isspace

isspace is a function in the C standard library, defined in ctype.h. It tests whether its argument is a white-space character according to the current C locale. In the typical "C" locale, whitespace characters include the space character (' '), form feed ('\f'), newline ('\n'), carriage return ('\r'), horizontal tab ('\t'), and vertical tab ('\v').

The function has the signature int isspace(int ch). It returns a nonzero value if ch is a whitespace character, and zero otherwise. The argument should be representable as an unsigned char or be the value of EOF; passing a plain char value may lead to undefined behavior on platforms where char is signed unless it is cast to (unsigned char). In many implementations, isspace may be defined as a macro rather than a function.

Locale and portability: The classification of whitespace can vary with the program's locale. For locale-aware checks, C provides isspace_l to test with a specific locale. When using isspace, cast the input as (unsigned char) before passing it, and ensure you do not pass values outside the unsigned char range or EOF.

Use cases and examples: isspace is commonly employed in input parsing, tokenization, and whitespace filtering. Example pattern: if (isspace((unsigned char) ch)) { /* skip or split on whitespace */ }

Other languages: Some languages offer similarly named functions with different semantics. For instance, Python's string methods use Unicode-aware whitespace definitions, which differ from the C isspace behavior.