The Art of Command Line

https://github.com/jlevy/the-art-of-command-line

by zalzal • 11 years ago

466 133 11 years ago

github.com

pella• 11 years ago

similar for data science: http://datascienceatthecommandline.com/

https://github.com/jeroenjanssens/data-science-at-the-comman...

michaelvkpdx• 11 years ago

I learned a dozen new things in the first 100 lines or so, that will save me hours, and I've been living in bash for 20 years.

Thanks for this!

cbd19847• 11 years ago

There's no reason to learn vi if you know Emacs. If you claim that Emacs isn't installed everywhere, guess what: Neither is vi.

If you want an "installed everywhere" editor, learn ed. If you're willing to take an editor with you (or otherwise make sure a specific editor is everywhere you are), there's no reason it has to be vi.

kec• 11 years ago

vi is a posix requirement, emacs is not. If the system you're working on has ed, it'll have some version of vi or vim as well.

shabble• 11 years ago

and not having to know ed is an excellent reason to learn vi :)

obCompulsoryEdJoke: https://www.gnu.org/fun/jokes/ed-msg.html

emidln• 11 years ago

I don't think this is true. I've certainly been in a bunch of hairy situations over the years where I had nothing fancier than ed available to me because I was in some sort of recovery mode. The single user mode that FreeBSD comes with is lacking vi if, for example, you don't have / mounted yet. Thankfully ed is in the ramdisk.

cbd19847• 11 years ago

Not in Ubuntu.

cogburnd02• 11 years ago

V7/x86 [1] has both vi and ed, but ed is easier to get to.

"Of course, we are not absolutely compelled to use ed, since V7/x86 comes with the full-screen editor vi (as well as the related line editor ex), but getting access to vi in this context would involve mounting the /usr filesystem and changing various environment variables and settings to allow editing in full-screen mode. Some basic ed skills are particularly useful in the V7 world, and most of all when one is involved on system administration tasks." [2]

[1] http://www.nordier.com/v7x86/

[2] http://www.nordier.com/v7x86/doc/v7x86intro.pdf

umanwizard2• 11 years ago

I can't remember ever encountered a unix-like system without "vi" installed. I've used (and set up) machines running FreeBSD, DragonflyBSD, OSX, Ubuntu, Debian, RHEL, ...

Plenty of those didn't have emacs, especially on first boot, when you're most likely to need to modify network configuration files in order to get online to install new packages in the first place...

Edit: By "vi" I mean that somewhere in the path there is a program called vi. Of course, usually this is nvi, vim, evil, etc; I don't mean the original UNIX vi binary.

cbd19847• 11 years ago

I can't remember ever encountered a unix-like system without "vi" installed.

Default Ubuntu install.

dagw2• 11 years ago

I can't remember ever encountered a unix-like system without "vi" installed.

It's often/always part of a full install, but it isn't always there when you end up in rescue mode and/or situations where /usr won't mount.

hobarrera5• 11 years ago

Not on OpenBSD on rescue mode, or when booting from bsd.rd. Pretty sure the same applies to several others.

However, ed is available, and vi is closer to ed than emacs is. And emacs won't be available either.

baby2• 11 years ago

I much prefer emacs and at least emacs shortcuts are by default in most shell (and everywhere in osx!) but no, every servers I install (debian, ubuntu, osx...) comes with vi but not emacs.

cbd19847• 11 years ago

Anyone considering using vi should be warned away by this practice of "disagreement by downvoting". If they do it here, imagine what they would do to a bug report!

scrollaway6• 11 years ago

To disable slow i18n routines and use traditional byte-based sort order, use export LC_ALL=C (in fact, consider putting this in your ~/.bashrc).

Do not. Having a non-utf8 locale means you won't be able to handle utf-8 sanely ("that's why it's faster") and it will break at the most inexplicable times. Any non-latin1 character appearing in your prompt or command line with this will mess its spacing up for example. Do not do not do not.

Hell I even check for it in my .zshrc: https://github.com/jleclanche/dotfiles/blob/master/.zshrc#L3...

Good post otherwise.

binarycrusader3• 11 years ago

I have to reiterate this; don't do it -- sort order changes and you'll run into other mysterious issues.

