How to set ulimit -n from a golang program?

Go's syscall.Setrlimit function enables setting ulimit -n from within a Go program. This allows for customizing resource limits within the program without making global changes.

Understanding setrlimit

The setrlimit system call sets the resource limits for the current process. It takes two arguments: the resource limit type (RLIMIT_NOFILE) and a pointer to a syscall.Rlimit structure.

Implementing the Solution

Here's a Go program that demonstrates how to set ulimit -n:

package main

import (
    "fmt"
    "syscall"
)

func main() {
    var rLimit syscall.Rlimit
    err := syscall.Getrlimit(syscall.RLIMIT_NOFILE, &rLimit)
    if err != nil {
        fmt.Println("Error Getting Rlimit ", err)
    }
    fmt.Println(rLimit)

    rLimit.Max = 999999
    rLimit.Cur = 999999

    err = syscall.Setrlimit(syscall.RLIMIT_NOFILE, &rLimit)
    if err != nil {
        // Handle the error
    }
}

Considerations and Privileges

Note that setting hard limits requires elevated privileges (CAP_SYS_RESOURCE). Otherwise, the program will encounter an "operation not permitted" error. Non-privileged processes can only set soft limits within the range defined by the hard limits.