[Linux C] character test function

I. Overview

The character test function is included in the header file <ctype. h>

These are macro definitions, not real functions.

1) isalnum test whether the character is an English letter or number

#include <stdio.h>#include <ctype.h>int main(){   char str[]="12#$%sdfsfsf";   int i;   for(i=0;str[i]!=0;++i)if(isalnum(str[i]))printf("%c is an alphanumberic character\n",str[i]);   return 0;}

2) isalpha test for English letters

#include <stdio.h>#include <ctype.h>int main(){   char str[]="12#$%sdfsfsf";   int i;   for(i=0;str[i]!=0;++i)if(isalpha(str[i]))printf("%c is an alpha character\n",str[i]);   return 0;}

3) isascii test whether it is an ASCII character

#include <stdio.h>#include <ctype.h>int main(){   int i;   for(i=125;i<130;++i)if(isascii(i))printf("%d is an ascii character\n",i);        elseprintf("%d is not an ascii character\n",i);   return 0;}

4) The isblank test character is a white space character

5) iscntrl (c) test whether it is an ASCII control code, that is, whether it is between 0 and 31.

6) isdigit test whether it is Arabic numerals

7) isgraph test whether it is a printable character, not a blank character (see 10)

8) islower test whether it is a lowercase English letter

9) isprint test whether the character is printable similar to isgraph

10) isspace test whether the characters are white spaces '', '\ t',' \ n', '\ F', and' \ V'

11) ispunct test whether it is a punctuation or special symbol

12) isupper test whether it is a capital English letter

13) isxdigit test whether the character is a hexadecimal number 0 1 2 2 3 4 5 6 7 8 9 A B C D E F