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is, isw Routines

Visual Studio 6.0
isalnum, iswalnum islower, iswlower
isalpha, iswalpha isprint, iswprint
__isascii, iswascii ispunct, iswpunct
iscntrl, iswcntrl isspace, iswspace
__iscsym, __iscsymf isupper, iswupper
isdigit, iswdigit isxdigit, iswxdigit
isgraph, iswgraph iswctype

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.

For each of the is routines, the result of the test for the specified condition depends on the LC_CTYPE category setting of the current locale; see setlocale for more information. 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 true. iswalpha returns true only for wide characters for which iswupper or iswlower is true.

iswascii

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

iswcntrl

Control wide 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 true. iswlower returns true 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 true.

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 true. iswupper returns true only for wide characters that correspond to uppercase characters.

iswxdigit

Wide character that corresponds to a hexadecimal-digit character.

Example

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

 * Editor's note: the following output is significantly
 * shortened with the use of ellipses. This full output
 * is too long and repetitive.
 */

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

void main( void )
{
   int ch;
   for( ch = 0; ch <= 0x7F; ch++ )
   {
      printf( "%.2x  ", ch );
      printf( " %c", isprint( ch )  ? ch   : '\0' );
      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  
01  
02  
03  
04  
05  
06  
07  
08  
09  
0a  
0b  
0c  
0d  
0e  
0f  
10  
11  
12  
13  
14  
15  
16  
17  
18  
19  
1a  
1b  
1c  
1d  
1e  
1f  
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  

Character Classification RoutinesLocale Routines

See Also   setlocale, to Function Overview

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