sysProcess.md

SysProcess

Perfect provides the ability to execute local processes or shell commands through the SysProcess type. This type allows local processes to be launched with an array of parameters and shell variables. Some processes will execute and return a result immediately. Other processes can be left open for interactive read/write operations.

Relevant Examples

• Perfect-System

Setup

Add the "Perfect" project as a dependency in your Package.swift file:

.Package(
	url: "https://github.com/PerfectlySoft/PerfectLib.git",
	majorVersion: 3
	)

In your file where you wish to use SysProcess, import the PerfectLib and add either SwiftGlibc or Darwin:

import PerfectLib

#if os(Linux)
	import SwiftGlibc
#else
	import Darwin
#endif

Executing a SysProcess Command

The following function runProc accepts a command, an array of arguments, and optionally outputs the response from the command.

func runProc(cmd: String, args: [String], read: Bool = false) throws -> String? {
	let envs = [("PATH", "/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin")]
	let proc = try SysProcess(cmd, args: args, env: envs)
	var ret: String?
	if read {
		var ary = [UInt8]()
		while true {
			do {
				guard let s = try proc.stdout?.readSomeBytes(count: 1024) where s.count > 0 else {
					break
				}
				ary.append(contentsOf: s)
			} catch PerfectLib.PerfectError.fileError(let code, _) {
				if code != EINTR {
					break
				}
			}
		}
		ret = UTF8Encoding.encode(bytes: ary)
	}
	let res = try proc.wait(hang: true)
	if res != 0 {
		let s = try proc.stderr?.readString()
		throw  PerfectError.systemError(Int32(res), s!)
	}
	return ret
}

let output = try runProc(cmd: "ls", args: ["-la"], read: true)
print(output)

Note that the SysProcess command is executed in this example with a hardcoded environment variable.

SysProcess Members

stdin

stdin is the standard input file stream.

stdout

stdout is the standard output file stream.

stderr

stderr is the standard error file stream.

pid

pid is the process identifier.

SysProcess Methods

isOpen

Returns true if the process was opened and was running at some point.

Note that the process may not be currently running. Use wait(false) to check if the process is currently running.

myProcess.isOpen()

close

close terminates the process and cleans up.

myProcess.close()

detach

Detach from the process such that it will not be manually terminated when this object is uninitialized.

myProcess.detach()

wait

Determine if the process has completed running and retrieve its result code.

myProcess.wait(hang: <Bool>)

kill

Terminate the process and return its result code.

myProcess.kill(signal: <Int32 = SIGTERM>)

Response is an Int32 result code.