Manual Pages  — CTYPE

digittoint, isalnum, isalpha, isascii, isblank, iscntrl, isdigit, isgraph, ishexnumber, isideogram, islower, isnumber, isphonogram, isprint, ispunct, isrune, isspace, isspecial, isupper, isxdigit, toascii, tolower, toupper – character classification functions

LIBRARY SYNOPSIS DESCRIPTION SEE ALSO STANDARDS HISTORY

Standard C Library (libc, -lc)

#include <ctype.h>

int
digittoint(int c);

int
isalnum(int c);

int
isalpha(int c);

int
isascii(int c);

int
iscntrl(int c);

int
isdigit(int c);

int
isgraph(int c);

int
ishexnumber(int c);

int
isideogram(int c);

int
islower(int c);

int
isnumber(int c);

int
isphonogram(int c);

int
isspecial(int c);

int
isprint(int c);

int
ispunct(int c);

int
isrune(int c);

int
isspace(int c);

int
isupper(int c);

int
isxdigit(int c);

int
toascii(int c);

int
tolower(int c);

int
toupper(int c);

The above functions perform character tests and conversions on the integer c. They are available as macros, defined in the include file <ctype.h>, or as true functions in the C library. See the specific manual pages for more information.

These functions, except for digittoint(), isascii(), ishexnumber(), isideogram(), isnumber(), isphonogram(), isrune(), isspecial() and toascii(), conform to ISO/IEC 9899:1990 ("ISO C90").

The functions isalpha(), isupper(), islower(), isdigit(), isalnum(), isspace(), ispunct(), isprint(), iscntrl(), and isascii() first appeared in AT&T v7 .