date: Use ArgsParser and add ISO8601 / RFC3339 / RFC5322 output formats

Author: https://github.com/bcoles
Commit: https://github.com/SerenityOS/serenity/commit/fb9eb205446
Pull-request: https://github.com/SerenityOS/serenity/pull/4841

Base/usr/share/man/man1/date.md

@@ -0,0 +1,32 @@
+## Name
+
+date - print or set the system date and time
+
+## Synopsis
+
+```**sh
+$ date [--set date] [--unix] [--iso-8601] [--rfc-3339] [--rfc-5322]
+```
+
+## Description
+
+date is a utility to set the system date and time
+or print the system date and time in various formats.
+
+## Options
+
+* `-s`, `--set`: Set system date and time
+* `-u`, `--unix`: Print date as Unix timestamp
+* `-i`, `--iso-8601`: Print date in ISO 8601 format
+* `-r`, `--rfc-3339`: Print date in RFC 3339 format
+* `-R`, `--rfc-5322`: Print date in RFC 5322 format
+
+## Examples
+
+```sh
+# Print the current date and time in ISO 8601 format
+$ date --iso-8601
+
+# Set date to 1610017485 (UNIX time)
+$ date -s 1610017485
+```

Userland/date.cpp

@@ -26,6 +26,7 @@
 
 #include <AK/Optional.h>
 #include <AK/String.h>
+#include <LibCore/ArgsParser.h>
 #include <LibCore/DateTime.h>
 #include <stdio.h>
 #include <string.h>
@@ -38,26 +39,61 @@ int main(int argc, char** argv)
         return 1;
     }
 
-    time_t now = time(nullptr);
+    bool print_unix_date = false;
+    bool print_iso_8601 = false;
+    bool print_rfc_3339 = false;
+    bool print_rfc_5322 = false;
+    const char* set_date = nullptr;
+
+    Core::ArgsParser args_parser;
+    args_parser.add_option(set_date, "Set system date and time", "set", 's', "date");
+    args_parser.add_option(print_unix_date, "Print date as Unix timestamp", "unix", 'u');
+    args_parser.add_option(print_iso_8601, "Print date in ISO 8601 format", "iso-8601", 'i');
+    args_parser.add_option(print_rfc_3339, "Print date in RFC 3339 format", "rfc-3339", 'r');
+    args_parser.add_option(print_rfc_5322, "Print date in RFC 5322 format", "rfc-5322", 'R');
+    args_parser.parse(argc, argv);
+
+    if (set_date != nullptr) {
+        auto number = String(set_date).to_uint();
 
-    if (argc == 2 && !strcmp(argv[1], "-u")) {
-        printf("%lld\n", now);
-        return 0;
-    }
-    if (argc == 3 && !strcmp(argv[1], "-s")) {
-        auto number = StringView(argv[2]).to_uint();
         if (!number.has_value()) {
             fprintf(stderr, "date: Invalid timestamp value");
             return 1;
         }
+
         timespec ts = { number.value(), 0 };
         if (clock_settime(CLOCK_REALTIME, &ts) < 0) {
             perror("clock_settime");
             return 1;
         }
+
         return 0;
     }
 
-    printf("%s\n", Core::DateTime::from_timestamp(now).to_string().characters());
+    // FIXME: this should be improved and will need to be cleaned up
+    // when additional output formats and formatting is supported
+    if (print_unix_date && print_iso_8601 && print_rfc_3339 && print_rfc_5322) {
+        fprintf(stderr, "date: multiple output formats specified\n");
+        return 1;
+    }
+
+    time_t now = time(nullptr);
+    auto date = Core::DateTime::from_timestamp(now);
+
+    if (print_unix_date) {
+        printf("%lld\n", (long long)now);
         return 0;
+    } else if (print_iso_8601) {
+        printf("%s\n", date.to_string("%Y-%m-%dT%H:%M:%S-00:00").characters());
+        return 0;
+    } else if (print_rfc_5322) {
+        printf("%s\n", date.to_string("%a, %d %b %Y %H:%M:%S -0000").characters());
+        return 0;
+    } else if (print_rfc_3339) {
+        printf("%s\n", date.to_string("%Y-%m-%d %H:%M:%S-00:00").characters());
+        return 0;
+    } else {
+        printf("%s\n", date.to_string().characters());
+        return 0;
+    }
 }