C++ Change working Directory from User Input

Question

I'm designing a mock shell program, and I can't quite mimic the "cd" command. I've tried chdir(), but that wasn't working, so I moved on to trying to change the environmental variable "PWD="

Here's what I have, and I think this may be close. (Please, please, correct me if I'm wrong or was closer with chdir())

else if (command == "cd")
        {
            string pathEnv = "PWD=";
            string newDir;
            cin >> newDir;
            pathEnv+=newDir;
            cout << pathEnv << endl;
            putenv(pathEnv.c_str());
        }

Hopefully the command would be 'cd /user/username/folder' and my pathEnv variable would be "PWD=/user/username/folder" which would maybe change the directory?

Any insight is greatly appreciated.

Answer 1

chdir() should be the command you are looking for. Did you use getcwd() to fetch the current working directory after you set it?

---

Here is the code which worked for me.

#include <iostream>
#include <string>
#include <sys/param.h>
#include <unistd.h>

...

if (command == "curr") {
    char buffer[MAXPATHLEN];
    char *path = getcwd(buffer, MAXPATHLEN);
    if (!path) {
        // TODO: handle error. use errno to determine problem
    } else {
        string CurrentPath;
        CurrentPath = path;
        cout << CurrentPath << endl;
    }
} else if (command == "cd") {
    string newDir;
    cin >> newDir;
    int rc = chdir(newDir.c_str());
    if (rc < 0) {
        // TODO: handle error. use errno to determine problem
    }
}

There are three versions of getcwd():

char *getcwd(char *buf, size_t size);
char *getwd(char *buf);
char *get_current_dir_name(void);

please consult the man page in unix for details of usage.

Answer 2

You'll always want to use system calls in your code and not "mock" up what the system may be doing such as changing PWD. If you are on a superior UNIX system you should use chdir or if on a Windows Box, the SetCurrentDirectory call. I'm not a Windows developer, whew, but I found this link. http://msdn.microsoft.com/en-us/library/windows/desktop/aa363806%28v=vs.85%29.aspx