What does int argc, char *argv[] mean in C/C++?

In C programming, int argc and char *argv[] are parameters of the main function that allow your program to receive command-line arguments when executed. argc stands for argument count and argv stands for argument vector (or argument values).

Syntax

int main(int argc, char *argv[])
{
    // Program code
    return 0;
}

Parameters

• argc − An integer representing the number of command-line arguments passed to the program (including the program name itself)
• argv[] − An array of character pointers (strings) containing the actual command-line arguments

Example

Here's a complete program that demonstrates how to use argc and argv −

#include <stdio.h>

int main(int argc, char *argv[]) {
    printf("This program has %d arguments:\n", argc);
    
    for (int i = 0; i < argc; i++) {
        printf("argv[%d]: %s\n", i, argv[i]);
    }
    
    return 0;
}

When you compile and run this program with command-line arguments like −

$ ./program hello world

The output will be −

This program has 3 arguments:
argv[0]: ./program
argv[1]: hello
argv[2]: world

Key Points

• argv[0] always contains the program name or path to the executable
• argc is always at least 1 (for the program name)
• Arguments are separated by spaces in the command line
• argv is null-terminated − argv[argc] is always NULL

Conclusion

Command-line arguments provide a way to pass input data to your C programs at runtime. Understanding argc and argv is essential for creating flexible programs that can accept user input from the command line.