GNU/Linux man pages
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CentOS 5.1 |
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iscntrl(3) |
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isalnum, isalpha, isascii, isblank, iscntrl, isdigit, isgraph, islower, isprint, ispunct, isspace, isupper, isxdigit − character classification routines
#include <ctype.h>
int
isalnum(int c);
int isalpha(int c);
int isascii(int c);
int isblank(int c);
int iscntrl(int c);
int isdigit(int c);
int isgraph(int c);
int islower(int c);
int isprint(int c);
int ispunct(int c);
int isspace(int c);
int isupper(int c);
int isxdigit(int c);
These functions
check whether c, which must have the value of an
unsigned char or EOF, falls into a certain
character class according to the current locale.
isalnum()
checks for an alphanumeric character; it is equivalent to (isalpha(c) || isdigit(c)).
isalpha()
checks for an alphabetic character; in the standard "C" locale, it is equivalent to (isupper(c) || islower(c)). In some locales, there may be additional characters for which isalpha() is true—letters which are neither upper case nor lower case.
isascii()
checks whether c is a 7-bit unsigned char value that fits into the ASCII character set.
isblank()
checks for a blank character; that is, a space or a tab.
iscntrl()
checks for a control character.
isdigit()
checks for a digit (0 through 9).
isgraph()
checks for any printable character except space.
islower()
checks for a lower-case character.
isprint()
checks for any printable character including space.
ispunct()
checks for any printable character which is not a space or an alphanumeric character.
isspace()
checks for white-space characters. In the "C" and "POSIX" locales, these are: space, form-feed (’\f’), newline (’\n’), carriage return (’\r’), horizontal tab (’\t’), and vertical tab (’\v’).
isupper()
checks for an uppercase letter.
isxdigit()
checks for a hexadecimal
digits, i.e. one of
0 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F.
The values returned are non-zero if the character c falls into the tested class, and a zero value if not.
C99, 4.3BSD. isascii() is a BSD extension and is also an SVr4 extension. isblank() conforms to POSIX.1-2001 and C99 7.4.1.3.
The details of what characters belong into which class depend on the current locale. For example, isupper() will not recognize an A-umlaut (Ä) as an uppercase letter in the default C locale.
iswalnum(3), iswalpha(3), iswblank(3), iswcntrl(3), iswdigit(3), iswgraph(3), iswlower(3), iswprint(3), iswpunct(3), iswspace(3), iswupper(3), iswxdigit(3), setlocale(3), tolower(3), toupper(3), ascii(7), locale(7)
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iscntrl(3) | |