Function Categories

Character Type Macros and Functions

The character type header files, <ctype.h> and <lctype.h> , define several macros that are useful in the analysis of text data. Most of these macros enable you to determine quickly the type of a character (whether it is alphabetic, numeric, punctuation, and so on). These macros refer to an external array that is indexed by the character itself, so they are generally much faster than functions that check the character against a range or discrete list of values. Note that this array is actually indexed by the character value plus 1, so the standard EOF value (-1) can be tested in a macro without yielding a nonsense result. EOF yields a 0 result for all of the macros because it is not defined as any of the character types. Also, note that the results produced by most of these functions are affected by the current locale's LC_CTYPE category, which may cause a different character type array to be used than the one supplied for the default C locale. See Chapter 10, "Localization," in SAS/C Library Reference, Volume 2 for details on locales.

Another advantage of the character type macros is that they prevent problems when programs are moved between machines that use ASCII versus EBCDIC character sets. Programs using these macros are not dependent on a specific character set.

The following are character type macros and functions:

isalnum alphanumeric character test

isalpha alphabetic character test

isascii ASCII character test

iscntrl control character test

iscsym test for valid C identifier symbol

iscsymf test for valid C identifier initial symbol

isdigit test for numeric character

isebcdic EBCDIC character test

isgraph graphic character test

islower lowercase alphabetic character test

isprint printing character test

ispunct punctuation test

isspace white space test

isupper uppercase alphabetic character test

isxdigit hexadecimal digit test

toebcdic reduce integer to EBCDIC character

tolower translate uppercase character to lowercase

toupper translate lowercase character to uppercase.

Character Type Macros and Functions and Their Return Values lists the macros and functions defined in the character type header files <ctype.h> and <lctype.h> . The library conforms to the ISO/ANSI specification in that the macro arguments are evaluated only once. However, many implementations do not conform to this specification. For maximum portability, beware of the side effects of using expressions such as function calls and increment or decrement operators. You should include <ctype.h> or <lctype.h> if you use any of these macros; otherwise, the compiler generates a reference to a function of the same name.

Character Type Macros and Functions and Their Return Values
Function Return Value

isalnum(c) nonzero if c is alphabetic or digit; 0 if not

isalpha(c) nonzero if c is alphabetic; 0 if not

isascii(c)* nonzero if c is the EBCDIC equivalent of an ASCII character; 0 if not

iscntrl(c) nonzero if c is control character; 0 if not

iscsym(c)* nonzero if valid character for C identifier; 0 if not

iscsymf(c) nonzero if valid first character for C identifier; 0 if not

isdigit(c) * nonzero if c is a digit 0-9; 0 if not

isebcdic(c) * nonzero if a valid EBCDIC character; 0 if not

isgraph(c)
nonzero if c is graphic (excluding the blank character); 0 if not

islower(c) nonzero if c is lowercase; 0 if not

isprint(c) nonzero if c is printable (including blank); 0 if not

ispunct(c) nonzero if c is punctuation; 0 if not

isspace(c) nonzero if c is white space; 0 if not

isupper(c) nonzero if c is uppercase; 0 if not

isxdigit(c) * nonzero if c is a hexadecimal digit (0-9, A-F, a-f); if not

toebcdic(c) * truncates integer to valid EBCDIC character

tolower(c) converts c to lowercase, if uppercase

toupper(c) converts c to uppercase, if lowercase

***Character Type Macros and Functions and Their Return Values***
Function	Return Value
`isalnum(c)`	nonzero if `c` is alphabetic or digit; 0 if not
`isalpha(c)`	nonzero if `c` is alphabetic; 0 if not
`isascii(c)*`	nonzero if `c` is the EBCDIC equivalent of an ASCII character; 0 if not
`iscntrl(c)`	nonzero if `c` is control character; 0 if not
`iscsym(c)*`	nonzero if valid character for C identifier; 0 if not
`iscsymf(c)`	nonzero if valid first character for C identifier; 0 if not
`isdigit(c)` *	nonzero if `c` is a digit 0-9; 0 if not
`isebcdic(c)` *	nonzero if a valid EBCDIC character; 0 if not
isgraph(c)	nonzero if `c` is graphic (excluding the blank character); 0 if not
`islower(c)`	nonzero if `c` is lowercase; 0 if not
`isprint(c)`	nonzero if `c` is printable (including blank); 0 if not
`ispunct(c)`	nonzero if `c` is punctuation; 0 if not
`isspace(c)`	nonzero if `c` is white space; 0 if not
`isupper(c)`	nonzero if `c` is uppercase; 0 if not
`isxdigit(c)` *	nonzero if `c` is a hexadecimal digit (0-9, A-F, a-f); if not
`toebcdic(c)` *	truncates integer to valid EBCDIC character
`tolower(c)`	converts `c` to lowercase, if uppercase
`toupper(c)`	converts `c` to uppercase, if lowercase

In Character Type Macros and Functions and Their Return Values, functions marked with *are not affected by the locale's LC_TYPE category.

Note: The toupper and tolower macros generate the value of c unchanged if it does not qualify for the conversion. [cautionend]

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`isalnum`	alphanumeric character test
`isalpha`	alphabetic character test
`isascii`	ASCII character test
`iscntrl`	control character test
`iscsym`	test for valid C identifier symbol
`iscsymf`	test for valid C identifier initial symbol
`isdigit`	test for numeric character
`isebcdic`	EBCDIC character test
`isgraph`	graphic character test
`islower`	lowercase alphabetic character test
`isprint`	printing character test
`ispunct`	punctuation test
`isspace`	white space test
`isupper`	uppercase alphabetic character test
`isxdigit`	hexadecimal digit test
`toebcdic`	reduce integer to EBCDIC character
`tolower`	translate uppercase character to lowercase
`toupper`	translate lowercase character to uppercase.