From 5bf6503ed1d3f4ff905630dbc242118ec00401f8 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Fri, 26 Nov 2021 15:54:05 +0100
Subject: [PATCH] cat: Use TRY() and LibCore syscall wrappers a lot more :^)

---
 Userland/Utilities/cat.cpp | 49 +++++++++++++++++---------------------
 1 file changed, 22 insertions(+), 27 deletions(-)

diff --git a/Userland/Utilities/cat.cpp b/Userland/Utilities/cat.cpp
index 78b1043725..c749cbeff5 100644
--- a/Userland/Utilities/cat.cpp
+++ b/Userland/Utilities/cat.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -8,13 +8,14 @@
 #include <LibCore/ArgsParser.h>
 #include <LibCore/System.h>
 #include <LibMain/Main.h>
-#include <errno.h>
 #include <fcntl.h>
-#include <stdio.h>
-#include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
 
+#define IFTRY(binding, expression)                                              \
+    if (auto _temporary_result = (expression); !_temporary_result.is_error()) { \
+        auto binding = _temporary_result.release_value();
+
 ErrorOr<int> serenity_main(Main::Arguments arguments)
 {
     TRY(Core::System::pledge("stdio rpath", nullptr));
@@ -27,44 +28,38 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     args_parser.parse(arguments);
 
     Vector<int> fds;
-    if (!paths.is_empty()) {
+    if (paths.is_empty()) {
+        TRY(fds.try_append(STDIN_FILENO));
+    } else {
         for (auto const& path : paths) {
             int fd;
             if (path == "-") {
                 fd = 0;
-            } else if ((fd = open(path.characters(), O_RDONLY)) == -1) {
-                warnln("Failed to open {}: {}", path, strerror(errno));
-                continue;
+            } else {
+                auto fd_or_error = Core::System::open(path, O_RDONLY);
+                if (fd_or_error.is_error()) {
+                    warnln("Failed to open {}: {}", path, fd_or_error.error());
+                    continue;
+                }
+                fd = fd_or_error.release_value();
             }
-            fds.append(fd);
+            TRY(fds.try_append(fd));
         }
-    } else {
-        fds.append(0);
     }
 
     TRY(Core::System::pledge("stdio", nullptr));
 
     for (auto& fd : fds) {
         for (;;) {
-            char buf[32768];
-            ssize_t nread = read(fd, buf, sizeof(buf));
+            char buffer[32768];
+            auto nread = TRY(Core::System::read(fd, buffer, sizeof(buffer)));
             if (nread == 0)
                 break;
-            if (nread < 0) {
-                perror("read");
-                return 2;
-            }
-            size_t already_written = 0;
-            while (already_written < (size_t)nread) {
-                ssize_t nwritten = write(1, buf + already_written, nread - already_written);
-                if (nwritten < 0) {
-                    perror("write");
-                    return 3;
-                }
-                already_written += nwritten;
-            }
+            ssize_t already_written = 0;
+            while (already_written < nread)
+                already_written += TRY(Core::System::write(STDOUT_FILENO, buffer + already_written, nread - already_written));
         }
-        close(fd);
+        TRY(Core::System::close(fd));
     }
 
     return 0;