Contribute to regishsu/SpiderRobot development by creating an account on GitHub. Dismiss Join GitHub today. GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. Two colons mean an option takes an optional arg; if there is text in the current argv-element (i.e., in the same word as the option name itself, for example, "-oarg"), then it is returned in optarg, otherwise optarg is set to zero. This is a GNU extension. What is atoi()? atoi() is a library function that converts string to integer, when program gets the input from command line, string values transfer in the program, we have to convert them to integers (in this program). atoi() is used to return the integer of the string arguments. Detailed Description. This module is dedicated to square fiducial markers (also known as Augmented Reality Markers) These markers are useful for easy, fast and robust camera pose estimation.ç Jan 30, 2013 · Here, argc parameter is the count of total command line arguments passed to executable on execution (including name of executable as first argument). argv parameter is the array of character string of each command line argument passed to executable on execution.