It's not worth the "performance improvement".

cle• 11 years ago

In some cases, it certainly is worth the improvement. Performance improvements translate into $$$.

Knowing that "LC_ALL=C can improve performance but cause UTF problems" is awesome information to base a design on. A blanket statement like "never use LC_ALL=C" is not.

unhammer5• 11 years ago

There are good reasons to use LC_ALL=C for certain commands, especially if you want sorting that's stable across different systems. Sometimes you want "aa" to be before "b" even though the Norwegian UTF-8 locale puts it after "å" (which comes after "…zæø"):

    $ echo $'a\naa\nb\nå'| LC_ALL=C sort 
    a
    aa
    b
    å
    $ echo $'a\naa\nb\nå'| LC_ALL=nn_NO.UTF-8 sort 
    a
    b
    å
    aa

Even worse, some characters that are byte-different collate the same:

    $ echo  $'∨\n∧'|LC_ALL=C sort -u
    ∧
    ∨
    $ echo  $'∨\n∧'|sort -u
    ∨

Handling Unicode sanely requires understanding some Unicode.

thristian• 11 years ago

Some environments support a locale named "C.UTF-8" - with the same familiar sorting and formatting rules as the C locale, but with proper UTF-8 support.

zalzal2• 11 years ago

Using C locale is useful when processing very large data files in a shell, e.g. on a server. For example, uniquing or set difference will work many times faster (and doesn't require the slow/fancy collation calculations). But yes, it's a good point, of course it shouldn't be used on your desktop globally or apps will break. I'll clarify that.

cmrx642• 11 years ago

Setting LC_COLLATE=C and leaving the rest to a proper locale can often win you what you want without losing much.

stass3• 11 years ago

The question is, do you need to handle UTF-8? In most cases of sever management having LATIN1 would suffice, or appropriate localized 8-byte encoding.

You can apply the same argument to any other obscure encoding scheme, not just UTF-8. The answer is really to pick the encoding which will suite the most usecases and won't be painful to use.

gchpaco2• 11 years ago

How is ASCII or Latin-1 somehow not an obscure encoding scheme by your parlance? Latin-1 is less common by quite a bit on the web than UTF-8, and ASCII might be if UTF-8 wasn't a superset.

Fact of the matter is people have to get out of the habit of going "oh, that will never be relevant for me", because a) that's unlikely to be true for everybody (for example in a server environment you can't even write perfectly good North American names like Étienne let alone perfectly good older-than-the-country names like Þórr) b) it's unlikely to be true even for you as you will discover the first time you try to read a file written by somebody else c) it promotes intellectual laziness that makes later internationalization efforts difficult to impossible, because they're trying to convince people like you to care about stuff they find inconvenient but that is of vital importance to your customers.

I know of a man whose first name is Þórr who outright refuses to deal with any organization that will not let him write his name, and I have a hard time disagreeing with him.

xenophonf3• 11 years ago

I have the following set in my .cshrc:

  setenv LC_ALL en_US.UTF-8
  setenv LC_COLLATE C             # use the ASCII sort order

What have I broken, and how badly?

scrollaway6• 11 years ago

You're not breaking anything on a technical level with that. Be wary of anything that deals with string or character comparison however (including regexes).

lejoko• 11 years ago

This won't work because LC_ALL overrides LC_COLLATE (and all the LC_* variables actually). It's LANG that you want to use. LANG is overriden by LC_* which are in turn overriden by LC_ALL. Don't use LC_ALL in your config files, use it only for one shot command lines or in scripts that need to be sure of the environment they run in.

voltagex_2• 11 years ago

Raised https://github.com/jlevy/the-art-of-command-line/issues/22

scrollaway6• 11 years ago

Thanks! Didn't think of filing it as an issue.

zalzal2• 11 years ago

The discussion here has tended to focus on either one or the other of two different facts:

You absolutely need to be aware of and manage language and locale settings diligently. This is a big topic, but generally, whenever possible, use UTF8. And you generally don't want to change your desktop OS or applications' locale or language settings other than that.

However, if you are processing data files and are aware of the implications, and can get away with treating data as binary instead of character streams -- for example, any of the command sequences that use sort/uniq for uniqueness or set union/intersection/difference -- then using C locale is way faster. As in, the difference between doing something in an hour on a big machine and rewriting a whole pipeline in Hadoop. A good fact to know.

