A simple script to demonstrate some basics of Swift scripting.

-shell.swift

#!/usr/bin/swift

// shell.swift
// A simple script to demonstrate some basics of Swift scripting.

import Foundation
// Docs: https://developer.apple.com/documentation/foundation
// ...and: https://github.com/apple/swift-corelibs-foundation/blob/master/Docs/Status.md

extension CommandLine {
    // credit: https://stackoverflow.com/a/50035059/5673556
    static func run(_ command: String) -> String {
        let task = Process()
        task.launchPath = "/bin/bash"
        task.arguments = ["-c", command]

        let pipe = Pipe()
        task.standardOutput = pipe
        task.launch()

        let data = pipe.fileHandleForReading.readDataToEndOfFile()
        let output = String(data: data, encoding: .utf8)!

        return output
    }
}

let scriptName = CommandLine.arguments[0]
let currentDir = FileManager.default.currentDirectoryPath
let suffix = (CommandLine.argc > 1) ? ":" : ""
print("\(scriptName) launched from \(currentDir) with \(CommandLine.argc - 1) additional arguments\(suffix)")
if !suffix.isEmpty {
    dump(CommandLine.arguments)
}

var showHidden = false
var maxToPrint = 10
var filenamePattern: NSRegularExpression?
var showPermissions = false

for argument in CommandLine.arguments {
    if argument == "-a" {
        showHidden = true
    } else if argument == "-e" {
        showPermissions = true
    } else if argument.hasPrefix("-m=") {
        let startIndex = argument.index(after: argument.index(of: "=")!)  // TODO: Swift 4.2 renames String.index(of:) to String.firstIndex(of:)
        if let maxCount = Int(argument.suffix(from: startIndex)) {
            maxToPrint = maxCount
        }
    } else if argument.hasPrefix("-p=") {
        let startIndex = argument.index(after: argument.index(of: "=")!)  // TODO: Swift 4.2 renames String.index(of:) to String.firstIndex(of:)
        // Note: we don't support whitespace here yet (even escaped), or quoted patterns (ie. any quotes will be included)
        let pattern = String(argument.suffix(from: startIndex))
        filenamePattern = try? NSRegularExpression(pattern: pattern, options: .caseInsensitive)
    }
}

var numPrinted = 0

func printFiles(path: URL) {
    guard showHidden || !path.lastPathComponent.hasPrefix(".") else {
        return
    }
    guard maxToPrint <= 0 || numPrinted < maxToPrint else {
        return
    }

    var doPrint = true
    if let regex = filenamePattern {
        let filename = path.lastPathComponent
        let filenameNS = NSString(string: path.lastPathComponent)
        if regex.firstMatch(in: String(filename), range: NSRange(location: 0, length: filenameNS.length)) == nil {
            // we still want to recurse on non-matching directories, so wipe the print flag here instead of returning
            doPrint = false
        }
    }

    if doPrint {
        var output = path.path
        if showPermissions {
            let shellOutput = CommandLine.run("ls -lda \(path.path)")
            let columns = shellOutput.split(separator: " ")
            if columns.count > 0 {
                output += " -> \(columns[0])"
            }
        }
        print(output)
        numPrinted += 1
        if numPrinted == maxToPrint {
            print("Maximum output of \(maxToPrint) reached -- use `-m=NUMBER` to set a higher maximum, or `-m=0` for no maximum.")
        }
    }

    if path.hasDirectoryPath {
        var contents = try! FileManager.default.contentsOfDirectory(at: path, includingPropertiesForKeys: nil)
        contents.sort {
            return $0.lastPathComponent.lowercased() <= $1.lastPathComponent.lowercased()
        }
        for item in contents {
            printFiles(path: item)
        }
    }
}

let currentDirectory = URL(fileURLWithPath: FileManager.default.currentDirectoryPath)
printFiles(path: currentDirectory)

.gitattributes

# force linefeed (Unix-style) line endings for all .swift files, to prevent SwiftLint
# vertical_whitespace warnings (and line number mismatches) on Windows host machines
*.swift eol=lf