YSK about [Unix tools]

This Slack discussion, featuring myself in some sleep-deprived rambling, occurred in hackernoon's official #protips channel, and has been [barely] edited for readability. YSK about , short for “list open files”. since everything, literally everything from network sockets to camera handles, is a file in unix-based systems (like macos). this means you can do things like in the terminal, to see if anyone’s using your camera (even if the little light is off) or you can do to see all programs with open network ports, if you want to say, kill a webserver that ran away on you, to open up the port. or if you’re locking down a machine. the thing’s a power tool austin Oct 14, 2020, 2:30 PM lsof lsof | grep "AppleCamera" lsof -i -P -n | grep LISTEN or ! talk about power tools. that thing will send literally anything over anything. want to test an old PPP connection? send a “malicious” packet to test your webserver’s mettle? see what happens when you send a UDP formatted packet over TCP? . more unix tools incoming, in this thread austin Oct 14, 2020, 2:33 PM netcat netcat how about ? it’s basically wireshark before wireshark was cool — if you’re on an ssh connection in particular, might be worth brushing up on (i know, wireshark can work over an ssh connection, but imagine you’re on a desert island. with a computer.) point is, these old school tools can be useful sometimes too (and can be piped together like any ol’ unix tool) austin Oct 14, 2020, 2:35 PM tcpdump tcpdump ok so it’s decided: this is a thread about useful unix tools. please don’t post in here, people — i’m going to turn this into a post later austin Oct 14, 2020, 2:36 PM is a good one too. (i’m just thinking these up off the top of my head, so if i seem all over the place, it’s because i am). the tool will keep a program running even if your ssh connection fails! talk about useful austin Oct 14, 2020, 2:37 PM screen screen oh! / ! those things are amazing. you can basically poke around inside a running program. think of it like game genie for your code austin Oct 14, 2020, 2:39 PM strace ptrace . one of the most underrated tools on unix…you can test an whole ass webserver with . i mean, there are a thousand tools for “REST testing” these days, but is the og. austin Oct 14, 2020, 2:40 PM curl curl curl , again underrated and used to death. especially powerful with unix pipes. i mean, you can combine grep with literally any other tool in this list, except maybe and only because that wouldn’t really make sense…unless you’re grepping redirected output? idk. point is, all these tools can talk to each other using a standard format, one we all know: text! austin Oct 14, 2020, 2:42 PM grep screen btw, at this point, it’s worth mentioning: half the cool unix tricks i’ve learned, i learned from aka , creator of . check it! she knows more about unix and linux systems than i can probably ever hope to, and she presents it in a really fun, digestible format. austin Oct 14, 2020, 2:44 PM https://twitter.com/b0rk https://jvns.ca/ http://wizardzines.com let’s see… is actually more powerful than most people realize. you can set up “chains” of ssh connections, you can set up all sorts of crazy network configs….i mean, it does more than just remote terminal logins. austin Oct 14, 2020, 2:46 PM ssh fun fact: (and too, i believe) have an interface for editing remote files on your local instance! so no more using default to edit files over ssh! 😄 austin Oct 14, 2020, 2:47 PM emacs vim vi ! i forgot about , because everyone does. basically, if you have data that’s spit out in a columnar format like , or , or [insert any unix tool on the planet], you can use a simple command to pull a single value out of a given column, and so much more. which i don’t know off the top of my head because the columnar data processing is all i’ve really needed. but in a pinch, you can even use it like austin Oct 14, 2020, 2:50 PM awk awk ps lsof awk grep …here be dragons, folks. short for “stream editor”, sed is like find and replace on some super steroid derived from the blood of all the disgraced baseball players in the 90s. anyway, sed can do stuff like find and replace every single instance of a regex match with another string or pattern (including regex capture groups!), in place. meaning it will edit your files with no recovery plan, no backup. that’s why i say: here be dragons. this is a power tool so powerful, you can cut a limb off. be careful. austin Oct 14, 2020, 2:53 PM sed is useful, but damned if i remember how to use it. there’s even . i mean you can create the unix equivalent of zip files, and decompress them as well. it’s useful, i just…i need google to use it. austin Oct 14, 2020, 2:54 PM tar https://xkcd.com/1168/ is a good one. i mean, if you ever need to find something and don’t have the luxury of macos’s finder features, this is your tool. it can find files with a pattern, using modification time, and so much more. combine with a unix pipe and for extra fun! austin Oct 14, 2020, 2:56 PM find xargs , that’s useful as well. basically it’s the unix equivalent of the “spread operator” in JS, if that makes sense. austin Oct 14, 2020, 2:56 PM xargs two more: the first, , is essential for any unix or linux user. it’s quite simply, the manual pages. use it as a system reference, for remembering what a given flag does, or whenever doesn’t cut it austin Oct 14, 2020, 2:59 PM man $TOOLNAME --help the last is — literally. this will, given a keyword, tell you which tools are appropriate for your use case! like if you type , it’ll tell you about file-related tools. it’s like the index they used before search engines sort of drove it into the shadows austin Oct 14, 2020, 3:00 PM apropos apropos file hope you enjoyed this sleep deprived rant! back to my regularly scheduled programming… austin Oct 14, 2020, 3:01 PM