Using command line arguments to extract from txt file and run specific classes in C++

Question

I'm working on a project that needs to be run with either of the following commands:

./project.exe -Stack < [filename]

./project.exe -Queue < [filename]

I am wondering why there is a - in front of both Stack and Queue and why the filename is preceded by < and is in brackets.

The purpose of this format is to tell the program to either run using a stack class or run using a queue class. I will also need to extract the information from the text file mentioned in the command line.

I am familiar with general command line arguments and how to use them, but I have never seen this notation before and can't find any clear explanations.

Answer 1

The dash for the options are simply a common convention. Usually with modern command-line programs one uses double-dash for so-called long options (like e.g. --stack) and single dash for short options (e.g. -s).

Many existing argument parsers, like the Linux getopt_long function, actually requires the single or double dashes for short and long options to be recognized as such.

The < is file redirection. It tells the shell to redirect the programs standard input from the file. Inside the program you can read from standard input (std::cin) and it will be automatically reading from the file. This redirection is handled entirely by the shell.