Where can I learn how to make a C++ program interact with the Operating System (Linux)

Question

I am a C++ beginner.

I'd like to create small programs that interact with the operating system (using Kubuntu Linux). So far, I have not been able to locate any tutorial or handbook to get C++ to interface with the OS.

In PHP, I can use the command exec() or the backtick operator to launch commands typically executed in a console. How can I do similar things in C++? How can I get my C++ program to execute any other command? How can I get the output of such commands?

Thanks.

Answer 1

You can use system() to execute arbitrary commands but, if you want to easily control the input and output with the program, you should look into popen() .

For even more control, you can look into doing exactly what a shell might do, creating some extra file descriptors, forking to start another process, setting up file descriptors 0, 1 and 2 (input, output and error) in that process to connect them to your original process file descriptors then exec'ing the program you want to control. This isn't for the faint of heart :-)

Answer 2

You can use the system() command in stdlib to execute system commands:

#include <stdlib.h>
int main() {
    system("ls -l");
}

system() returns an int as its return value, but the value of the int is system-dependent. If you try and use a command that doesn't exist, you'll get the standard "no such command" output back, and usually a non-zero return value. (For example, running system("ls -l"); on my Windows XP machine here returns a value of 1.

Answer 3

You can use system() as instructed previously or you can use libraries which provide access to standard POSIX API. unistd.h and The GNU C Library include many functions for OS interaction. The possibilities with these libraries are endless as you can implement the functionalities yourself. A simple example: scan a directory for text files with scandir() and print the contents of the files.