is, isw Routines

isalnum, iswalnum, _isalnum_l, _iswalnum_l

islower, iswlower, _islower_l, _iswlower_l

isalpha, iswalpha, _isalpha_l, _iswalpha_l

isprint, iswprint, _isprint_l, _iswprint_l

__isascii, iswascii

ispunct, iswpunct, _ispunct_l, _iswpunct_l

iscntrl, iswcntrl, _iscntrl_l, _iswcntrl_l

isspace, iswspace, _isspace_l, _iswspace_l

__iscsym, __iswcsym __iscsymf, __iswcsymf

isupper, _isupper_l, iswupper, _iswupper_l

isdigit, iswdigit, _isdigit_l, _iswdigit_l

_isctype, iswctype, _isctype_l, _iswctype_l

isgraph, iswgraph, _isgraph_l, _iswgraph_l

isxdigit, iswxdigit, _isxdigit_l, _iswxdigit_l

isleadbyte, _isleadbyte_l

Remarks

These routines test characters for specified conditions.

The is routines produce meaningful results for any integer argument from –1 (EOF) to UCHAR_MAX (0xFF), inclusive. The expected argument type is int.

Warning

For the is routines, passing an argument of type char may yield unpredictable results. An SBCS or MBCS single-byte character of type char with a value greater than 0x7F is negative. If a char is passed, the compiler may convert the value to a signed int or a signed long. This value may be sign-extended by the compiler, with unexpected results.

The isw routines produce meaningful results for any integer value from – 1 (WEOF) to 0xFFFF, inclusive. The wint_t data type is defined in WCHAR.H as an unsigned short; it can hold any wide character or the wide-character end-of-file (WEOF) value.

The output value is affected by the setting of the LC_CTYPE category setting of the locale; see setlocale for more information. The versions of these functions without the _l suffix use the current locale for this locale-dependent behavior; the versions with the _l suffix are identical except that they use the locale parameter passed in instead.

In the "C" locale, the test conditions for the is routines are as follows:

  • isalnum
    Alphanumeric (A – Z, a – z, or 0 – 9).

  • isalpha
    Alphabetic (A – Z or a – z).

  • __isascii
    ASCII character (0x00 – 0x7F).

  • iscntrl
    Control character (0x00 – 0x1F or 0x7F).

  • __iscsym
    Letter, underscore, or digit.

  • __iscsymf
    Letter or underscore.

  • isdigit
    Decimal digit (0 – 9).

  • isgraph
    Printable character except space ( ).

  • islower
    Lowercase letter (a – z).

  • isprint
    Printable character including space (0x20 – 0x7E).

  • ispunct
    Punctuation character.

  • isspace
    White-space character (0x09 – 0x0D or 0x20).

  • isupper
    Uppercase letter (A – Z).

  • isxdigit
    Hexadecimal digit (A – F, a – f, or 0 – 9).

For the isw routines, the result of the test for the specified condition is independent of locale. The test conditions for the isw functions are as follows:

  • iswalnum
    iswalpha or iswdigit.

  • iswalpha
    Any wide character that is one of an implementation-defined set for which none of iswcntrl, iswdigit, iswpunct, or iswspace is nonzero. iswalpha returns nonzero only for wide characters for which iswupper or iswlower is nonzero.

  • iswascii
    Wide-character representation of ASCII character (0x0000 – 0x007F).

  • iswcntrl
    Control wide character.

  • __iswcsym
    Any wide character for which isalnum is true, or the '_' character.

  • __iswcsymf
    Any wide character for which iswalpha is true, or the '_' character.

  • iswctype
    Character has property specified by the desc argument. For each valid value of the desc argument of iswctype, there is an equivalent wide-character classification routine, as shown in the following table:

    Equivalence of iswctype( c, desc ) to Other isw Testing Routines

    Value of desc argument

    iswctype( c, desc ) equivalent

    _ALPHA

    iswalpha( c )

    _ALPHA | _DIGIT

    iswalnum( c )

    _CONTROL

    iswcntrl( c )

    _DIGIT

    iswdigit( c )

    _ALPHA | _DIGIT | _PUNCT

    iswgraph( c )

    _LOWER

    iswlower( c )

    _ALPHA | _BLANK | _DIGIT | _PUNCT

    iswprint( c )

    _PUNCT

    iswpunct( c )

    _SPACE

    iswspace( c )

    _UPPER

    iswupper( c )

    _HEX

    iswxdigit( c )

  • iswdigit
    Wide character corresponding to a decimal-digit character.

  • iswgraph
    Printable wide character except space wide character (L' ').