It's obvious I (the author) didn't make the simultaneous truth of both these points clear. I'll rewrite.

agumonkey• 11 years ago

Just throwing this http://mywiki.wooledge.org/BashGuide (it's listed 2 indirections deep so will probably be missed)

Every time you have an issue with the shell, go there.

MachinaX2• 11 years ago

The Linux Command Line (free pdf): http://linuxcommand.org/tlcl.php

tomaac• 11 years ago

Hosted on Sourceforge which is now blocked almost everywhere.

MachinaX2• 11 years ago

You're exactly right tomaac. Thank you for your comment.

The reason: http://arstechnica.com/information-technology/2015/05/source...

hamburglar• 11 years ago

The author should prepare to catch some hell for advocating 'ForwardAgent=yes' in ssh configs.

xenophonf3• 11 years ago

I had meant to take another look at ProxyCommand (http://heipei.github.io/2015/02/26/SSH-Agent-Forwarding-cons...), so thanks for the reminder!

widdershins• 11 years ago

Seems like a good introduction. I'm an amateur who's been using IDEs up until now. I'm just starting to become dimly aware of the power at the command line, and slowly learning in a haphazard way. This could be very helpful.

jwcrux• 11 years ago

Fluency on the command line is a skill that is in some ways archaic...

I don't see this to be the case at all. Plus, having this be the opening line may cause people to equate archaic=I don't need this.

I'd suggest (would pull request but afk) that you remove "is a skill that is in some ways archaic".

_jal• 11 years ago

Agree. I've been hearing people saying the command line is archaic since Windows 95, and probably before that. Yet somehow I (any everyone I work with, and have worked with over the past 25 years) still works in a shell daily. I don't understand how someone on the technical end of running large internet services could avoid it.

Sure, GUI tools have crept in here and there. And I understand that some toolchains mandate all-singing, all-dancing IDEs. I don't work in those areas (the closest I've come was doing Java work for about five years and I still lived in vi, because Eclipse makes me homicidal). And I still see our iOS developers using `find' and `sed'.

Which isn't to say GUIs can't improve on the command line for some things. For example, the MacOS tool "A Better Finder Rename" (despite its inability to rename itself something less clunky) is a great tool for mass-renaming, e.g., photos. I have written such critters before as shell/perl/python scripts, but pulling EXIF data and renaming files programmatically is ticky and potentially destructive enough that I tend to write it once and then not modify it unless it breaks. The GUI preview and regex capture display makes this much less annoying.

Nemcue• 11 years ago

It's a fun experience trying to introduce command lines to people who have lived in IDE-land all their lives.

"Command Line?! HAHAHAH"

lloyd-christmas• 11 years ago

Comparing your first sentence and that of the author, you're missing what I see as the key word: "skill". I use command line everyday. Probably most developers do as well. But I definitely don't have "skill" in it. I think the point is that most developers can get by with nothing more than the basics (whatever "basics" are in the context of their work). The command line isn't archaic, but command line as a fluency might be.

mbillie12• 11 years ago

https://github.com/jlevy/the-art-of-command-line/pull/12

bdamm• 11 years ago

If you learn bash, and you learn vi, then the next most glorious addition is:

set -o vi

Then you have vi keys in your shell. And it is marvelous.

jonahx• 11 years ago

Learning about this was a revelation for me. I can't live without it now.

javajosh• 11 years ago

Can you share a little more info about this? I tried it but found it rather confusing.

Also, for more readline maneuvers: http://unix.stackexchange.com/questions/21788/how-to-delete-...

brown-dragon• 11 years ago

`set -o vi` allows us to use `vi` bindings instead of the default `emacs` bindings.

The way to think about it is that the prompt starts out in `vi insert mode` so whatever we type in will just be inserted at the prompt. However, we can hit the`Escape` key and move into `vi normal mode` where the keys are interpreted as normal `vi` commands. So, for example, once we hit `esc` we can navigate around the line using `h` and `l` and navigate history (previous lines) using `k` and `j`.

Commands I find very useful are:

`jk` : for history navigation

`bw`: for moving in the current line. These are word movement commands that are faster to navigate with.

