Command line app: Unix cd command

Question

My Mac OS command line application is making Unix calls such as:

system("rm -rf /Users/stu/Developer/file);

perfectly successfully.

So why is the following not changing the current directory?

system("cd /Users/me/whatever");
system("pwd");    //cd has not changed

Answer 1

Because

system() executes a command specified in command by calling /bin/sh -c command , and returns after the command has been completed.

So each command is executed independently, each in a new instance of the shell.

So your first call spawns a new sh (with your current working directory), changes directories, and then exits. Then the second call spawns a new sh (again in your CWD).

See the man page for system() .

---

The better solution is to not use system . It has some inherent flaws that can leave you open to security vulnerabilities. Instead of executing system() commands, you should use the equivalent POSIX C functions. Everything that you can do from the command-line, you can do with C functions (how do you think those utilities work?)

• Instead of system("rm -rf ...") use this .
• Instead of system("cd ...") use chdir() .
• Instead of system("pwd ...") use getcwd() .

There are some differences, of course, but these are the fundamental equivalents of what you're trying to do.