Golang: How to use syscall.Syscall on Linux?

Question

There is a very nice description about loading a shared library and calling a function with the syscall package on Windows (https://github.com/golang/go/wiki/WindowsDLLs). However, the functions LoadLibrary and GetProcAddress that are used in this description are not available in the syscall package on Linux. I could not find documentation about how to do this on Linux (or Mac OS).

Thanks for help

Answer 1

Linux syscalls are used directly without loading a library, exactly how depends on which system call you would like to perform.

I will use the Linux syscall getpid() as an example, which returns the process ID of the calling process (our process, in this case).

package main

import (
    "fmt"
    "syscall"
)

func main() {
    pid, _, _ := syscall.Syscall(syscall.SYS_GETPID, 0, 0, 0)
    fmt.Println("process id: ", pid)
}

I capture the result of the syscall in pid, this particular call returns no errors so I use blank identifiers for the rest of the returns. Syscall returns two uintptr and 1 error.

As you can see I can also just pass in 0 for the rest of the function arguments, as I don't need to pass arguments to this syscall.

The function signature is: func Syscall(trap uintptr, nargs uintptr, a1 uintptr, a2 uintptr, a3 uintptr) (r1 uintptr, r2 uintptr, err Errno).

For more information refer to https://golang.org/pkg/syscall/