Split subprocess API into util/

Author: mgorny

Makefile.am

@@ -53,4 +53,6 @@ eclean_kernel_SOURCES = \
 	src/ek2/util/error.h \
 	src/ek2/util/relativepath.cxx \
 	src/ek2/util/relativepath.h \
+	src/ek2/util/subprocess.cxx \
+	src/ek2/util/subprocess.h \
 	src/main.cxx

src/ek2/bootloaders/grub2.cxx

@@ -12,6 +12,7 @@
 #include "ek2/util/directorystream.h"
 #include "ek2/util/error.h"
 #include "ek2/util/relativepath.h"
+#include "ek2/util/subprocess.h"
 
 #include <cerrno>
 #include <cstring>
@@ -23,7 +24,6 @@ extern "C"
 {
 #	include <fcntl.h>
 #	include <unistd.h>
-#	include <sys/wait.h>
 };
 
 static const char grub2_autogen_header[] =
@@ -115,51 +115,19 @@ void GRUB2::postrm()
 	// we should update it
 	if (is_autogenerated_)
 	{
-		// TODO: move this to util/
-		// love the C exec*() API
-		std::vector<std::string> argv{"grub-mkconfig",
+		std::vector<std::string> argv{
 			is_multislot_ ? "grub2-mkconfig" : "grub-mkconfig",
 			"-o", grub_cfg_->path()};
-		std::vector<std::vector<char>> argv_rw;
-		std::vector<char*> cargv;
 
 		if (opts_.pretend)
 		{
 			std::cerr << "\nThe following command would be run: "
-				<< argv[1] << " " << argv[2] << " " << argv[3] << std::endl;
+				<< argv[0] << " " << argv[1] << " " << argv[2] << std::endl;
 			return;
 		}
 
-		std::cerr << "\nRunning: " << argv[1] << " " << argv[2]
-			<< " " << argv[3] << std::endl;
-
-		for (const std::string& s : argv)
-		{
-			// std::string -> std::vector<char>
-			argv_rw.emplace_back(s.begin(), s.end());
-			argv_rw.back().push_back('\0');
-
-			// std::vector<char> -> char*
-			cargv.push_back(argv_rw.back().data());
-		}
-		// sentinel
-		cargv.push_back(nullptr);
-
-		pid_t child_pid = fork();
-		switch (child_pid)
-		{
-			case -1:
-				throw IOError("fork() failed", errno);
-				break;
-			case 0:
-				std::cerr << cargv[0] << "\n";
-				execvp(cargv[0], cargv.data());
-				std::cerr << "Failed to execute " << cargv[0]
-					<< ": " << strerror(errno) << std::endl;
-				_exit(1);
-				break;
-			default:
-				waitpid(child_pid, nullptr, 0);
-		}
+		std::cerr << "\nRunning: " << argv[0] << " " << argv[1]
+			<< " " << argv[2] << std::endl;
+		run_subprocess(argv);
 	}
 }

src/ek2/util/subprocess.cxx

@@ -0,0 +1,60 @@
+/* eclean-kernel2
+ * (c) 2017 Michał Górny
+ * 2-clause BSD license
+ */
+
+#ifdef HAVE_CONFIG_H
+#	include "config.h"
+#endif
+
+#include "ek2/util/subprocess.h"
+
+#include "ek2/util/error.h"
+
+extern "C"
+{
+#	include <unistd.h>
+#	include <sys/wait.h>
+};
+
+#include <cerrno>
+#include <cstring>
+#include <iostream>
+#include <string>
+#include <vector>
+
+void run_subprocess(const std::vector<std::string>& argv)
+{
+	std::vector<std::vector<char>> argv_rw;
+	std::vector<char*> cargv;
+
+	for (const std::string& s : argv)
+	{
+		// std::string -> std::vector<char>
+		argv_rw.emplace_back(s.begin(), s.end());
+		argv_rw.back().push_back('\0');
+
+		// std::vector<char> -> char*
+		cargv.push_back(argv_rw.back().data());
+	}
+	// sentinel
+	cargv.push_back(nullptr);
+
+	pid_t child_pid = fork();
+	switch (child_pid)
+	{
+		case -1:
+			throw IOError("fork() failed", errno);
+			break;
+		case 0:
+			std::cerr << cargv[0] << "\n";
+			execvp(cargv[0], cargv.data());
+			std::cerr << "Failed to execute " << cargv[0]
+				<< ": " << strerror(errno) << std::endl;
+			_exit(1);
+			break;
+		default:
+			// TODO: handle EINTR
+			waitpid(child_pid, nullptr, 0);
+	}
+}

src/ek2/util/subprocess.h

@@ -0,0 +1,19 @@
+/* eclean-kernel2
+ * (c) 2017 Michał Górny
+ * 2-clause BSD license
+ */
+
+#pragma once
+
+#ifndef EK2_UTIL_SUBPROCESS_H
+#define EK2_UTIL_SUBPROCESS_H 1
+
+#include <string>
+#include <vector>
+
+// run subprocess and wait for its termination (alike system())
+// argv[0] is assumed to contain the program name, argv[1..n] params
+// (execvp() is used)
+void run_subprocess(const std::vector<std::string>& argv);
+
+#endif /*EK2_UTIL_SUBPROCESS_H*/