Ubuntu Manpages

<ctype.h>: Character Operations

This realization permits all possible values of integer argument. The toascii() function clears all highest bits. The tolower() and toupper() functions return an input argument as is, if it is not an unsigned char value.
int toascii (int __c)
int tolower (int __c)
int toupper (int __c)

These functions perform various operations on characters.

#include <ctype.h>

Checks for an alphanumeric character. It is equivalent to (isalpha(c) || isdigit(c)).

Checks for an alphabetic character. It is equivalent to (isupper(c) || islower(c)).

Checks whether c is a 7-bit unsigned char value that fits into the ASCII character set.

Checks for a blank character, that is, a space or a tab.

Checks for a control character.

Checks for a digit (0 through 9).

Checks for any printable character except space.

Checks for a lower-case character.

Checks for any printable character including space.

Checks for any printable character which is not a space or an alphanumeric character.

Checks for white-space characters. For the avr-libc library, these are: space, form-feed ('\f'), newline ('\n'), carriage return ('\r'), horizontal tab ('\t'), and vertical tab ('\v').

Checks for an uppercase letter.

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.

Converts c to a 7-bit unsigned char value that fits into the ASCII character set, by clearing the high-order bits.

Warning:

Many people will be unhappy if you use this function. This function will convert accented letters into random characters.

Converts the letter c to lower case, if possible.

Converts the letter c to upper case, if possible.

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