Question

I have a bunch of .cpp files which together process similar data files but of various sizes. For the larger data files I want to do some timing studies on the functions inside the .cpp files.

I would like to suppress the output the results for these big data sets, and only print the timing results. For smaller data sets, I would like to print to the screen to verify algorithm/code correctness.

Rather than repeatedly commenting/uncommenting out the appropriate cout statements and recompiling , I would like to use command line arguments (or some other technique) to selectively suppress output.

Any suggestions? The naive one I can think of is use argc and argv, but I am not sure if they are global variables which can be used by functions across different files.

Answer 1

Your intuition is correct — use the argc and argv values passed into your main function — but they are not global variables. You need to make your information global somehow: I’d recommend parsing the arguments once, and keeping a set of global flags that can easily be queried.

For example:

// In a common header file that gets included in each source file
extern bool g_bFlag1;
extern bool g_bFlag2;
...

// In your main source file
bool g_bFlag1 = false;
bool g_bFlag2 = false;
...
int main(int argc, char **argv)
{
    // Parse command line and store results in global flags
    for (int i = 1; i < argc; i++)
    {
        if (strcmp(argv[i], "--flag1") == 0)
            g_bFlag1 = true;
        else if (strcmp(argv[i], "--flag2") == 0)
            g_bFlag2 = true;
        else
            ;  // etc.
    }
}

// In any other source file:
if (g_bFlag1)
{
    // do stuff if and only if g_bFlag1 is set
}

Then you can pass --flag1 on the command line. For more complicated argument parsing, I’d suggest using a library such as GNU getopt.