Operating System 
#include "co/os.h"

The API is in the os namespace; flag::parse is not required.

#Environment Variables

co::string os::env(const char* name);
bool       os::env(const char* name, const char* value);
  • env(name): gets the value of an environment variable; returns an empty string if it does not exist.
  • env(name, value): sets the value of an environment variable. If value is nullptr or an empty string, the variable is deleted. Returns true on success.
  • The value is not UTF-8 transcoded.

#Paths

co::string os::homedir();  // current user's home directory
co::string os::cwd();      // current working directory
co::string os::exepath();  // executable file path
co::string os::exedir();   // directory containing the executable
co::string os::exename();  // executable file name
  • Returns an empty string on failure.
  • On Windows, returns UTF-8, consistent with fs.
  • exename() includes the extension.

#Process and Hardware

int    os::pid();
int    os::cpunum();
size_t os::pagesize();
  • pid(): current process id.
  • cpunum(): number of logical CPU cores.
  • pagesize(): page size (in bytes).

#Signals

typedef void (*sig_handler_t)(int);

sig_handler_t os::signal(int sig, sig_handler_t handler, int flag=0);
  • Just a simple wrapper around ::signal.
  • Returns the old handler.
  • flag is not supported on Windows.

#Executing Commands

bool os::system(const char* cmd);
  • There is no std::string overload; you need to call .c_str() first.
  • On non-Windows, it is based on popen / pclose; output goes directly to the terminal.
  • Returns bool, indicating whether the command executed successfully.

#Example

#include "co/os.h"
#include "co/print.h"

int main() {
    co::println("homedir = ", os::homedir());
    co::println("cwd     = ", os::cwd());
    co::println("exepath = ", os::exepath());
    co::println("pid     = ", os::pid());
    co::println("cpunum  = ", os::cpunum());
    co::println("page    = ", os::pagesize());

    co::println("PATH = ", os::env("PATH"));

    os::env("MY_VAR", "hello");
    co::println("MY_VAR = ", os::env("MY_VAR"));

    os::env("MY_VAR", nullptr);

    os::system("echo hello coost");
    return 0;
}