  • iswlower
    Lowercase letter, or one of implementation-defined set of wide characters for which none of iswcntrl, iswdigit, iswpunct, or iswspace is nonzero. iswlower returns nonzero only for wide characters that correspond to lowercase letters.

  • iswprint
    Printable wide character, including space wide character (L' ').

  • iswpunct
    Printable wide character that is neither space wide character (L' ') nor wide character for which iswalnum is nonzero.

  • iswspace
    Wide character that corresponds to standard white-space character or is one of implementation-defined set of wide characters for which iswalnum is false. Standard white-space characters are: space (L' '), formfeed (L'\f'), newline (L'\n'), carriage return (L'\r'), horizontal tab (L'\t'), and vertical tab (L'\v').

  • iswupper
    Wide character that is uppercase or is one of an implementation-defined set of wide characters for which none of iswcntrl, iswdigit, iswpunct, or iswspace is nonzero. iswupper returns nonzero only for wide characters that correspond to uppercase characters.

  • iswxdigit
    Wide character that corresponds to a hexadecimal-digit character.

Example

// crt_isfam.c
/* This program tests all characters between 0x0
 * and 0x7F, then displays each character with abbreviations
 * for the character-type codes that apply.
 */

#include <stdio.h>
#include <ctype.h>

int main( void )
{
   int ch;
   for( ch = 0; ch <= 0x7F; ch++ )
   {
      printf( "%.2x  ", ch );
      printf( " %c", isprint( ch )  ? ch   : ' ' );
      printf( "%4s", isalnum( ch )  ? "AN" : "" );
      printf( "%3s", isalpha( ch )  ? "A"  : "" );
      printf( "%3s", __isascii( ch )  ? "AS" : "" );
      printf( "%3s", iscntrl( ch )  ? "C"  : "" );
      printf( "%3s", __iscsym( ch )  ? "CS "  : "" );
      printf( "%3s", __iscsymf( ch )  ? "CSF"  : "" );
      printf( "%3s", isdigit( ch )  ? "D"  : "" );
      printf( "%3s", isgraph( ch )  ? "G"  : "" );
      printf( "%3s", islower( ch )  ? "L"  : "" );
      printf( "%3s", ispunct( ch )  ? "PU" : "" );
      printf( "%3s", isspace( ch )  ? "S"  : "" );
      printf( "%3s", isprint( ch )  ? "PR" : "" );
      printf( "%3s", isupper( ch )  ? "U"  : "" );
      printf( "%3s", isxdigit( ch ) ? "X"  : "" );
      printf( ".\n" );
   }
}

