Berkeley. It is developed and maintained by a large team of individuals. Additional platforms are in various stages of development.