C Programming/ctype.h/Function reference
isalnum edit
Prototype edit
int isalnum(int c);
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This function tests whether the character c is of class alpha or digit in the current locale.
isalpha edit
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int isalpha(int c);
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This function tests whether the character c is alphabetic in the current locale.
isblank edit
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int isblank(int c);
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This function tests whether the character c is a space or a tab in the current locale.
iscntrl edit
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int iscntrl(int c);
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This function returns true if c is a control character (that is, a character that is not a printing character).
isdigit edit
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int isdigit(int c);
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This function returns true if c is a decimal digit ('0' through '9').
isgraph edit
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int isgraph(int c);
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This function returns true if c is a character that has a glyph associated with it. Whitespace characters are not considered graphic.
islower edit
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int islower(int c);
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This function tests whether the character c is lowercase.
isprint edit
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int isprint(int c);
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This function returns true if c is a printing character. Printing characters include all the graphic characters, plus the space character.
ispunct edit
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int isalnum(int c);
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This function returns true if c is a punctuation character. This includes any printing character that is not alphanumeric or a space character.
isspace edit
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int isspace(int c);
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Returns true if c is a whitespace character. In the standard C locale, these are the valid space characters:
- Spaces
- Horizontal tabs
- Vertical tabs
- Newlines
- Formfeeds
- Carriage returns
isupper edit
Prototype edit
int isupper(int c);
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This function tests whether the character c is uppercase.
isxdigit edit
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int isxdigit(int c);
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This function tests whether the character c is a hexadecimal dight ('0' through 'F').
tolower edit
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int tolower(int c);
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This function transliterates an uppercase character to lowercase and returns it. If c is not an uppercase letter, c is returned unchanged.
toupper edit
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int toupper(int c);
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This function transliterates a lowercase character to uppercase and returns it. If c is not a lowercase letter, c is returned unchanged.