input redirection file name c++

Question

I have several arguments to my program and an input file being redirected. i am parsing the arguments (using argc and argv) and the file (using cin). However, I am not able to display the name of the redirected file. For instance, the arguments are-

./procsim -r 2 -f 4 -j 3 -k 2 -l 1 < gcc.100k.trace

and my code to parse the arguments is -

for (int i = 1; i < argc; ++i)
    {
    if (argv[i][0] == '-')
        {
        if (!strcmp(argv[i], "-r"))
        {
            if (i < argc - 1)
            {
                pipeline_parameters[count++] = atoi(argv[i+1]);
                R = atoi(argv[i+1]);
                i = i+1;
            }
        }

        else if (!strcmp(argv[i], "-f"))
        {
            if (i < argc - 1)
            {
                pipeline_parameters[count++] = atoi(argv[i+1]);
                F = atoi(argv[i+1]);
                i = i+1;
            }
        }

and to parse the file, I use cin -

 string line;

while (getline( cin, line))
{
address_arr.push_back(line);
}

I want to read the fie name, which is gcc.100k.trace here. how do i do that? P.S. - I have tried parsing through the arguments, but I'm not able to find it!

Edit: address_arr is a vector of int. pipeline_parameters is an array of int of length 5, to store the arguments. R and F are global variables which store the arguments as well.

Welcome to stackoverflow! Please try to create a Minimal, Complete, and Verifiable example as there is information missing from your example, e.g., what is pipeline_parameters or address_arr? — Nikos Kazazakis
– Nikos Kazazakis, Commented Mar 18, 2017 at 5:56
I don't think you can retrieve the name of the file whose contents were redirected to stdin. Take a look at this answer to another SO post. It may lead you to find an answer to your question. — R Sahu
– R Sahu, Commented Mar 18, 2017 at 6:11

John Zwinck · Accepted Answer · 2017-03-18 06:20:35Z

0

You certainly cannot do it using argc and argv. If there is any hope at all, it may be to call getppid() to get your shell's PID, then read /proc/PPID/fd or proc/PPID/fdinfo and see what files are open there.

This will be a huge nasty hack, and has no place in a production application. There's probably not a good enough reason why you'd need to do this, and no other program in the wild does it.

answered Mar 18, 2017 at 6:20

John Zwinck

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