subprocess_run timeout mutually exclusive outpipe

Author: scivision

+stdlib/subprocess_run.m

@@ -11,8 +11,9 @@
 % * cmd_array: vector of string to compose a command line
 % * opt.env: environment variable struct to set
 % * opt.cwd: working directory to use while running command
-% * opt.stdin: string to pass to subprocess stdin pipe
+% * opt.stdin: string to pass to subprocess stdin pipe - OK to use with timeout
 % * opt.timeout: time to wait for process to complete before erroring (seconds)
+% * opt.outpipe: logical to indicate whether to use pipe for stdout and stderr (mutually exclusive with timeout option)
 %%% Outputs
 % * status: 0 is generally success. -1 if timeout. Other codes as per the
 % program / command run
@@ -37,6 +38,11 @@
   opt.cwd (1,1) string = ""
   opt.stdin (1,1) string = ""
   opt.timeout (1,1) int64 = 0
+  opt.outpipe (1,1) logical = true
+end
+
+if opt.outpipe && opt.timeout > 0
+  error("outpipe and timeout options are mutually exclusive")
 end
 
 %% process instantiation
@@ -81,9 +87,16 @@
 end
 
 %% read stdout, stderr pipes
-stdout = read_stream(h.getInputStream());
-stderr = read_stream(h.getErrorStream());
-
+% like Python subprocess.run, this may block or deadlock if the process writes
+% large amounts of data to stdout or stderr.
+% A better approach is to read each of the streams in a separate thread.
+if opt.outpipe
+  stdout = read_stream(h.getInputStream());
+  stderr = read_stream(h.getErrorStream());
+else
+  stdout = "";
+  stderr = "";
+end
 %% wait for process to complete
 % https://docs.oracle.com/en/java/javase/23/docs/api/java.base/java/lang/Process.html#waitFor()
 
@@ -139,6 +152,7 @@
 end
 msg = strip(msg);
 reader.close()
+stream.close()
 
 end
 

.gitignore

@@ -12,3 +12,4 @@ docs/
 
 test/printer_c.exe
 test/printer_fortran.exe
+test/sleep.exe

buildfile.m

@@ -24,8 +24,9 @@
 end
 
 plan("build_c") = matlab.buildtool.Task(Actions=@subprocess_build_c);
+plan("build_cpp") = matlab.buildtool.Task(Actions=@subprocess_build_cpp);
 plan("build_fortran") = matlab.buildtool.Task(Actions=@subprocess_build_fortran);
-plan("test").Dependencies = ["build_c", "build_fortran"];
+plan("test").Dependencies = ["build_c", "build_cpp", "build_fortran"];
 
 if ~isMATLABReleaseOlderThan("R2024a")
   plan("check") = matlab.buildtool.tasks.CodeIssuesTask(pkg_name, IncludeSubfolders=true, ...
@@ -128,6 +129,39 @@ function subprocess_build_c(context)
 end
 
 
+function subprocess_build_cpp(context)
+
+td = context.Plan.RootFolder + "/test";
+src = td + "/sleep.cpp";
+exe = td + "/sleep.exe";
+
+co = mex.getCompilerConfigurations('c++');
+
+cpp = co.Details.CompilerExecutable;
+
+outFlag = "-o";
+shell = "";
+shell_arg = "";
+msvcLike = ispc && endsWith(cpp, "cl");
+if msvcLike
+  shell = strtrim(co.Details.CommandLineShell);
+  shell_arg = co.Details.CommandLineShellArg;
+  outFlag = "/link /out:";
+end
+
+cmd = join([cpp, src, outFlag, exe]);
+if shell ~= ""
+  cmd = join([shell, shell_arg, cmd]);
+end
+
+[r, m] = system(cmd);
+if r ~= 0
+  warning("failed to build TestSubprocess " + exe + " " + m)
+end
+
+end
+
+
 function subprocess_build_fortran(context)
 
 td = context.Plan.RootFolder + "/test";

example/subprocess_run.java

@@ -0,0 +1,35 @@
+import java.io.BufferedReader;
+import java.io.InputStreamReader;
+import java.io.IOException;
+
+public class Filesystem {
+    public static void main(String[] argv) {
+try {
+
+ProcessBuilder builder = new ProcessBuilder(argv[0]);
+Process process = builder.start();
+
+BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()));
+String line;
+while ((line = reader.readLine()) != null) {
+    System.out.println(line);
+}
+
+
+BufferedReader errorReader = new BufferedReader(new InputStreamReader(process.getErrorStream()));
+while ((line = errorReader.readLine()) != null) {
+    System.err.println(line);
+}
+
+int exitCode = process.waitFor();
+System.out.println("Process exited with code: " + exitCode);
+
+process.destroy();
+
+} catch (IOException | InterruptedException e) {
+// ignore
+}
+
+}
+
+}

test/TestSubprocess.m

@@ -89,16 +89,13 @@ function test_env_run(tc)
 
 function test_timeout(tc)
 import matlab.unittest.constraints.StartsWithSubstring
+import matlab.unittest.constraints.IsFile
 
-timeout = 1;
-
-if ispc
-  c = ["powershell", "-command", "Start-Sleep -s 3"];
-else
-  c = ["sleep", "3"];
-end
+cwd = fileparts(mfilename('fullpath'));
+exe = cwd + "/sleep.exe";
+tc.assumeThat(exe, IsFile, exe + " not found")
 
-[ret, ~, err] = stdlib.subprocess_run(c, "timeout", timeout);
+[ret, ~, err] = stdlib.subprocess_run(exe, timeout=1, outpipe=false);
 
 tc.verifyNotEqual(ret, 0, err)
 tc.verifyThat(err, StartsWithSubstring("Subprocess timeout"))

test/sleep.cpp

@@ -0,0 +1,19 @@
+#include <chrono>
+#include <thread>
+
+#include <cstdlib>
+#include <iostream>
+
+
+int main(int argc, char *argv[]) {
+
+    int milliseconds = (argc > 1) ? std::atoi(argv[1]) : 2000;
+
+    std::cout << "Sleeping for " << milliseconds << " milliseconds..." << std::endl;
+
+    std::this_thread::sleep_for(std::chrono::milliseconds(milliseconds));
+
+    std::cout << "Awake!" << std::endl;
+
+    return EXIT_SUCCESS;
+}