grep in c++

alrawab · 11-09-2003, 12:41 PM

hi ......
any one can help me to convert this command to c/c++
cat a.txt | grep "Osa" >b.txt

thnx

wapcaplet · 11-09-2003, 03:25 PM

Do you want to run this command from within a C/C++ program, or do you want a C/C++ program that will do the same thing as this command does?

jim mcnamara · 11-10-2003, 12:13 PM

Another answer might be:

Code:

#include <stdlib.h>
int main(int argc, char *argv[]){
      shell("cat a.txt | grep 'Osa' >b.txt");
      return 0;
}

In this case, using the commandline is the most efficient approach.

alrawab · 11-10-2003, 02:57 PM

i know how to use the system command
but need to do that with pure c/c++

jim mcnamara · 11-10-2003, 03:38 PM

Code:

#include <stdlib.h>
#include <string.h>
int main(int argc, char *argv[]){
      FILE *in,
           *out;
      char tmp[256];
      in =fopen("a.txt","r");
      out=fopen("b.txt","w");
      if (in==NULL || out==NULL){
               perror("Error opening input or output file ");
               exit(EXIT_FAILURE);
      }
      
      while(!feof(in)){
             memset(tmp,0x00,sizeof(tmp));
             if(fgets(tmp,255,in)!=NULL){
                  if(strstr(tmp,"Osa")!=NULL){
                     fprintf(out,"%s",tmp);
                  }
             }
      }       
      fclose(in);
      fclose(out);
      return 0;
}

kev82 · 11-11-2003, 10:28 AM

can i ask out of interest why you need to do this? it looks a lot like a programming assignment to me.

jim mcnamara · 11-11-2003, 07:44 PM

I agree - but it's C code which prolly won't win him too many points.

infamous41md · 11-12-2003, 01:29 AM

if you're looking for some good performance as well as teh ability to add such options as -A or -B easily you should use mmap.