From 64bb5652a1c6a149a5c5c836ffd2ed8ec2b30aee Mon Sep 17 00:00:00 2001
From: Tim Ledbetter <timledbetter@gmail.com>
Date: Tue, 29 Aug 2023 14:31:34 +0100
Subject: [PATCH] find: Add the `-newer`, `-anewer` and `-cnewer` options

These return true if the last modification time, last access time or
creation time of a file is greater than the given reference file.

If the `-L` option is in use and the given reference file is a
symbolic link then the timestamp of the file pointed to by the
symbolic link will be used.
---
 Base/usr/share/man/man1/find.md | 12 +++++++
 Userland/Utilities/find.cpp     | 59 +++++++++++++++++++++++++++++++++
 2 files changed, 71 insertions(+)

diff --git a/Base/usr/share/man/man1/find.md b/Base/usr/share/man/man1/find.md
index 127e476f18..721d5b7c60 100644
--- a/Base/usr/share/man/man1/find.md
+++ b/Base/usr/share/man/man1/find.md
@@ -52,6 +52,18 @@ space rounded up to the nearest whole unit.
 * `-writable`: Checks if the file is writable by the current user.
 * `-executable`: Checks if the file is executable, or directory is searchable,
 by the current user.
+* `-newer file`: Checks if the file last modification time is greater than that
+  of the specified reference file. If `file` is a symbolic link and the `-L`
+  option is in use, then the last modification time of the file pointed to by
+  the symbolic link is used.
+* `-anewer file`: Checks if the file last access time is greater than that of
+  the specified reference file. If `file` is a symbolic link and the `-L`
+  option is in use, then the last access time of the file pointed to by the
+  symbolic link is used.
+* `-cnewer file`: Checks if the file creation time is greater than that of
+  the specified reference file. If `file` is a symbolic link and the `-L`
+  option is in use, then the creation time of the file pointed to by the
+  symbolic link is used.
 * `-print`: Outputs the file path, followed by a newline. Always evaluates to
   true.
 * `-print0`: Outputs the file path, followed by a zero byte. Always evaluates to
diff --git a/Userland/Utilities/find.cpp b/Userland/Utilities/find.cpp
index 8f1646eeeb..b0683952bd 100644
--- a/Userland/Utilities/find.cpp
+++ b/Userland/Utilities/find.cpp
@@ -9,6 +9,7 @@
 #include <AK/LexicalPath.h>
 #include <AK/NonnullOwnPtr.h>
 #include <AK/OwnPtr.h>
+#include <AK/Time.h>
 #include <AK/Vector.h>
 #include <LibCore/System.h>
 #include <LibMain/Main.h>
@@ -326,6 +327,52 @@ private:
     mode_t m_mode { 0 };
 };
 
+class NewerCommand final : public StatCommand {
+public:
+    enum class TimestampType {
+        LastAccess,
+        Creation,
+        LastModification
+    };
+
+    NewerCommand(char const* arg, TimestampType timestamp_type)
+    {
+        auto stat_function = g_follow_symlinks ? Core::System::stat : Core::System::lstat;
+        auto stat_or_error = stat_function({ arg, strlen(arg) });
+        if (stat_or_error.is_error())
+            fatal_error("find: '{}': {}", arg, strerror(stat_or_error.error().code()));
+
+        m_reference_file_stat = stat_or_error.release_value();
+        m_timestamp_type = timestamp_type;
+    }
+
+private:
+    virtual bool evaluate(struct stat const& stat) const override
+    {
+        struct timespec current_file_timestamp;
+        struct timespec reference_file_timestamp;
+        switch (m_timestamp_type) {
+        case TimestampType::LastAccess:
+            current_file_timestamp = stat.st_atim;
+            reference_file_timestamp = m_reference_file_stat.st_atim;
+            break;
+        case TimestampType::Creation:
+            current_file_timestamp = stat.st_ctim;
+            reference_file_timestamp = m_reference_file_stat.st_ctim;
+            break;
+        case TimestampType::LastModification:
+            current_file_timestamp = stat.st_mtim;
+            reference_file_timestamp = m_reference_file_stat.st_mtim;
+            break;
+        }
+
+        return Duration::from_timespec(current_file_timestamp) > Duration::from_timespec(reference_file_timestamp);
+    }
+
+    struct stat m_reference_file_stat;
+    TimestampType m_timestamp_type { TimestampType::LastModification };
+};
+
 class PrintCommand final : public Command {
 public:
     PrintCommand(char terminator = '\n')
@@ -488,6 +535,18 @@ static OwnPtr<Command> parse_simple_command(Vector<char*>& args)
         return make<AccessCommand>(W_OK);
     } else if (arg == "-executable") {
         return make<AccessCommand>(X_OK);
+    } else if (arg == "-newer") {
+        if (args.is_empty())
+            fatal_error("-newer: requires additional arguments");
+        return make<NewerCommand>(args.take_first(), NewerCommand::TimestampType::LastModification);
+    } else if (arg == "-anewer") {
+        if (args.is_empty())
+            fatal_error("-anewer: requires additional arguments");
+        return make<NewerCommand>(args.take_first(), NewerCommand::TimestampType::LastAccess);
+    } else if (arg == "-cnewer") {
+        if (args.is_empty())
+            fatal_error("-cnewer: requires additional arguments");
+        return make<NewerCommand>(args.take_first(), NewerCommand::TimestampType::Creation);
     } else if (arg == "-print") {
         g_have_seen_action_command = true;
         return make<PrintCommand>();