`cw` : similarly, changing a particular word in the current line is also great. This works particularly well with history - retrieve a previous command and change a word or option

`dw` : for deleting the current word

`/` : is a fantastic command for searching history. `/cd` will bring up our last change directory command and just hitting `n` will cycle through all our change directory commands that are in history.

`AI` : to insert at the beginning/end of line

...and so on. If you have `vi` muscle memory it's a fantastic option for working on the shell.

(edit: Formatting)

barbs• 11 years ago

Agreed. I made a pull-request for this.

https://github.com/jlevy/the-art-of-command-line/pull/9

a3n• 11 years ago

That's nice, but it only affects the command line.

Instead of that, create the following file:

~/.inputrc (tilde slash dot-inputrc)

And in that file put at least this:

set editing-mode vi

Now every program that you run that a) has its own command line, and b) uses the readline library (there are a lot) has vi commandline editing. psql, mysql, telnet, lftp, and many more.

man bash has a section on READLINE. For example, in man bash search for

editing-mode

baby2• 11 years ago

or if you learn emacs you have emacs shortcuts by default in shells.

which goes against his childish comment on emacs:

Learn Vim (vi). There's really no competition for random Linux editing (even if you use Emacs, a big IDE, or a modern hipster editor most of the time).

carlisle_• 11 years ago

I would argue it's not childish and is a strong point considering emacs is not typically installed by default. Vim isn't usually installed by default either, gotta go with good ol' vi, unless your distro maintainers are nice and symlink vim to vi for you until you install vim.

erikb• 11 years ago

At first I thought the same as you, but then I realised that he's not talking about your average editor, but about which editor to use if you SSH into a random web server etc. The thing you use in a foreign environment. That's what "random Linux editing" probably means.

barely_stubbell• 11 years ago

I'm glad the author took time to mention sl - every sysadmin should make sure that its installed on all the boxes they manage.

pyre• 11 years ago

Good ole' steam locomotive command...

craneca0• 11 years ago

The new csysdig curses CLI [1] unifies and replaces a bunch of the system debugging tools listed here.

[1] https://github.com/draios/sysdig/wiki/Csysdig%20Overview

Wonnk13• 11 years ago

pretty good writeup. Learning nohup was a life changing experience for me.

unhammer5• 11 years ago

there's also disown. It's a bash builtin, so you'll have to type "help disown" ("man disown" gets you nothing). E.g. to run touchegg and close your terminal, keeping touchegg running:

   touchegg & disown; exit

scrollaway6• 11 years ago

I use an alias for it:

    function launch {
    	type $1 >/dev/null || { print "$1 not found" && return 1 }
    	$@ &>/dev/null &|
    }
    alias launch="launch "

karmicthreat• 11 years ago

So this is tangentially related by why do people seem to push Vi? Nano is a perfectly serviceable editor. If I need to do extensive editing I always end up loading it into Atom, Sublime or some other editor anyway.

I've never really had to use a console editor for more than 10s of lines.

elchief• 11 years ago

nano is super easy to use, I agree. I tried vim and gave up. Will try again.

baghira• 11 years ago

I find it a bit irksome that when discussing command line editors, the dichotomy appears to be be "nano vs vim".

There are other CLI editors. I'm quite partial to ne (the Nice Editor), which has more manageable shortcuts than emacs, a command line (it's still a non-modal editor, to be clear), macros and syntax highlighting. Also jed is not bad. While vim (and nvim) have advantages, and certainly benefit from being ubiquitous and having ther shortcuts replicated in other programs, users should shop around, even on the command line.

mbillie12• 11 years ago

vi keybindings are ubiquitous, so familiarity with the editor is beneficial outside the editor. Just offhand, both ncdu and tig (which I have used in the past hour) respond to vi keystrokes.

It's not as hard as it first seems to learn, either. Well worth the time spent, vi is worlds more powerful than nano.

kjs3• 11 years ago

"I don't understand why everyone doesn't do things exactly like I do using only tools I like" is a really stupid way to look at the world.

teirce• 11 years ago

Ironically, it's unclear whether you're countering the comment's argument, or the article's argument.

"Use vi, nothing beats it." == "I use x and I like it just fine."

