Question

While coding very simple program for removing blanks, tabs, newlines I came across something I don’t actually catch on first; even though if condition is true only when tab, space or newline doesn’t exist it’s still executed with the mentioned for some reason.. here is the code

#include <cstdio>
#include <cstring>

#include <stdio.h>
#include <string.h>

#define LGT 100

void rem(char s[])
{
 int i;
 for(i=(strlen(s)-1);i>=0;i--)
  if(s[i]!=' ' || s[i]!='\t' || s[i]!='\n')
   break;
  s[i+1]='\0';

}
int main(void)
{
 char v[LGT]={"sdsfg\t"};

 rem(v);
 printf("%s\n",v);
 getchar();
}

Answer 1

The problem is that

  if(s[i]!=' ' || s[i]!='\t' || s[i]!='\n')

Is always true. If s[i] is a space, then the latter two checks are true. If it’s not a space, them the first check is true.

To fix this, change these ors to ands:

if(s[i]!=' ' && s[i]!='\t' && s[i]!='\n')

Or, even better, use isspace:

 if(isspace(s[i])