Output

00            AS  C                              .
01            AS  C                              .
02            AS  C                              .
03            AS  C                              .
04            AS  C                              .
05            AS  C                              .
06            AS  C                              .
07            AS  C                              .
08            AS  C                              .
09            AS  C                    S         .
0a            AS  C                    S         .
0b            AS  C                    S         .
0c            AS  C                    S         .
0d            AS  C                    S         .
0e            AS  C                              .
0f            AS  C                              .
10            AS  C                              .
11            AS  C                              .
12            AS  C                              .
13            AS  C                              .
14            AS  C                              .
15            AS  C                              .
16            AS  C                              .
17            AS  C                              .
18            AS  C                              .
19            AS  C                              .
1a            AS  C                              .
1b            AS  C                              .
1c            AS  C                              .
1d            AS  C                              .
1e            AS  C                              .
1f            AS  C                              .
20            AS                       S PR      .
21   !        AS              G    PU    PR      .
22   "        AS              G    PU    PR      .
23   #        AS              G    PU    PR      .
24   $        AS              G    PU    PR      .
25   %        AS              G    PU    PR      .
26   &        AS              G    PU    PR      .
27   '        AS              G    PU    PR      .
28   (        AS              G    PU    PR      .
29   )        AS              G    PU    PR      .
2a   *        AS              G    PU    PR      .
2b   +        AS              G    PU    PR      .
2c   ,        AS              G    PU    PR      .
2d   -        AS              G    PU    PR      .
2e   .        AS              G    PU    PR      .
2f   /        AS              G    PU    PR      .
30   0  AN    AS   CS      D  G          PR     X.
31   1  AN    AS   CS      D  G          PR     X.
32   2  AN    AS   CS      D  G          PR     X.
33   3  AN    AS   CS      D  G          PR     X.
34   4  AN    AS   CS      D  G          PR     X.
35   5  AN    AS   CS      D  G          PR     X.
36   6  AN    AS   CS      D  G          PR     X.
37   7  AN    AS   CS      D  G          PR     X.
38   8  AN    AS   CS      D  G          PR     X.
39   9  AN    AS   CS      D  G          PR     X.
3a   :        AS              G    PU    PR      .
3b   ;        AS              G    PU    PR      .
3c   <        AS              G    PU    PR      .
3d   =        AS              G    PU    PR      .
3e   >        AS              G    PU    PR      .
3f   ?        AS              G    PU    PR      .
40   @        AS              G    PU    PR      .
41   A  AN  A AS   CS CSF     G          PR  U  X.
42   B  AN  A AS   CS CSF     G          PR  U  X.
43   C  AN  A AS   CS CSF     G          PR  U  X.
44   D  AN  A AS   CS CSF     G          PR  U  X.
45   E  AN  A AS   CS CSF     G          PR  U  X.
46   F  AN  A AS   CS CSF     G          PR  U  X.
47   G  AN  A AS   CS CSF     G          PR  U   .
48   H  AN  A AS   CS CSF     G          PR  U   .
49   I  AN  A AS   CS CSF     G          PR  U   .
4a   J  AN  A AS   CS CSF     G          PR  U   .
4b   K  AN  A AS   CS CSF     G          PR  U   .
4c   L  AN  A AS   CS CSF     G          PR  U   .
4d   M  AN  A AS   CS CSF     G          PR  U   .
4e   N  AN  A AS   CS CSF     G          PR  U   .
4f   O  AN  A AS   CS CSF     G          PR  U   .
50   P  AN  A AS   CS CSF     G          PR  U   .
51   Q  AN  A AS   CS CSF     G          PR  U   .
52   R  AN  A AS   CS CSF     G          PR  U   .
53   S  AN  A AS   CS CSF     G          PR  U   .
54   T  AN  A AS   CS CSF     G          PR  U   .
55   U  AN  A AS   CS CSF     G          PR  U   .
56   V  AN  A AS   CS CSF     G          PR  U   .
57   W  AN  A AS   CS CSF     G          PR  U   .
58   X  AN  A AS   CS CSF     G          PR  U   .
59   Y  AN  A AS   CS CSF     G          PR  U   .
5a   Z  AN  A AS   CS CSF     G          PR  U   .
5b   [        AS              G    PU    PR      .
5c   \        AS              G    PU    PR      .
5d   ]        AS              G    PU    PR      .
5e   ^        AS              G    PU    PR      .
5f   _        AS   CS CSF     G    PU    PR      .
60   `        AS              G    PU    PR      .
61   a  AN  A AS   CS CSF     G  L       PR     X.
62   b  AN  A AS   CS CSF     G  L       PR     X.
63   c  AN  A AS   CS CSF     G  L       PR     X.
64   d  AN  A AS   CS CSF     G  L       PR     X.
65   e  AN  A AS   CS CSF     G  L       PR     X.
66   f  AN  A AS   CS CSF     G  L       PR     X.
67   g  AN  A AS   CS CSF     G  L       PR      .
68   h  AN  A AS   CS CSF     G  L       PR      .
69   i  AN  A AS   CS CSF     G  L       PR      .
6a   j  AN  A AS   CS CSF     G  L       PR      .
6b   k  AN  A AS   CS CSF     G  L       PR      .
6c   l  AN  A AS   CS CSF     G  L       PR      .
6d   m  AN  A AS   CS CSF     G  L       PR      .
6e   n  AN  A AS   CS CSF     G  L       PR      .
6f   o  AN  A AS   CS CSF     G  L       PR      .
70   p  AN  A AS   CS CSF     G  L       PR      .
71   q  AN  A AS   CS CSF     G  L       PR      .
72   r  AN  A AS   CS CSF     G  L       PR      .
73   s  AN  A AS   CS CSF     G  L       PR      .
74   t  AN  A AS   CS CSF     G  L       PR      .
75   u  AN  A AS   CS CSF     G  L       PR      .
76   v  AN  A AS   CS CSF     G  L       PR      .
77   w  AN  A AS   CS CSF     G  L       PR      .
78   x  AN  A AS   CS CSF     G  L       PR      .
79   y  AN  A AS   CS CSF     G  L       PR      .
7a   z  AN  A AS   CS CSF     G  L       PR      .
7b   {        AS              G    PU    PR      .
7c   |        AS              G    PU    PR      .
7d   }        AS              G    PU    PR      .
7e   ~        AS              G    PU    PR      .
7f            AS  C                              .

See Also

Reference

Character Classification

Locale

setlocale, _wsetlocale

Interpretation of Multibyte-Character Sequences

to Functions