How to get directory of a file which is called from command line argument?

Question

For example, I am calling my executable in ubuntu:

./foo temp/game1.txt temp/game2 txt

I am using realpath() to find the path to the game1.txt. Using it however will give me the full path including the game1.txt name. For example, it will come out as

/home/ * /Download/temp/game1.txt

I want to erase game1.txt on that string so that I can use the string to use it to output other files in that folder. Two questions.

1. Is realpath() alright to use for this kind of operation? Is there better way?
2. Can someone give me a quick way to erase "game1.txt" so that the string will be "/home/ * /Download/temp/" save in a string format(not char)?

Thank you very much.

Answer 1

Don't really know Linux, but a general way for your second question:

#include <string>
#include <iostream>

int main(){
  std::string fullpath("/home/*/Download/temp/game1.txt");
  size_t last = fullpath.find_last_of('/');
  std::string path = fullpath.substr(0,last+1);

  std::cout << path;
}

See on Ideone .

Answer 2

You can use the dirname function for this: http://linux.die.net/man/3/dirname

Note that dirname will erase the trailing slash (except for the root directory); you'll have to append the slash back in when you append the filename.

Also, you don't actually need to use realpath for this purpose, you could simply use the argument as passed in, dirname will give you "temp" and you can append filenames to that.

Answer 3

 man -S3 dirname

应该做你想做的

Answer 4

The cross-platform solution is

QFileInfo target_file_name(argv[1]);
QString absolute_path = target_file_name.absolutePath() 
// e.g. /home/username/

QString some_other_file = QString("%1/another_file.txt").arg(absolute_path) 
// => /home/username/another_file.txt

Boost.Filesystem can also do this easily. I just find the documentation of QFileInfo easily to navigate.

http://doc.qt.nokia.com/4.6/qfileinfo.html#absolutePath