Question

Write a program in C to mimic the “delgroup” command on Linux. This command will delete a group. It has to handle 2 files “passwd” and “shadow”. Both these files will be in some folder specified by an environment variable PFILE. The program has to take all arguments as command line arguments

Answer 1

#include<stdio.h>
#include<string.h>
void main(int arg,char *args[])
{
 int i,found=0,parg,max,len,got,counter=0;
 char path[1000],ppath[1000],p[1000],line[100],linep[100];
 FILE *FILEP1,*FILEP2,*FILET1,*FILET2;
 for(i=1;i<arg;i++)
 {
 if(args[i][0]=='P' && args[i][1]=='F' && args[i][2]=='I' && args[i][3]=='L' && args[i][4]=='E' && args[i][5]=='=')
  {
    found=1;
    parg=i; 
    break;
  }
 }
 if(found==1)
 {
  if(args[parg][6]=='"')
  {
   i=7;
   max=strlen(args[parg])-1; 
  }
  else
  {
   i=6;
   max=strlen(args[parg]); 
  }  
  for(i;i<max;i++)
  {
   path[i-5]=args[parg][i];
  }
  strcpy(ppath,path); 
  strcat(path,"/shadow.txt");
  strcat(ppath,"/passwd.txt"); 
  for(i=1;i<strlen(path);i++)
 {
  path[i-1]=path[i];
 }
 path[i-1]='\0';
 for(i=1;i<strlen(ppath);i++)
 {
  ppath[i-1]=ppath[i];
 }
 ppath[i-1]='\0';
 }
 else
 {
  strcpy(path,"shadow.txt");
  strcpy(ppath,"passwd.txt"); 
 } 


 FILEP1 = fopen(path, "r");
 FILEP2 = fopen(ppath,"r");
 FILET1 = fopen("temp1.txt", "w");
 FILET2 = fopen("temp2.txt", "w");
 if((FILEP1 == NULL) && (FILEP2 == NULL)) 
 {
 
       printf("Error! file not found");


       exit(1);


 }


 
 while(fgets(line, sizeof(line), FILEP1) && fgets(linep, sizeof(linep),FILEP2))
 {
    
   got=0;
   len = strlen(line);
       
   if(len > 0 && line[len-1] == '\n')


   {
            line[--len] = '\0';


   }
   for(i=1;i<arg;i++)
   {
      if(i!=parg && strcmp(line, args[i]) == 0)
      {


        counter++;
        got = 1; 
           


      }
  
 }
   if(got==0)
   {
    strcat(line,"\n");
    fputs(line,FILET1);


 
    fputs(linep,FILET2); 
    printf(line," Deleted Successfully");
   }
   else
   {
    printf(line," Not found!"); 
   }
  }
 
   fclose(FILEP1);
   fclose(FILEP2);
   fclose(FILET1);
   fclose(FILET2);






  printf("Total %d accounts deleted.",counter);
  remove(path);
  remove(ppath);
  rename("temp1.txt",path);
  rename("temp2.txt",ppath);
}

Shadow file

id1

id2

id3

id4

id5

id6

id7

id8

id9

id10

id11

id12

passwd file

pwd1

pwd2

pwd3

pwd4

pwd5

pwd6

pwd7

pwd8

pwd9

pwd10

pwd11

pwd12