Change your Mac's screen resolution from the command line.

screenres.swift

#!/usr/bin/swift

import Foundation

var shouldPrintUsage = true
var shouldPrintModes = true
var shouldSwitchMode = false
var didSwitchMode = false
var desiredDisplayNumber: Int? = nil
var desiredWidth: Int? = nil
var desiredHeight: Int? = nil
var desiredRefreshRate: Double? = nil

if Process.arguments.count > 1 {
    desiredDisplayNumber = Int(Process.arguments[1])
}
if Process.arguments.count > 2 {
    desiredWidth = Int(Process.arguments[2])
    shouldSwitchMode = true
    shouldPrintUsage = false
    shouldPrintModes = false
}
if Process.arguments.count > 3 {
    desiredHeight = Int(Process.arguments[3])
}
if Process.arguments.count > 4 {
    desiredRefreshRate = Double(Process.arguments[4])
}

if shouldPrintUsage {
    print("Usage: \(Process.arguments[0]) [<displayNumber> <width>] [<height>] [<refreshRate>]")
    print("If no arguments are specified, then a list of available modes for each display will be printed.")
    print("If you specify a displayNumber and width (and optionally height and refreshRate) then that display will switch to the first mode that matches the values you specified.")
    print("After switching to a new mode, press Enter to quit the program and revert back to the default display mode.")
}

func isDesirableMode(displayNumber: Int, mode: CGDisplayModeRef) -> Bool
{
    if !shouldSwitchMode { return false }
    
    let height = CGDisplayModeGetHeight(mode)
    let width = CGDisplayModeGetWidth(mode)
    let refreshRate = CGDisplayModeGetRefreshRate(mode)
    
    if (desiredWidth == nil || width == desiredWidth) {
        if (desiredHeight == nil || height == desiredHeight) {
            if (desiredRefreshRate == nil || refreshRate == desiredRefreshRate) {
                return true
            }
        }
    }
    return false
}

let MAX_DISPLAYS : UInt32 = 32

var displays: [CGDirectDisplayID] = []
for i in 0 ..< Int(MAX_DISPLAYS) { displays.append(0) }

var numDisplays: UInt32 = 0

CGGetActiveDisplayList (MAX_DISPLAYS, &displays, &numDisplays)

if numDisplays == 0 {
    print("ERROR: No displays found")
    exit(1)
}

for displayNumber in 0 ..< Int(numDisplays)
{
    if shouldPrintModes {
        print("Display: \(displayNumber)")
    }
    guard let modeArray = CGDisplayCopyAllDisplayModes (displays[displayNumber], nil) as [AnyObject]? else {
        print("ERROR: CGDisplayCopyAllDisplayModes returned nil")
        exit(2)
    }
    let count = CFArrayGetCount (modeArray)
    if count == 0 {
        print("WARNING: Display \(displayNumber) has no modes.")
    }
    for modeNumber in 0 ..< count
    {
        let mode = modeArray[modeNumber] as! CGDisplayMode
        
        if shouldPrintModes {
            print("  \(CGDisplayModeGetWidth(mode)) x \(CGDisplayModeGetHeight(mode)) @ \(CGDisplayModeGetRefreshRate(mode)) Hz")
        }
        
        if (isDesirableMode(displayNumber, mode: mode)) {
            CGDisplaySetDisplayMode (displays[displayNumber], mode, nil)
            didSwitchMode = true
            break
        }
    }
}

if didSwitchMode {
    print("Press Enter to revert back to the default display mode.")
    _ = readLine()
}