Header File 

ctype.h, wctype.h, mbstring.h 

Category 

Classification Routines 

Prototype 

int isspace(int c); 

int iswspace(wint_t c); 

int _ismbcspace(unsigned int c); 

Description 

Tests for space character. 

isspace is a macro that classifies ASCII-coded integer values by table lookup. The macro is affected by the current locale’s LC_CTYPE category. 

You can make this macro available as a function by undefining (#undef) it. 

Return Value 

isspace returns nonzero if c is a space, tab, carriage return, new line, vertical tab, formfeed (0x09 to 0x0D, 0x20), or any other locale-defined space character. 

Example  

#include <stdio.h>
#include <ctype.h>
int main(void)
{
  char c = 'C';
  if (isspace(c))
    printf("%c is white space\n",c);
  else 
    printf("%c is not white space\n",c);
  return 0;
}

Portability