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Comment by smith-kyle | Hacker News Reader

> Learn basic Bash. Actually, type man bash and at least skim the whole thing; it's pretty easy to follow and not that long

Skimming The Grapes of Wrath would be shorter. Thank you, but no thank you.

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If you read, execute and understand all the code in "The Advanced Bash Scripting Guide", you will suddenly find yourself in the top 10% of people who use bash.

https://www.tldp.org/LDP/abs/html/

(as a pdf: http://tldp.org/LDP/abs/abs-guide.pdf )

I'm pretty sure if you read, execute and understand all the code in most advanced guides to a language you will suddenly find yourself in the top 10% of the users of that language. But the understand is the hard part.

Wonder why they advise cat /dev/null > file to empty a file rather than echo > file

Because echo-ing into a file will make a file with 1 byte in it: a single newline character.

echo -n >file

Well, `echo > file` won't empty the file, it will have a newline in it. At the very least you'll need `echo -n > file`.

Trick: You can use just

    >file

I've always done it as: `> file`

That's actually very nice, I never thought about that one.

Unfortunately, this doesn't work in fish:

> fish: Expected a command, but instead found a redirection

Right but I don't think anyone is really concerned if it runs in fish. Fish is non standard and doesn't try to adhere to bash. If we want to write fish shell scripts we can do that elsewhere

Funny how the same sentence applies to bash wrt POSIX shell in other contexts

Or after thinking about it for a moment, true > file. Or by its shorter name, :> file.

`printf > file`, but there's endless ways of achieving the same thing (and that's part of the beauty).

or why not `touch file`?

That works to create an empty file if none exists, but if the file already exists then 'touch' simply updates its atime/mtime and doesn't alter the contents. This latter effect is actually the purpose of touch; the file creation part is just a side effect.

IMO, the most natural method is simply:

    >file

This will empty a file without closing or invalidating any open file handlers so you can empty things like log files without restarting the services that are populating those files.

Or why they aren't recommending 'truncate -s 0 file'

The Bash Hackers Wiki is a much better resource, especially as reference material: https://wiki.bash-hackers.org/

How large is it? Like 40p when you put it on a printer?

Let me help you with this:

    man -t bash > man.ps && lpr man.ps

Then, grab a coffee, sit in the sun and spent some quality time with your tools. :)

The man pages are the worst form of information ever for anybody trying to really solve any real-life problem which is not specified as "learn all unnecessary switches and once-useful but used-by-nobody-today options of a command X."

It happened to me often enough that even when I knew what I wanted to achieve and which command X could do that I would first try to read darned man page and fail to find the solution, but then just googling gave enough of material to

a) have something to try

b) have a discussion of the cases where that "something" doesn't fulfill the use most use cases of those who asked (the "natural need") including, of course, the use case I've had.

I have a completely opposite attitude. Bash is horrible on many levels. Bash man page is only a part of horribleness.

The main problem for all man pages is that they are mostly as if written for those who already know about every unnecessary detail of both the tool in question and all related tools or environmental issues, but who searches for some even more obscure detail among all obscure details that they already know.

Not to mention the descriptions that aren't: e.g. the complete explanation of the option --frob-blonk FILE would be something like "this option uses the FILE as the frob blonk" oh, how helpful.

I use bash every day, but I've at least managed to reduce its use to the minimum that keeps me still sane.

Skimming the bash manpage every once in a while is important to stay out of information bubbles.

There are too many developers who rely only on Google/Stack Overflow to find and write answers to questions, and it's common to repeat bad, incomplete, or outdated information. I can think of a lot of times when the most accepted SO answer for many questions was "copy and paste this gigantic block of code" instead of using an existing command.

Most of information there is not worth having in my "brain cache" at all, and especially not worth refreshing it regularly. Life is too short to even trying to remember the things like what's the difference between .bash_profile .profile .bashrc .inputrc and .bash_login (bonus point for remembering what is redirected to what in the files themselves in which distribution) or what the hell is a "login shell" and what is not. And there are many such details that are effectively useless for 99.99% of the users but they just have to survive the suffering to fix the darn thing when they have some issue.

