C library - iswblank() function

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The C wctype library iswblank() function is used to check whether a given wide character (of type wint_t) is classified as a blank character.

The blank includes a white space that separate the words in a sentence by the current C locale. In the default C locale, only space (0x20) and horizontal tab (0x09) are blank characters.

This function is useful for text processing programs, user input validation, word processing and text editor tools, or etc.

Syntax

Following is the C library syntax of iswblank() function −

int iswblank( wint_t ch );

Parameters

This function accepts a single parameter −

• ch − It is a wide character of type 'wint_t' to be checked.

Return Value

This function returns Non-zero value if the wide character is a blank character, zero otherwise.

Example 1

The following is the basic c example that demonstrate the use of iswblank().

#include <locale.h>
#include <stdio.h>
#include <wchar.h>
#include <wctype.h>

int main(void) {
   // Set the locale to "en_US.utf8"
   setlocale(LC_ALL, "en_US.utf8");
   
   wchar_t wchar =  L'\t';   
   if(iswblank(wchar)==1){
       printf("Character '%lc' (%#x) is blank character\n", wchar, wchar);
   }
   else{
       printf("Character '%lc' (%#x) is not a blank character\n", wchar, wchar);
   }

   return 0;
}

Output

Following is the output −

Character '	' (0x9) is blank character

Example 2

Let's create another c program and use iswblank() to validate whether the elements of the array is blank or not.

#include <locale.h>
#include <stdio.h>
#include <wchar.h>
#include <wctype.h>

int main(void) {
   // Set the locale to "en_US.utf8"
   setlocale(LC_ALL, "en_US.utf8");

   // Define an array of wide characters
   wchar_t wchar[] = { L'A', L' ', L'\t', L'@' };
   size_t len = sizeof(wchar) / sizeof(wchar[0]);
   
   printf("Checking blank characters:\n");
   for (size_t i = 0; i < len; ++i) {
      wchar_t ch = wchar[i];
      printf("Character '%lc' (%#x) is %s blank character\n", ch, ch, iswblank(ch) ? "a" : "not a");
   }

   return 0;
}

Output

Following is the output −

Checking blank characters:
Character 'A' (0x41) is not a blank character
Character ' ' (0x20) is a blank character
Character ' ' (0x9) is a blank character
Character '@' (0x40) is not a blank character

Example 3

The below c example uses the iswblank() function to break a statement after encountering blank.

#include <stdio.h>
#include <wchar.h>
#include <wctype.h>

int main(void) {
   // wide char array
   wchar_t wc[] = L"Tutrialspoint India pvt ltd";
   // find the length of wide char
   size_t len = wcslen(wc);

   for (size_t i = 0; i < len; ++i) {
      // Check if the current character is blank
      if (iswblank(wc[i])) {
         // Print a newline character if blanck is found
         putchar('\n');
      } else {
         // Print the current character if it's not blank
         putchar(wc[i]);
      }
   }
   return 0;
}

Output

Following is the output −

Tutrialspoint
India
pvt
ltd