How to begin Get the book.
Practice problems Quizzes. Command line arguments in C using argc and argv By Alex Allain.
Command-line arguments are given after the name of a program in command-line operating systems like DOS or Linux, and are passed in to the program from the operating system. To use command line arguments in your program, you must first understand the full declaration of the main function, which previously has accepted no arguments.
In fact, main can actually accept two arguments: one argument is number of command line arguments, and the other argument is a full list of all of the command line arguments.
It is the number of arguments passed into the program from the command line, including the name of the program. The array of character pointers is the listing of all the arguments.
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After that, every element number less than argc is a command line argument. You can use each argv element just like a string, or use argv as a two dimensional array.
Command line arguments in C++
How could this be used? Almost any program that wants its parameters to be set when it is executed would use this.
One common use is to write a function that takes the name of a file and outputs the entire text of it onto the screen. Note that the idiom of "assign to a variable, check the value" used below works because the assignment statement evaluates to the value assigned.
It first checks to ensure the user added the second argument, theoretically a file name. The program then checks to see if the file is valid by trying to open it.
After that, we just execute a loop to print out one character at a time from the file. The code is self-explanatory, but is littered with comments; you should have no trouble understanding its operation this far into the tutorial.