Add kill and poll features for processes

include/linuxdeploy/subprocess/process.h

@@ -1,6 +1,7 @@
 // system headers
 #include <unordered_map>
 #include <vector>
+#include <signal.h>
 
 // local headers
 #include "linuxdeploy/subprocess/subprocess.h"
@@ -62,10 +63,22 @@ namespace linuxdeploy {
             int stderr_fd() const;
 
             /**
-             * Close all pipes and wait for process to exit. If process was closed already, just returns exit code.
+             * Close all pipes and wait for process to exit.
+             * If process is not running any more, just returns exit code.
              * @return child process's exit code
              */
             int close();
+
+            /**
+             * Kill underlying process with given signal. By default, SIGTERM is used to end the process.
+             */
+            void kill(int signal = SIGTERM) const;
+
+            /**
+             * Check whether process is still alive. Use close() to fetch exit code.
+             * @return true while process is alive, false otherwise
+             */
+            bool poll();
         };
     }
 }

src/subprocess/process.cpp

@@ -54,8 +54,6 @@ process::process(const std::vector<std::string>& args, const subprocess_env_map_
         throw std::runtime_error{"fork() failed"};
     }
 
-    std::cout << "child pid: " << std::to_string(child_pid_) << std::endl;
-
     if (child_pid_ == 0) {
         // we're in the child process
 
@@ -190,3 +188,24 @@ std::vector<char*> process::make_env_vector_(const subprocess_env_map_t& env) {
 
     return rv;
 }
+
+void process::kill(int signal) const {
+    if (::kill(child_pid_, signal) != 0) {
+        throw std::logic_error{"failed to kill child process"};
+    }
+}
+
+bool process::poll() {
+    if (exited_) {
+        return false;
+    }
+
+    int temporary;
+
+    if (waitpid(child_pid_, &temporary, WNOHANG) != 0) {
+        return true;
+    }
+
+    exit_code_ = WEXITSTATUS(temporary);
+    return false;
+}