I'm sure even most of the readers here can't give a one line answer what is the "right" and "general" way to preset a darn variable for a shell. By design of all these artifacts we work with, it necessarily leads to a page-length discussion of which shells exist and what their differences are and whatnot. Such a waste of everybody's mental energy on a global level.

I think it's a bit unfair you're being downvoted because you raise some good points. A lot of people agree POSIX is a mess and you've highlighted a fraction of reasons related to that. Would any of the downvoters care to elucidate? Maybe I'm missing something obvious.

Not a downvoter, but I assume the reason is that many people do understand these mechanisms without evicting too much from their brain cache.

Files like .bash_profile, .bash_login, .profile, .zprofile, /etc/profile, /etc/profile.d/whatever.sh all serve the same purpose, the primary aspect of which is to apply things like environment variables at login. Display managers and [login] shells source these things in a predictable precedence order so that environment variables are correctly inherited by children of GUI environment processes and login shells.

Login shells? Well yeah, the point of a login shell is that it invokes login-related tasks like setting environment variables from a profile. That's intentionally separate from the behavior of interactive shells because the environments of interactive shells may have been modified intentionally and shouldn't be "reset" to the values applied at login.

edit: also .inputrc is the readline configuration file for things like shortcut keys in all programs which use readline (not just bash) and .bashrc is for customizations specific to interactive shells

You see I’ve read this kind of information in exactly the words you use more than once and I still can’t summarize in one sentence where should one put his variables for things to “just work.” Locally for one user. Provided I just don’t know and don’t even care what the differences between the login and interactive shells are and that I just run the whatever terminal it is default from the GUI menu (whichever GUI it is).

And your explanation what the differences are is for me still circular, exactly like in the man pages: login shell is the one which invokes login-related tasks, and I should care about the difference from the interactive shells. I still have no idea what that even means, it is what exactly happens when?

Anybody knows some sane explanation of these? I admit I never tried to find it, as I tried to read the man pages, didn't find anything reasonable, but knew that it doesn't matter to me. I just want the darn variables to exists whenever I need them. I don't care about the differences. One single place is enough.

But now that you say that you "do understand these mechanisms without evicting too much from" your "brain cache" I'd really like to learn everything about the differences. Specifically, when is one invoked and when another for the user "acqq", let's say, on a default Ubuntu system, and on a default Red Hat system?

Are really more different user shells invoked in different forms for a single user, on a single machine, between the booting of the machine, logging in (in GUI) and then starting a few times the terminal with shell inside? When is invoked and which is invoked when? And why shouldn't be a single place for the variables I want to define? No idea, but I would be grateful to read about it now. Thanks in advance.

The general way to set an environment variable is in /etc/profile or ~/.{bash_,,z}profile.

PAM uses /etc/environment, and systemd would prefer to have you set up default environment variables in /etc/systemd/system.conf. You can even pass them directly to Linux from your bootloader (unrecognized arguments on the kernel command line in the form foo=bar become environment variables), but the profiles are the generally accepted way of doing it.

It is a joke? If I want to set some variable to be present for a single user (me) I surely don't want to ever touch /etc/profile or /etc/systemd/system.conf (and I have no idea what /etc/environment is supposed to be). And even less want to change something in a bootloader. The things are surely configurable in my user home directory.

I see where you're coming from, but I think it's the attitude of the developer that's more important. I've learned a good deal of Bash from places like SO, but I've always tried to learn why the command is like that, and I've found other sources more useful than man. If someone is the kind of developer who blindly copies and pastes chunks of code from SO then there are bigger problems than not using man.

I'd agree with this. I can't stand prolix documentation when I'm just trying to get something done (I'll never understand why people extol the Python docs!). I used bropages [0] for a while but it isn't as expansive as it should be, presumably on account of a lack of traffic.

I'm happy to read more expansive pages in my own time but when I'm 'in the zone' as it were, the last thing I want to do is read through why something works. Perhaps it's a gap in the market? Or more likely I'm in the minority!

The Python docs are, on the contrary, quite good when compared to the GNU man pages. There is an advantage of the context: the GNU *nix tools have to reflect how the things grew, totally independently, accidentaly and ad-hoc. Python is much narrower topic and the development mostly had some concept of the "overall goal."

