CLI: Implement exec -d (#852)

Surprised we didn't have this already..

Sources/ContainerCommands/Container/ContainerExec.swift

@@ -34,6 +34,9 @@ extension Application {
         @OptionGroup
         var global: Flags.Global
 
+        @Flag(name: .shortAndLong, help: "Run the process and detach from it")
+        var detach = false
+
         @Argument(help: "Container ID")
         var containerId: String
 
@@ -71,11 +74,24 @@ extension Application {
             config.supplementalGroups.append(contentsOf: additionalGroups)
 
             do {
-                let io = try ProcessIO.create(tty: tty, interactive: stdin, detach: false)
+                let io = try ProcessIO.create(tty: tty, interactive: stdin, detach: self.detach)
                 defer {
                     try? io.close()
                 }
 
+                let process = try await container.createProcess(
+                    id: UUID().uuidString.lowercased(),
+                    configuration: config,
+                    stdio: io.stdio
+                )
+
+                if self.detach {
+                    try await process.start()
+                    try io.closeAfterStart()
+                    print(containerId)
+                    return
+                }
+
                 if !self.processFlags.tty {
                     var handler = SignalThreshold(threshold: 3, signals: [SIGINT, SIGTERM])
                     handler.start {
@@ -84,12 +100,6 @@ extension Application {
                     }
                 }
 
-                let process = try await container.createProcess(
-                    id: UUID().uuidString.lowercased(),
-                    configuration: config,
-                    stdio: io.stdio
-                )
-
                 exitCode = try await io.handleProcess(process: process, log: log)
             } catch {
                 if error is ContainerizationError {

Tests/CLITests/Subcommands/Containers/TestCLIExec.swift

@@ -39,4 +39,72 @@ class TestCLIExecCommand: CLITest {
             return
         }
     }
+
+    @Test func testExecDetach() throws {
+        do {
+            let name = getTestName()
+            try doCreate(name: name)
+            defer {
+                try? doStop(name: name)
+            }
+            try doStart(name: name)
+
+            // Run a long-running process in detached mode
+            let output = try doExec(name: name, cmd: ["sh", "-c", "touch /tmp/detach_test_marker"], detach: true)
+            let containerIdOutput = output.trimmingCharacters(in: .whitespacesAndNewlines)
+            try #require(containerIdOutput == name, "exec --detach should print the container ID")
+
+            // Verify the detached process is running by checking if we can still exec commands
+            var lsActual = try doExec(name: name, cmd: ["ls", "/"])
+            lsActual = lsActual.trimmingCharacters(in: .whitespacesAndNewlines)
+            try #require(lsActual.contains("tmp"), "container should still be running and accepting exec commands")
+
+            // Retry loop to check if the marker file was created by the detached process
+            var markerFound = false
+            for _ in 0..<3 {
+                let (_, _, status) = try run(arguments: [
+                    "exec",
+                    name,
+                    "test", "-f", "/tmp/detach_test_marker",
+                ])
+                if status == 0 {
+                    markerFound = true
+                    break
+                }
+                sleep(1)
+            }
+            try #require(markerFound, "marker file should be created by detached process within 3 seconds")
+
+            try doStop(name: name)
+        } catch {
+            Issue.record("failed to exec with detach in container \(error)")
+            return
+        }
+    }
+
+    @Test func testExecDetachProcessRunning() throws {
+        do {
+            let name = getTestName()
+            try doCreate(name: name)
+            defer {
+                try? doStop(name: name)
+            }
+            try doStart(name: name)
+
+            // Run a long-running process in detached mode
+            let output = try doExec(name: name, cmd: ["sleep", "10"], detach: true)
+            let containerIdOutput = output.trimmingCharacters(in: .whitespacesAndNewlines)
+            try #require(containerIdOutput == name, "exec --detach should print the container ID")
+
+            // Immediately check if the process is running using ps
+            var psOutput = try doExec(name: name, cmd: ["ps", "aux"])
+            psOutput = psOutput.trimmingCharacters(in: .whitespacesAndNewlines)
+            try #require(psOutput.contains("sleep 10"), "detached process 'sleep 10' should be visible in ps output")
+
+            try doStop(name: name)
+        } catch {
+            Issue.record("failed to verify detached process is running \(error)")
+            return
+        }
+    }
 }

Tests/CLITests/Utilities/CLITest.swift

@@ -226,11 +226,14 @@ class CLITest {
         }
     }
 
-    func doExec(name: String, cmd: [String]) throws -> String {
+    func doExec(name: String, cmd: [String], detach: Bool = false) throws -> String {
         var execArgs = [
-            "exec",
-            name,
+            "exec"
         ]
+        if detach {
+            execArgs.append("-d")
+        }
+        execArgs.append(name)
         execArgs.append(contentsOf: cmd)
         let (resp, error, status) = try run(arguments: execArgs)
         if status != 0 {

docs/command-reference.md

@@ -313,7 +313,7 @@ Executes a command inside a running container. It uses the same process flags as
 **Usage**
 
 ```bash
-container exec [--env <env> ...] [--env-file <env-file> ...] [--gid <gid>] [--interactive] [--tty] [--user <user>] [--uid <uid>] [--workdir <dir>] [--debug] <container-id> <arguments> ...
+container exec [--detach] [--env <env> ...] [--env-file <env-file> ...] [--gid <gid>] [--interactive] [--tty] [--user <user>] [--uid <uid>] [--workdir <dir>] [--debug] <container-id> <arguments> ...
 ```
 
 **Arguments**
@@ -321,6 +321,10 @@ container exec [--env <env> ...] [--env-file <env-file> ...] [--gid <gid>] [--in
 *   `<container-id>`: Container ID
 *   `<arguments>`: New process arguments
 
+**Options**
+
+*   `-d, --detach`: Run the process and detach from it
+
 **Process Options**
 
 *   `-e, --env <env>`: Set environment variables (format: key=value)