// program to echo strings#include<stdio.h>#include<stdlib.h>#include<string.h>main(int argc,char *argv[10]){   int i;    char token[15],ch;     if((argc==2)&&(argv[1][0]=='$'))//if the commend contain $____  {          strcpy(token,argv[0]); //reconstruct the commond and excecute       strcat(token," ");       strcat(token,argv[1]);       system(token);        exit(0);  }  for(i=1;i<argc;i++)  {    printf("%s ",argv[i]);          //except arg(commond) print all arguments in single line  }   printf("\n");        //back to control;}