Removing Spaces from a String in C?

Question

What is the easiest and most efficient way to remove spaces from a string in C?

Thanks.

Answer 1

Easiest and most efficient don't usually go together...

Here's a possible solution (untested):

void RemoveSpaces(char* source)
{
  char* i = source;
  char* j = source;
  while(*j != 0)
  {
    *i = *j++;
    if(*i != ' ')
      i++;
  }
  *i = 0;
}

Answer 2

#include <ctype>

char * remove_spaces(char * source, char * target)
{
     while(*source++ && *target)
     {
        if (!isspace(*source)) 
             *target++ = *source;
     }
     return target;
}

Notes;

• This doesn't handle Unicode.

Answer 3

I assume the C string is in a fixed memory, so if you replace spaces you have to shift all characters.

The easiest seems to be to create new string and iterate over the original one and copy only non space characters.

Answer 4

In C, you can replace some strings in-place, for example a string returned by strdup():

char *str = strdup(" a b c ");

char *write = str, *read = str;
do {
   if (*read != ' ')
       *write++ = *read;
} while (*read++);

printf("%s\n", str);

Other strings are read-only, for example those declared in-code. You'd have to copy those to a newly allocated area of memory and fill the copy by skipping the spaces:

char *oldstr = " a b c ";

char *newstr = (char*) malloc(strlen(oldstr)+1);
char *np = newstr, *op = oldstr;
do {
   if (*op != ' ')
       *np++ = *op;
} while (*op++);

printf("%s\n", newstr);

You can see why people invented other languages ;)

Answer 5

Braces are unnecessary:

do while(isspace(*s)) s++; while(*d++ = *s++);

The above should be perfectly safe.

But, if you can risk some undefined behavior, and never have empty strings, you can get rid of the body:

while(*(d+=!isspace(*s++)) = *s);

Heck, if by space you mean just space character, so much "bloat" can be removed:

while(*(d+=*s++!=' ')=*s);

Don't use that in production :)