Commandline arguments

Programming Workshop 2 (CSCI 1061U)

Faisal Qureshi

Faculty of Science, UOIT

http://vclab.science.uoit.ca


C++ main() function is able to accept command line arguments as follows

int main(int argc, char* argv[])
{
    ...
}

argc stores the count, i.e., the number of elements in the char* array. argv is the char* array that stores the individual arguments.

argv[0] is always the fullname (/path/program_name) of the program.

The following code prints the command line arguments passed to the program.

#include <iostream>

using namespace std;

int main(int argc, char* argv[])
{
  cout << "argc = " << argc << endl;

  for (int i=0; i<argc; ++i) {
    cout << "argv[" << i << "] = " << argv[i] << endl;
  }
  
  return 0;
}

You are not forced to use argc and argv as identifiers in main(). These are simply the established conventions.

An alternate way to declare argv is

int main(int argc, char** argv)
{
    ...
}

Command line only returns character array. It's your responsibility to convert these into appropriate form. E.g., atoi(), atof() and atol can be used to convert a "valid" string to int, float and double.

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