$ add num num<ENTER>
$ sub num num<ENTER>
$ mul num num<ENTER>
$ div num num<ENTER>
// command.cpp
#include "stdlib.h"
#include <iostream>
using namespace std;
int main(int argc,char* argv[]){
char comm[100]="calculate";
int i;
if(argc < 3)
{
cout <<"ERROR: Please enter the command followed by two numeric at least...\n" << endl;
return 1;
}
for (i = 0; i < argc; argv++, i++){
strcat(comm, " ");
strcat(comm,*argv);
}
system(comm);
return 0;
}
// after compile command.cpp, copy "command.exe" file to "add.exe, sub.exe, mul.exe,div.exe"; or alias command in the Linux bash shell.
//calculate.cpp
#include "ctype.h"
#include <iostream>
using namespace std;
void cal(int argn,char* argvc[]);
void results(double);
int main(int argc,char* argv[]){
if (argc > 3)
cal(argc,argv);
else
cout << "ERROR: Invaild Command."<<endl;
return 0;
}
void cal(int argn,char* argvc[]){
double re = 0;
int i;
if ( strcmp(*(argvc+1),"add")==0){
for( i = 2; i < argn ; i++){
if (i > 2) cout << " + ";
if (i > 0) cout << argvc[i];
re += atoi(argvc[i]);
}
}
else if ( strcmp(*(argvc+1),"sub")==0){
re = (atoi(argvc[2])*2);
for( i = 2; i < argn ; i++){
if (i > 2) cout << " - ";
if (i > 0) cout << argvc[i];
re -= atoi(argvc[i]);
}
}
else if ( strcmp(*(argvc+1),"mul")==0){
re = 1;
for( i = 2; i < argn ; i++){
if (i > 2) cout << " * ";
if (i > 0) cout << argvc[i];
re *= atoi(argvc[i]);
}
}
else if ( strcmp(*(argvc+1),"div")==0){
re = atoi(argvc[2]);
re *= re;
for( i = 2; i < argn ; i++){
if (i > 2) cout << " / ";
if (i > 0) cout << argvc[i];
re /= atoi(argvc[i]);
}
}
results(re);
}
void results(double re){
cout << " = " << re << endl;
}
2. write a program to show the content of an Operating system environment variable
$ pnenvr path
The output will be either the "content" of path variable or "not found" if the environment variable does not exist.
//Show the content of an Os environment variable
#include <string>
#include <iostream>
#include <cctype>
#include <algorithm>
using namespace std;
int main(int argc, char* argv[], char* env[]){
int i;
string s1(argv[1]);
string s2;
string token("=");
bool find=false;
s1.append(token);
transform(s1.begin(), s1.end(), s1.begin(), ::toupper);
for(i=0;env[i] != 0;i++){
s2=env[i];
transform(s2.begin(), s2.end(), s2.begin(), ::toupper);
s2=s2.substr(0,s1.length());
if (s2 == s1) {
find=true;
cout << env[i] << endl;
break;
}
}
if (find != true)
cout << "Not found" ;
return 0;
}