If that was your intention, my mistake. It's just not apparent.

girvo• 11 years ago

Nano is fine for 10s of lines, but Vim is great for much much more than that. It's also nice to have the same keybindings for every console app (gosh I love readline), and it's repeat commands make editing text an absolute breeze. Why open another editor on my host if I can edit the file in my console on a remote server?

AdieuToLogic6• 11 years ago

In modern Bourne shell derivatives (Bash, ksh, some POSIX shells), the command:

set -o emacs

Will give command line editing bindings compatible with Emacs (which is also the default editing keys in MS-Windows and many IDE's BTW).

HTH

greggyb• 11 years ago

Emacs bindings are not at all compatible with MS Windows.

taco_emoji• 11 years ago

Nano is not as ubiquitous as vi. Every single *nix box will have vi on it, so even if you prefer something else, it's still in your best interest to learn the basics of vi.

hobarrera5• 11 years ago

If I need to do extensive editing I always end up loading it into Atom, Sublime or some other editor anyway.

So you're saying "why would you use X, when you could avoid that by using Y"?

Well, because people prefer X, for a variety of reasons. Not to mention vi is installed everywhere, while sublime and atom are not.

cmrx642• 11 years ago

StrictHostKeyChecking=no

And welcome to MITM haven. This is awful advice if you care about the first S in SSH.

Karunamon• 11 years ago

Depends on your circumstances, really. If you're in an environment with lots of VM's floating around, being created, destroyed, and so on, dealing with SSH's paranoia (why can't I just dismiss a warning about a host/key mismatch instead of having to edit .known_hosts?) quickly becomes an exercise in frustration for dubious security benefit. (If the enemy is on your LAN and able to manipulate your DNS, you've already lost)

On your home box, sure. But let's not pretend there's not a reason for the option to exist.

richardwhiuk• 11 years ago

In which case, just use telnet. Seriously.

DDub• 11 years ago

I use an alias to select when to, and not to, use host keys;

alias ssht='ssh -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no'

ssht floaty.vm # does not use host key checking

ssh my.bastion.host # validates host key

Really I ought to get SSHFP records populated when my vm's are created...

jamespo• 11 years ago

In these environments you can use server certificates

https://www.digitalocean.com/community/tutorials/how-to-crea...

AYBABTME• 11 years ago

What would be good is an interactive confirmation when a host fingerprint has changed, instead of a flatout abortion and having to edit your `known_host` file. I have to SSH into hundreds/thousands of VM that reuse the same IPs/FQDN sometimes, and the strict host checking is a major PITA. I haven't turned it off tho, I prefer the pain to MITM.

voltagex_2• 11 years ago

I wonder if SSHFP records on Avahi/mDNS would work?

xorcist• 11 years ago

Don't use SSH in a trust-on-first-use configuration in that situation.

There are two other modes to use. Either DNSSEC with SSHFP fingerprints, or sign your host keys with a CA key that you install on all your machines.

A decent configuration management tool could also keep known_hosts up to date, but it tends not to be worth the trouble. Do the above first.

ryenus2• 11 years ago

  cat hosts | xargs -I{} ssh root@{} hostname

glad to know this one :-)

  echo y | xargs -Ix echo x

how tricky!

jnpatel• 11 years ago

I agree, this is one of my favorite tricks. I like to think of xargs as a `map` function over stdin lines.

As the article mentions, especially useful when combined with the -P flag for paralellism.

    cat urlpaths.txt | xargs -I{} -P wget domain.com/{}

Another handy trick, is to use `sh -c` or `bash -c` to include multiple commands with xargs.

    cat dirs.txt | xargs -I{} sh -c 'cd {}; touch file;'

cbd19847• 11 years ago

There's no reason to learn vi.

cbd19847• 11 years ago

Anyone considering using vi should be warned away by this practice of "disagreement by downvoting". If they do it here, imagine what they would do to a bug report!

webnrrd2k• 11 years ago

If you're into the command line, I'd recommend getting a physical copy of Unix Power Tools [1] and spending some time with it. This is a nice article, but Unix Power Tools is better in almost every way for learning the basics (and more) of the Unix command line. This article mentions a few more modern tools, but Unix Power Tools has a far better explanation of what's going on.

