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Search - "array starts with 1"
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*Now that's what I call a Hacker*
MOTHER OF ALL AUTOMATIONS
This seems a long post. but you will definitely +1 the post after reading this.
xxx: OK, so, our build engineer has left for another company. The dude was literally living inside the terminal. You know, that type of a guy who loves Vim, creates diagrams in Dot and writes wiki-posts in Markdown... If something - anything - requires more than 90 seconds of his time, he writes a script to automate that.
xxx: So we're sitting here, looking through his, uhm, "legacy"
xxx: You're gonna love this
xxx: smack-my-bitch-up.sh - sends a text message "late at work" to his wife (apparently). Automatically picks reasons from an array of strings, randomly. Runs inside a cron-job. The job fires if there are active SSH-sessions on the server after 9pm with his login.
xxx: kumar-asshole.sh - scans the inbox for emails from "Kumar" (a DBA at our clients). Looks for keywords like "help", "trouble", "sorry" etc. If keywords are found - the script SSHes into the clients server and rolls back the staging database to the latest backup. Then sends a reply "no worries mate, be careful next time".
xxx: hangover.sh - another cron-job that is set to specific dates. Sends automated emails like "not feeling well/gonna work from home" etc. Adds a random "reason" from another predefined array of strings. Fires if there are no interactive sessions on the server at 8:45am.
xxx: (and the oscar goes to) fuckingcoffee.sh - this one waits exactly 17 seconds (!), then opens an SSH session to our coffee-machine (we had no frikin idea the coffee machine is on the network, runs linux and has SSHD up and running) and sends some weird gibberish to it. Looks binary. Turns out this thing starts brewing a mid-sized half-caf latte and waits another 24 (!) seconds before pouring it into a cup. The timing is exactly how long it takes to walk to the machine from the dudes desk.
xxx: holy sh*t I'm keeping those
Credit: http://bit.ly/1jcTuTT
The bash scripts weren't bogus, you can find his scripts on the this github URL:
https://github.com/narkoz/...52 -
I had to open the desktop app to write this because I could never write a rant this long on the app.
This will be a well-informed rebuttal to the "arrays start at 1 in Lua" complaint. If you have ever said or thought that, I guarantee you will learn a lot from this rant and probably enjoy it quite a bit as well.
Just a tiny bit of background information on me: I have a very intimate understanding of Lua and its c API. I have used this language for years and love it dearly.
[START RANT]
"arrays start at 1 in Lua" is factually incorrect because Lua does not have arrays. From their documentation, section 11.1 ("Arrays"), "We implement arrays in Lua simply by indexing tables with integers."
From chapter 2 of the Lua docs, we know there are only 8 types of data in Lua: nil, boolean, number, string, userdata, function, thread, and table
The only unfamiliar thing here might be userdata. "A userdatum offers a raw memory area with no predefined operations in Lua" (section 26.1). Essentially, it's for the API to interact with Lua scripts. The point is, this isn't a fancy term for array.
The misinformation comes from the table type. Let's first explore, at a low level, what an array is. An array, in programming, is a collection of data items all in a line in memory (The OS may not actually put them in a line, but they act as if they are). In most syntaxes, you access an array element similar to:
array[index]
Let's look at c, so we have some solid reference. "array" would be the name of the array, but what it really does is keep track of the starting location in memory of the array. Memory in computers acts like a number. In a very basic sense, the first sector of your RAM is memory location (referred to as an address) 0. "array" would be, for example, address 543745. This is where your data starts. Arrays can only be made up of one type, this is so that each element in that array is EXACTLY the same size. So, this is how indexing an array works. If you know where your array starts, and you know how large each element is, you can find the 6th element by starting at the start of they array and adding 6 times the size of the data in that array.
Tables are incredibly different. The elements of a table are NOT in a line in memory; they're all over the place depending on when you created them (and a lot of other things). Therefore, an array-style index is useless, because you cannot apply the above formula. In the case of a table, you need to perform a lookup: search through all of the elements in the table to find the right one. In Lua, you can do:
a = {1, 5, 9};
a["hello_world"] = "whatever";
a is a table with the length of 4 (the 4th element is "hello_world" with value "whatever"), but a[4] is nil because even though there are 4 items in the table, it looks for something "named" 4, not the 4th element of the table.
This is the difference between indexing and lookups. But you may say,
"Algo! If I do this:
a = {"first", "second", "third"};
print(a[1]);
...then "first" appears in my console!"
Yes, that's correct, in terms of computer science. Lua, because it is a nice language, makes keys in tables optional by automatically giving them an integer value key. This starts at 1. Why? Lets look at that formula for arrays again:
Given array "arr", size of data type "sz", and index "i", find the desired element ("el"):
el = arr + (sz * i)
This NEEDS to start at 0 and not 1 because otherwise, "sz" would always be added to the start address of the array and the first element would ALWAYS be skipped. But in tables, this is not the case, because tables do not have a defined data type size, and this formula is never used. This is why actual arrays are incredibly performant no matter the size, and the larger a table gets, the slower it is.
That felt good to get off my chest. Yes, Lua could start the auto-key at 0, but that might confuse people into thinking tables are arrays... well, I guess there's no avoiding that either way.13