The Python docs opened the door to programming as a career for me in my late 20s. I/O, concurrency, polymorphism, it's all there. Thanks Python.

Sometimes I just want to reach through the monitor and smack the nerd that ends every answer on a forum or SO with, "you just type awk -@dee(++ | grep %%s, man pages are your friend. "

When you don't know what to look for, it is not as simple as "looking something up".

The worst are these who don’t answer the question at all but “helpfully”’give you the link to the man page. If the answer contains an example which matches the question it is useful.

(And I too actually consider awk much simpler than e.g. bash)

TLDR is a pretty cool project that cuts out the verbosity of man pages.

https://tldr.sh/

Thanks for `man -t`!

It's actually 78 pages on my system (Debian, bash 4.4.12).

I've heard that OpenBSD has the best man pages that are more pleasant to read and more informative/concise.

OpenBSD man pages are what engineering documents should be. The contrast with Linux's is astounding.

This reminds me of a writeup by John Carmack. Last year he did a programming retreat where he set up a OpenBSD dev environment and tried to use the base system and the included documentation as much as possible rather than using ports and WWW†. That would probably not be so nice on a Linux system.

https://www.facebook.com/permalink.php?story_fbid=2110408722...

† Anyone else here that remembers the days when man pages and Windows help files used to be referred to as online documentation? As opposed to printed manuals.

The MSDN CDs where an endless source of amusement. The reference manuals were very good and search actually worked well. Did not feel crippled at all.

I don't know.

From `man wc`

    WC(1)                     BSD General Commands Manual                    
    WC(1)

    NAME
         wc -- word, line, character, and byte count

When in actuality `wc` outputs lines, words bytes ...

You probably referring to FreeBSD man, OpenBSD is slightly different: https://man.openbsd.org/wc.1

That still has the order wrong in the name section.

I mean, strictly speaking, the name field doesn’t document the output, but having those aligned makes the documentation much easier to read.

man -t is awesome!

IME it’s easier to focus when reading printed documentation. One can jot down notes and no temptation to go and reload Facebook/Twitter/etc. I haven’t done it often, but some commands are really worth knowing inside and out.

Indeed. Never liked reading manpages more then when I was briefly exposed to OpenBSD. Really envied them for the concise and well written documentation they have.

That let me looking into how to read them in an e-reader:

    man --html=calibre bash

Using bash's process substitution, you could also use this:

    lpr <(man -t bash)

See: https://unix.stackexchange.com/a/64011

Here is a function for mac os that outputs a pdf of a man page

    function pman() {
        man -t ${1} | open -f -a /Applications/Preview.app
    }

Lovely!

Or, if you're fine with reading it online, but don't want to run the man bash command each time (for whatever reason), and/or want to strip out the formatting characters once and for all, and/or want to use the search and other editing features of your favorite text editor on the contents of the man page, for faster navigation, copying-and-pasting snippets into scripts, etc., you can use this small shell script:

m, a Unix shell utility to save cleaned-up man pages as text:

https://jugad2.blogspot.com/2017/03/m-unix-shell-utility-to-...

Edit: Also check out the stuff about the word mu in the latter part of the post :)

In vim, I can run:

  :r !man bash | col -b

the col utility will strip backspace characters with the -b switch (along with reverse line feeds).

Right. But check what my script called m does :)

It uses col, but also redirects the cleaned-up output to a file named cmd.m (so you don't have to run that man command for the same command - like bash or other - each time), where cmd is the cmd you give to man as an arg. That file cmd.m is stored under your ~/man dir, which gets created first, with mkdir -p. More refinements possible, of course, but this was just a quick and dirty script I whipped up. For example, could check more for permission and other kinds of errors, not create the ~/man dir each time but only once, etc.

You can also display man pages in vim by default:

    export MANPAGER="/bin/sh -c \"col -b | vim -c 'set ft=man ts=8 nomod nolist nonu noma' -\""

Even better than the man page, just print out the reference manual:

    sudo apt install -y bash-doc && lpr /usr/share/doc/bash-doc/bashref.pdf

178 pages of awesome.

I’d probably add the ps2pdf command before sending it to my non postscript printer. The output of pdf to a non postscript printer would be interesting.

