What is the symbol for whitespace in C?

问题

I am trying to figure out how to check if a character is equal to white-space in C. I know that tabs are '\t' and newlines are '\n', but I want to be able to check for just a regular normal space (from the space-bar) inside of an if statement.

Does anybody know what is the character for this?

回答1:

There is no particular symbol for whitespace. It is actually a set of some characters which are customarily:

' '      space 
'\t'     horizontal tab 
'\n'     newline
'\v'     vertical tab 
'\f'     feed 
'\r'     carriage return

Use isspace standard library function from ctype.h if you want to check for any of these white-spaces.

For just a space, use ' '.

回答2:

The character representation of a Space is simply ' '.

void foo (const char *s)
{
    unsigned char c;
    ...
    if (c == ' ')
        ...
}

But if you are really looking for all whitespace, then C has a function (actually it's often a macro) for that:

#include <ctype.h>
...

void foo (const char *s)
{
    char c;
    ...
    if (isspace(c))
        ...
}

You can read about isspace here

If you really want to catch all non-printing characters, the function to use is isprint from the same library. This deals with all of the characters below 0x20 (the ASCII code for a space) and above 0x7E (0x7f is the code for DEL, and everything above that is an extension).

In raw code this is equivalent to:

if (c < ' ' || c >= 0x7f)
    // Deal with non-printing characters.

回答3:

The ASCII value of Space is 32. So you can compare your char to the octal value of 32 which is 40 or its hexadecimal value which is 20.

if(c == '\40') { ... }

if(c == '\x20') { ... }

Any number after the \ is assumed to be octal, if the character just after \ is not x, in which case it is considered to be a hexadecimal.

回答4:

No special escape sequence is required: you can just type the space directly:

if (char_i_want_to_test == ' ') { 
    // Do something because it is space
}

In ASCII, space is code 32, so you could specify space by '\x20' or even 32, but you really shouldn't do that.

Aside: the word "whitespace" is a catch all for space, tab, newline, and all of that. When you're referring specifically to the ordinary space character, you shouldn't use the term.

回答5:

make use of isspace function .

The C library function int isspace(int c) checks whether the passed character is white-space.

sample code:

    int main()
    {

       char var= ' ';

       if( isspace(var) )
       {
          printf("var1 = |%c| is a white-space character\n", var );
       }
/*instead you can easily compare character with ' '  
  */     
    }

Standard white-space characters are −

' '   (0x20)    space (SPC)
'\t'    (0x09)  horizontal tab (TAB)
'\n'    (0x0a)  newline (LF)
'\v'    (0x0b)  vertical tab (VT)
'\f'    (0x0c)  feed (FF)
'\r'    (0x0d)  carriage return (CR)

source : tutorialpoint

回答6:

To check a space symbol you can use the following approach

if ( c == ' ' ) { /*...*/ }

To check a space and/or a tab symbol (standard blank characters) you can use the following approach

#include <ctype.h>

//...

if ( isblank( c ) ) { /*...*/ }

To check a white space you can use the following approach

#include <ctype.h>

//...

if ( isspace( c ) ) { /*...*/ }

回答7:

#include <stdio.h>
main()
{
int c,sp,tb,nl;
sp = 0;
tb = 0;
nl = 0;
while((c = getchar()) != EOF)
{
   switch( c )
{
   case ' ':
        ++sp;
     printf("space:%d\n", sp);
     break;
   case  '\t':
        ++tb;
     printf("tab:%d\n", tb);
     break;
   case '\n':
        ++nl;
     printf("new line:%d\n", nl);
     break;
  }
 }
}

来源：https://stackoverflow.com/questions/30033582/what-is-the-symbol-for-whitespace-in-c

标签

whitespace

space