LibCore: Add command() utility functions

Add utility functions for executing commands and getting their output.

Libraries/LibCore/CMakeLists.txt

@@ -1,6 +1,7 @@
 set(SOURCES
     ArgsParser.cpp
     ConfigFile.cpp
+    Command.cpp
     DateTime.cpp
     DirIterator.cpp
     ElapsedTimer.cpp

Libraries/LibCore/Command.cpp

@@ -0,0 +1,126 @@
+/*
+ * Copyright (c) 2020, Itamar S. <itamar8910@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "Command.h"
+#include <AK/LogStream.h>
+#include <AK/ScopeGuard.h>
+#include <LibCore/File.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+// #define DBG_FAILED_COMMANDS
+
+namespace Core {
+
+// Only supported in serenity mode because we use `posix_spawn_file_actions_addchdir`
+#ifdef __serenity__
+
+String command(const String& command_string, Optional<LexicalPath> chdir)
+{
+    auto parts = command_string.split(' ');
+    if (parts.is_empty())
+        return {};
+    auto program = parts[0];
+    parts.remove(0);
+    return command(program, parts, chdir);
+}
+
+String command(const String& program, const Vector<String>& arguments, Optional<LexicalPath> chdir)
+{
+    int stdout_pipe[2] = {};
+    int stderr_pipe[2] = {};
+    if (pipe2(stdout_pipe, O_CLOEXEC)) {
+        perror("pipe2");
+        ASSERT_NOT_REACHED();
+    }
+    if (pipe2(stderr_pipe, O_CLOEXEC)) {
+        perror("pipe2");
+        ASSERT_NOT_REACHED();
+    }
+
+    auto close_pipes = ScopeGuard([stderr_pipe, stdout_pipe] {
+        // The write-ends of these pipes are closed manually
+        close(stdout_pipe[0]);
+        close(stderr_pipe[0]);
+    });
+
+    Vector<const char*> parts = { program.characters() };
+    for (const auto& part : arguments) {
+        parts.append(part.characters());
+    }
+    parts.append(nullptr);
+
+    const char** argv = parts.data();
+
+    posix_spawn_file_actions_t action;
+    posix_spawn_file_actions_init(&action);
+    if (chdir.has_value()) {
+        posix_spawn_file_actions_addchdir(&action, chdir.value().string().characters());
+    }
+    posix_spawn_file_actions_adddup2(&action, stdout_pipe[1], STDOUT_FILENO);
+    posix_spawn_file_actions_adddup2(&action, stderr_pipe[1], STDERR_FILENO);
+
+    pid_t pid;
+    if ((errno = posix_spawnp(&pid, program.characters(), &action, nullptr, const_cast<char**>(argv), environ))) {
+        perror("posix_spawn");
+        ASSERT_NOT_REACHED();
+    }
+    int wstatus;
+    waitpid(pid, &wstatus, 0);
+    posix_spawn_file_actions_destroy(&action);
+
+    // close the write-ends so reading wouldn't block
+    close(stdout_pipe[1]);
+    close(stderr_pipe[1]);
+
+    auto read_all_from_pipe = [](int pipe[2]) {
+        auto result_file = Core::File::construct();
+        if (!result_file->open(pipe[0], Core::IODevice::ReadOnly, Core::File::ShouldCloseFileDescription::Yes)) {
+            perror("open");
+            ASSERT_NOT_REACHED();
+        }
+        return String::copy(result_file->read_all());
+    };
+
+    if (WEXITSTATUS(wstatus) != 0) {
+#    ifdef DBG_FAILED_COMMANDS
+        dbg() << "command failed. stderr: " << read_all_from_pipe(stderr_pipe);
+#    endif
+        return {};
+    }
+
+    auto result = read_all_from_pipe(stdout_pipe);
+    if (result.is_null())
+        return "";
+    return result;
+}
+
+#endif
+
+}

Libraries/LibCore/Command.h

@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) 2020, Itamar S. <itamar8910@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/LexicalPath.h>
+#include <AK/Optional.h>
+#include <AK/String.h>
+#include <spawn.h>
+
+namespace Core {
+
+// If the executed command fails, the returned String will be in the null state.
+String command(const String& program, const Vector<String>& arguments, Optional<LexicalPath> chdir);
+String command(const String& command_string, Optional<LexicalPath> chdir);
+
+}