What does int argc, char * argv [] mean?

In C or C++ programs, when you run a program from the command line, int argc and char *argv[] are two variables used to receive command-line arguments, serving as parameters to the main function. These parameters provide a way for users to pass input information to the program.

• int argc: This variable represents the number of command-line arguments passed to the program. argc is an abbreviation for 'argument count'. Its value is at least 1, as the first argument is the program name by default.
• char *argv[]: This is a string array used to store the actual argument values. argv is an abbreviation for 'argument vector'. argv[0] is the program name, argv[1] is the first argument passed to the program, and so on, up to argv[argc-1].

Example:

Suppose you have a program named example, and you run it from the command line as:

shell
./example hello world

Here, argc will be 3 because there are three arguments: the program name ./example, hello, and world.

argv[0] will be the string './example', argv[1] will be the string 'hello', and argv[2] will be the string 'world'.

This mechanism is very useful, for example, when you need to pass file names, configuration options, or other data to the program before running it.