Creating a hardlink using cgo.

hardlink.go

package main

import (
	"fmt"
	"os"
	"syscall"
)

/*
#include <fcntl.h>
#include <unistd.h>

int _linkat(int olddirfd, const char *oldpath, int newdirfd, const char *newpath, int flags) {
    return linkat(olddirfd, oldpath, newdirfd, newpath, flags);
}
*/
import "C"

func main() {
	osArgs, osArgsLen := os.Args, len(os.Args)
	if osArgsLen != 3 {
		fmt.Println("hardlink: 3 arguments needed")
		os.Exit(1)
	}

	origFile, hlinkFile := osArgs[1], osArgs[2]

	_, err := os.Open(origFile)
	if err != nil {
		if os.IsNotExist(err) {
			fmt.Printf("File %s does not exist\n", origFile)
			os.Exit(1)
		}
		fmt.Printf("Unknown error: %s\n", err.Error())
		os.Exit(1)
	}

	makeHardlink(origFile, hlinkFile)
}

func makeHardlink(origFilePath, newFilePath string) {
	origFilePathC := C.CString(origFilePath)
	newFilePathC := C.CString(newFilePath)
	
	result := C._linkat(C.AT_FDCWD, origFilePathC, C.AT_FDCWD, newFilePathC, 0)
	fmt.Println(result)
	if result < 0 {
		fmt.Print("errno: ")
		fmt.Println(syscall.Errno(-result))
		fmt.Println("Error creating hardlink")
		os.Exit(1)
	}
}