Command Line Arguments in C++

This C++ program illustrates the use of command line arguments. The parameter argc passed to the main of the C++ program contains the number of arguments passed to the main function and the argv parameter contains the pointers to the character strings passed as the command-line arguments. Based on the value of these arguments, the case of the string entered can be changed accordingly.

Here is the source code of the C++ program illustrates the use of command line arguments. The C++ program is successfully compiled and run on a Linux system. The program output is also shown below.

```
/*
```

 * C++ Program to Illustrate Command Line Arguments

```
 */
```
```
 
```
```
#include <iostream>
```
```
#include <cctype>
```
```
#include <string>
```
```
 
```
```
int main(int argc, char* argv[])
```
```
{
```
```
    if (argc < 2)
```
```
    {
```

        std::cout << "Command-line Argument missing " << std::endl;

```
        return 0;
```
```
    }
```
```
    else if (argc == 2)
```
```
    {
```

        if (strcmp(argv[1], "toupper") == 0)

```
        {
```
```
            std::string str;
```
```
 
```

            std::cout << "Enter the string ";

```
            std::cin >> str;
```

            for (int i= 0; i < str.length(); i++)

```
            {
```

                str[i] = toupper(str[i]);

```
            }
```

            std::cout << "The string is now " << str

```
                      << std::endl;
```
```
        }
```

        else if (strcmp(argv[1], "tolower") == 0)

```
        {
```
```
            std::string str;
```
```
 
```

            std::cout << "Enter the string ";

```
            std::cin >> str;
```

            for (int i= 0; i < str.length(); i++)

                str[i] = tolower(str[i]);

            std::cout << "The string is now " << str

```
                      << std::endl;
```
```
        }
```
```
        else
```

            std::cout << "Unmatched second command-line argument"

```
                      << std::endl;   
```
```
    }
```
```
    return 0;       
```
```
}
```

$ a.out toupper
Enter the string programming
The string is now PROGRAMMING
$ ./a.out tolower
Enter the string PROGRAMMING
The string is now programming
$ ./a.out
Command-line Argument missing

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