[1] http://www.amazon.com/Unix-Power-Tools-Third-Edition/dp/0596...

mediocrejoker• 11 years ago

To locate a file by name in the current directory, find -iname something . (or similar). To find a file anywhere by name, use locate something (but bear in mind updatedb my not have indexed recently created files).

I think this will glob unless you escape the asterisks. Also on my system (debian 8) I need to put the directory to search first, or not at all:

find . -iname \something\

find -iname \something\

edit: hackernews ate all my asterisks

myth_buster• 11 years ago

  edit: hackernews ate all my asterisks

Well that solved the mystery.

AdieuToLogic6• 11 years ago

I think this will glob unless you escape the asterisks.

The majority of times, this is the case. At least one exception is when the shell pattern does not match one or more files in the directory which find(1) is executed. However, this can be "surprising" so it's best practice to either use escapes or ensure interpolation is disabled via single quotes (in Bourne shell syntax).

Also on my system (debian 8) I need to put the directory to search first...

FWIW, you can specify more than one directory if desired. The primaries will be applied to the results of each.

wnoise• 11 years ago

The majority of times, this is the case. At least one exception is when the shell pattern does not match one or more files in the directory

Thankfully zsh has the NULLGLOB option which will do the right thing and expand to an empty list, of the zero matching files.

hobarrera5• 11 years ago

This depends a lot on the terminal, and my advise is to always suround the glob with quotes:

    find . -iname "*file*"

zsh will cry that nothing matches the glob if you don't. bash will expand it if something matches, or pass it as-is to the client if something does - which will give you unexpected results.

mozumder• 11 years ago

Man so I guess tcsh/csh lost the shell wars?

AdieuToLogic6• 11 years ago

Nah, just the hearts and minds.

seri• 11 years ago

Unix tools are very powerful, but they are not as intuitive as I would like. It would be nice if we can have an httpie for process management, one for text manipulation, another for system stats, and so on.

AdieuToLogic6• 11 years ago

Powerful tools are rarely instinctive. Quite often, one person's obvious is another's opaque.

MarcScott• 11 years ago

I'd never even thought about commenting a line I was half way through writing, when suddenly realising I'd forgotten the correct arguments.

I normally end up opening another terminal and using man there.

unhammer5• 11 years ago

I do this sometimes when I want to run some command first from earlier in my history, then the commented out command also stays in history so I can continue with it after I've re-run the earlier command first.

AdieuToLogic6• 11 years ago

Much, much more can be found at:

http://www.commandlinefu.com/commands/browse

Ardebou• 11 years ago

Before that I was not so familiar with cmd. After that I was.

stinos• 11 years ago

Fluency on the command line is a skill now often neglected or considered archaic

By whom? (honest question: even the most GUI oriented people I know reckon the power of command line skills)

weavie• 11 years ago

I work in a .Net house. When we had to move to front end development which required using grunt shock from the command line there was plenty of dissent at how we were being forced back into the "dark ages".

natch3• 11 years ago

Another one for obscure but useful: jot

# print 10 values from 1 to 10, with leading zeros:

for n in `jot -w "%04d" 10 1 10`; do echo $n; done

anc842• 11 years ago

Just use Bash's builtin things:

for n in {0001..0010}; do echo ${n}; done

willthames• 11 years ago

Or seq -f %04g 1 10

stiGGG• 11 years ago

Nice, but this needs an actual version of bash, with that oldie shipped with OSX Yosemite the result is not padded with zeros.

natch3• 11 years ago

Cool, thanks.

joelthelion• 11 years ago

No mention of autojump? :-p

ryenus2• 11 years ago

I googled about autojump, then found fasd and decided to go with it.

https://github.com/clvv/fasd

gitaarik• 11 years ago

One really useful shortcut I learned in bash is Ctrl-/ which is a sort of undo for bash when composing a command. Can't really explain how it works, you should try it out yourself.

Also really handy is Ctrl-Y, which pastes the last cut characters by Ctrl-W, Ctrl-U or Ctrl-K.

nanny• 11 years ago

C-/ and C-y are from readline which mimicked them (and many more) from Emacs.

hobarrera5• 11 years ago

Fun fact: alt+# is impossible on a Spanish keyboard, because alt+3 = #. So you actually need to hold alt to type the character in the first place.

The Art of Command Line

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