How to run an external program in Swift?

Using Swift
1

How to run an external program in Swift?
I'm trying to run a calculator in Swift and I can't!
Note: I'm using Windows:

import Foundation
    let p = Process()
    p.executableURL = URL(fileURLWithPath: "calc")
    try p.run()
2

Would you be able to provide the exact error message that you're seeing?

3

The calculator is not running!

C:\teste.app>swift run teste.app
Building for debugging...
[1/1] Write auxiliary file C:\teste.app.build\x86_64-unknown-windows-msvc\debug\swift-version-7C931827B4E7650F.txt
Build of product 'teste.app' complete! (22.45s)
warning: unable to create symbolic link at C:\teste.app.build\debug: Error Domain=NSCocoaErrorDomain Code=512 "(null)"
error: exec error: No such file or directory (2): C:\teste.app.build\x86_64-unknown-windows-msvc\debug\teste.app .build\x86_64-unknown-windows-msvc\debug\teste.app

4

Which version of Swift are you using? Could you paste the output of swift --version command here?

5

swift --version
Swift version 6.0.3 (swift-6.0.3-RELEASE)
Target: x86_64-unknown-windows-msvc

6

I don't get the same error as you, but you appear to be passing the name of the program that you want to run, instead of its path.

Try this instead:

p.executableURL = URL(fileURLWithPath: "/Windows/System32/calc.exe")

That works for me (on a virtualised copy of Windows.)

7

It's still giving an error! I'll see if reinstalling Swift on Windows will make the error go away! I'll reinstall it on Windows tomorrow!

Any installation tips?

import Foundation

    let p = Process()
    p.executableURL = URL(fileURLWithPath: "/Windows/System32/calc.exe")
    try p.run()

Error:

C:\teste.app>swift run teste.app
Building for debugging...
[5/5] Compiling teste_app main.swift
Build of product 'teste.app' complete! (34.45s)
warning: unable to create symbolic link at C:\teste.app.build\debug: Error Domain=NSCocoaErrorDomain Code=512 "(null)"
error: exec error: No such file or directory (2): C:\teste.app.build\x86_64-unknown-windows-msvc\debug\teste.app .build\x86_64-unknown-windows-msvc\debug\teste.app

8

I think that it maybe because your project has a full-stop (period) in the name: teste.app - why did you give it an .app suffix, out of curiosity?

I tried making a swift executable package on Windows with a matching name and then moving into the package directory and running swift run and it wasn't happy, although the executable was built.

Building for debugging...
[8/8] Linking C:\Users\diggory\test.app\.build\aarch64-unknown-windows-msvc\debug\test.app.exe
Build of product 'test.app' complete! (4.27s)
error: exec error: No such file or directory (2): C:\Users\diggory\test.app\.build\aarch64-unknown-windows-msvc\debug\test.app .build\aarch64-unknown-windows-msvc\debug\test.app
9

It seems like URL(fileURLWithPath:) will give you the URL relative to the current directory. I don't think this is what you want though. Try this:

import Foundation
let calc = URL(string: "file:///c:/Windows/System32/calc.exe")!
_ = try calc.checkResourceIsReachable()

Also I'd take a look at RFC 8089 - The "file" URI Scheme.

10

I was able to open the calculator!
But when I insert these parameters of the Java code, I can't open the program!
The parameters are:

c:/java/jdk-23/bin/java.exe -jar /java-exec/WindowJAR.jar

How can I run the program with the addition of these parameters?

import Foundation

let p = Process()
p.executableURL = URL(string: "file:///c:/java/jdk-23/bin/java.exe -jar /java-exec/WindowJAR.jar")
try p.run()

Error

C:\teste>swift run teste
Building for debugging...
[8/8] Linking C:\teste\.build\x86_64-unknown-windows-msvc\debug\teste.exe
Build of product 'teste' complete! (52.91s)
warning: unable to create symbolic link at C:\teste\.build\debug: Error Domain=NSCocoaErrorDomain Code=512 "(null)"
Swift/ErrorType.swift:253: Fatal error: Error raised at top level: Error Domain=NSCocoaErrorDomain Code=260 "The file doesn’t exist."
Current stack trace:
0    swiftCore.dll                      0x00007ff855c50e70 swift_stdlib_reportFatalErrorInFile + 132
1    swiftCore.dll                      0x00007ff85588ad80 StaticString.withUTF8Buffer<A>(_:) + 1172
2    swiftCore.dll                      0x00007ff85588ad80 StaticString.withUTF8Buffer<A>(_:) + 626
3    swiftCore.dll                      0x00007ff855889d50 _assertionFailure(_:_:file:line:flags:) + 372
4    swiftCore.dll                      0x00007ff8558ffcd0 swift_errorInMain + 960
5    teste.exe                          0x00007ff6825f12b0 main + 190
6    teste.exe                          0x00007ff6825f12b0 main + 832
7    KERNEL32.DLL                       0x00007ff8dc59e8c0 BaseThreadInitThunk + 23
8    ntdll.dll                          0x00007ff8dde7bf40 RtlUserThreadStart + 44
11

You get this error because it's going to look for a file with the path c:/java/jdk-23/bin/java.exe -jar /java-exec/WindowJAR.jar which doesn't exist. Your executableUrl is just URL(string: "file:///c:/java/jdk-23/bin/java.exe), the rest are arguments e.g.,

let p = Process()
p.executableURL = URL(string: "file:///c:/myExecutable.exe")
p.arguments = ["-s", "path/to/some/file"]

However for /java-exec/... make sure you pass the absolute path.

Also, if you want avoid throwing an error at the top level you can wrap your p.run() in a do-catch:

import Foundation
let p = Process()
p.executableURL = URL(string: "file:///foo")!
do {
  try p.run()
} catch {
  print("Error:", error.localizedDescription)
}

EDIT: Added note about error handling.

12

Solved!
Thanks everyone for helping me!

import Foundation

let p = Process()
p.executableURL = URL(string: "file:///c:/java/jdk-23/bin/java.exe")
p.arguments = ["-jar", "/java-exec/WindowJAR.jar"]

do {
try p.run()
} catch {
print("Error:", error.localizedDescription)
}
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