#include <stdio.h>
#include <stdlib.h>
#include <windows.h>

char*mytmpfile="notrail.tmp";

void err(char*text){
 if(!text)text="Can't open file";
 MessageBox(
  0,
  text,
  "NoTrail Error",
  MB_ICONERROR | MB_OK
 );
 exit(1);
}


static inline void replace(char*s){
 remove(s);
 rename(mytmpfile,s);
}


static inline void notrail(char*filename){
 FILE*i,*o;
 unsigned long int saved=0;
 unsigned long int n;
 int c;
 int b;
 i=fopen(filename,"rt");
 if(!i)err(0);
 o=fopen(mytmpfile,"wt");
 if(!o)err(0);
 do{
  c=getc(i);
  if(c==EOF)break;
  if(c==32){
   n=1;
   while((c=getc(i))==32)++n;
   if(c!='\n'&&c!=EOF){
    do putc(' ',o);
    while(--n);
   }else saved+=n;
  }
  b=c!=EOF;
  if(b)putc(c,o);
 }while(b);
 fclose(o);
 fclose(i);
 if(saved){
  char text[32];
  sprintf(text,"Saved %lu bytes\n",saved);
  n=MessageBox(
   0,
   text,
   filename,
   MB_ICONASTERISK | MB_OKCANCEL
  );
  if(n==IDOK){
   replace(filename);
   return;
  }
 }
 remove(mytmpfile);
}


int main(int argc,char**argv){
 if(argc<2){
  MessageBox(
   0,
   "Removes trailing blanks. To use, close this"
   " window and drag and drop one or more"
   " files onto the program's icon.",
   "NoTrail by Zufolek 2009",
   MB_ICONINFORMATION | MB_OK
  );
  return 0;
 }
 while(--argc)notrail(*++argv);
 return 0;
}

Simple prog for removing trailing blanks. Not for use with binary, compressed, or encoded files. Please make backups of your files.

Remove trailing blanks from files

C