LibCore+chown: Return ErrorOr<Optional<...>> for getgrnam and getpwnam

This patch returns an empty Optional<...> instead of an Error for
Core::System::getgrname and Core::System::getpwnam if we can't find a
matching group or user entry.

It also updates the 'chown' utility to support this new behavior.

3 files changed, 16 insertions, 8 deletions

diff --git a/Userland/Libraries/LibCore/System.cpp b/Userland/Libraries/LibCore/System.cpp
index 19ad7c9d26..ef46ff3d6e 100644
--- a/Userland/Libraries/LibCore/System.cpp
+++ b/Userland/Libraries/LibCore/System.cpp
@@ -393,7 +393,7 @@ ErrorOr<void> chown(StringView pathname, uid_t uid, gid_t gid)
 #endif
 }
 
-ErrorOr<struct passwd> getpwnam(StringView name)
+ErrorOr<Optional<struct passwd>> getpwnam(StringView name)
 {
     ::setpwent();
     if (errno)
@@ -408,10 +408,10 @@ ErrorOr<struct passwd> getpwnam(StringView name)
     if (errno)
         return Error::from_syscall("getpwnam"sv, -errno);
     else
-        return Error::from_string_literal("getpwnam: Unknown username"sv);
+        return Optional<struct passwd> {};
 }
 
-ErrorOr<struct group> getgrnam(StringView name)
+ErrorOr<Optional<struct group>> getgrnam(StringView name)
 {
     ::setgrent();
     if (errno)
@@ -426,7 +426,7 @@ ErrorOr<struct group> getgrnam(StringView name)
     if (errno)
         return Error::from_syscall("getgrnam"sv, -errno);
     else
-        return Error::from_string_literal("getgrnam: Unknown username"sv);
+        return Optional<struct group> {};
 }
 
 ErrorOr<void> clock_settime(clockid_t clock_id, struct timespec* ts)
diff --git a/Userland/Libraries/LibCore/System.h b/Userland/Libraries/LibCore/System.h
index e86a795469..b27df73ff5 100644
--- a/Userland/Libraries/LibCore/System.h
+++ b/Userland/Libraries/LibCore/System.h
@@ -68,8 +68,8 @@ ErrorOr<struct termios> tcgetattr(int fd);
 ErrorOr<void> tcsetattr(int fd, int optional_actions, struct termios const&);
 ErrorOr<void> chmod(StringView pathname, mode_t mode);
 ErrorOr<void> chown(StringView pathname, uid_t uid, gid_t gid);
-ErrorOr<struct passwd> getpwnam(StringView name);
-ErrorOr<struct group> getgrnam(StringView name);
+ErrorOr<Optional<struct passwd>> getpwnam(StringView name);
+ErrorOr<Optional<struct group>> getgrnam(StringView name);
 ErrorOr<void> clock_settime(clockid_t clock_id, struct timespec* ts);
 ErrorOr<pid_t> posix_spawnp(StringView const path, posix_spawn_file_actions_t* const file_actions, posix_spawnattr_t* const attr, char* const arguments[], char* const envp[]);
 ErrorOr<pid_t> waitpid(pid_t waitee, int* wstatus, int options);
diff --git a/Userland/Utilities/chown.cpp b/Userland/Utilities/chown.cpp
index 08d1c04bbd..85d667baff 100644
--- a/Userland/Utilities/chown.cpp
+++ b/Userland/Utilities/chown.cpp
@@ -42,7 +42,11 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
         new_uid = number.value();
     } else {
         auto passwd = TRY(Core::System::getpwnam(parts[0]));
-        new_uid = passwd.pw_uid;
+        if (!passwd.has_value()) {
+            warnln("Unknown user '{}'", parts[0]);
+            return 1;
+        }
+        new_uid = passwd->pw_uid;
     }
 
     if (parts.size() == 2) {
@@ -51,7 +55,11 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
             new_gid = number.value();
         } else {
             auto group = TRY(Core::System::getgrnam(parts[1]));
-            new_gid = group.gr_gid;
+            if (!group.has_value()) {
+                warnln("Unknown group '{}'", parts[1]);
+                return 1;
+            }
+            new_gid = group->gr_gid;
         }
     }