Base: Add sysctl man page

Author: https://github.com/bcoles
Commit: https://github.com/SerenityOS/serenity/commit/69b98f7d326
Pull-request: https://github.com/SerenityOS/serenity/pull/5689
Reviewed-by: https://github.com/awesomekling
Reviewed-by: https://github.com/emanuele6

Base/usr/share/man/man8/sysctl.md

@@ -0,0 +1,50 @@
+## Name
+
+sysctl - configure kernel parameters at runtime
+
+## Synopsis
+
+```**sh
+# sysctl [-a] [variable[=value]]
+```
+
+## Description
+
+sysctl is a utility for managing kernel configuration parameters at runtime.
+This requires root privileges, and can crash your system.
+Available parameters are listed under /proc/sys/.
+
+## Options
+
+* `-a`: Display all kernel parameters and associated values
+
+## Arguments
+
+* `variable`: Retrieve the specified parameter
+* `variable=value`: Set the specified parameter to the specified value
+
+## Files
+
+* `/proc/sys` - source of kernel parameters
+
+## Examples
+
+View all parameters:
+
+```sh
+# sysctl -a
+```
+
+View `ubsan_is_deadly` parameter:
+
+```sh
+# sysctl ubsan_is_deadly
+ubsan_is_deadly = 1
+```
+
+Set `ubsan_is_deadly` parameter to zero (disabled):
+
+```sh
+# sysctl ubsan_is_deadly=0
+ubsan_is_deadly = 1 -> 0
+```

Userland/Utilities/sysctl.cpp

@@ -117,7 +117,7 @@ int main(int argc, char** argv)
     args_parser.set_general_help(
         "Show or modify system-internal values. This requires root, and can crash your system.");
     args_parser.add_option(show_all, "Show all variables", nullptr, 'a');
-    args_parser.add_positional_argument(var, "Command (var[=value])", "command", Core::ArgsParser::Required::No);
+    args_parser.add_positional_argument(var, "variable[=value]", "variable", Core::ArgsParser::Required::No);
     args_parser.parse(argc, argv);
 
     if (var == nullptr) {