Cause there's gotta be a button on this thing for that thing, right?--Homer Simpson

Learning the fundamentals of your tools is a...fundamental of doing this job. If you don't want to know how your tools work, I question one's competence or desire to do this job.

Homer was wrong in his assumption. If there however does exist a button, and it works, and there is no danger associated with ignorance about its internals, then there is nothing wrong with using the button. After all, someone put it there.

> If you don't want to know how your tools work, I question one's competence or desire to do this job.

I in turn question one's competence when, instead of getting the job done, hours upon hours are spent on irrelevant parts of configuration or getting some ideal solution to work where something less elegant would perfectly suffice. Unfortunately, the folks insisting on 'mastering' ones tools tend to often be in that category.

As an analogy: I don't care if the craftsmen that fixes my house uses his hammer holding it upside down. I only care that my house is properly fixed and stays so. How that was achieved, I could not care less about.

If one is spending hours upon hours on irrelevant parts, I, again, question their competence.

If one doesn't care that the carpenter building his house is using a hammer upside down, that's a whole 'nother bunch of issues I won't go into here.

> If one doesn't care that the carpenter building his house is using a hammer upside down, that's a whole 'nother bunch of issues I won't go into here.

I'd love to see at least a small allusion to what nature the issues are made of. Because, to iterate, I'd rather have a well-built house build by an absolutely unconventially working carpenter than a mediocre house build by someone that knows how to use a hammer according to the textbook.

If I want to see nice processes and fantasies fulfilled, I watch movies. In real life, I care about results.

You are basing your story on the competence of one who doesn't know the correct way to use his tools and can then build a house well. That's not going to happen or it will take far longer to complete.

I think OP's point still stands. If the job is done to the same standards (assuming same time frame as well), what other issues does this bring up?

An apt comparison might be Jimmy Hendrix playing a right-handed guitar left-handed (i.e. upside-down) and still producing master pieces.

Hendrix knew his tools intimately. The comparison proves a point other than that which you make.

Some friends and I read the whole thing aloud, start to finish, pausing to discuss and experiment, over a handful of lunches. The Grapes of Wrath would be longer, and the Bash man page has fewer turtles.

This is the attitude we can't have nice things! Seriously, how many times do you use your shell every single day?

Very rarely. I hate the command line and actively avoid it.

Of course if your day to day job actually allows you to fully avoid bash, then by all means ignore it!

I always question what one's work day involves and how committed they are to their work when they say they hate the command line and avoid the shell. It says, to me, that they really don't want to delve very deeply into how computers work and don't care. If they care, but cannot understand, then I question their competence and whether they need to find another line of work.

Web developer checking in - no, I don't really care about the depths of how computers work. I care about competently developing the web applications my employer asks me to, for which the command line is scarcely necessary.

I'm a web developer, too. I care to know where I can speed things up or minimize things. How the code I write affects how my web applications run and which technologies I should consider or dismiss based on how it might affect the hardware we run with.

Too often, the solution of some is only to throw more hardware at the problem.

What is the problem about not knowing how computers work? I care about well-written and working code. I couldn't care less about technology. In fact, I consider it an unfortunate fact of life that programming is tied to computers.

I don't really understand this comment. Surely to write well-written code you need to understand how computers work. Just like understanding how cars work is important to be competent at servicing and repairing cars.

Saying "it's an unfortunate fact of life that programming is tied to computers" is as weird as saying "it's unfortunate that being a car mechanic is tied to cars". The job exists because of computers and cars - not in spite of it.

If you wanted a problem solving or engineering job that wasn't tied to computers then there are other options, like a mechanic, electrical engineer, mathmatition or working in any of the numerous fields of science. But a the end of the day, you're still going to need to understand the core principles of that field if you want to be effective in it.

I don't really know what this means, but I would like to because it sounds cool.

I'm a massive command line advocate (to the point that I've even written my own $SHELL) but I don't agree with your point that the command line is how computers work.

The command line is just a UI like any other - GUIs included. The way modern computers work is via API/ABI calls; via kernel syscalls and drivers separating out the responsibility of peripherals. Your command line is just an interface for managing applications that are compiled against libraries that interface with those syscalls - so in that regard using the CLI isn't any different to launching an application via a graphical icon running on a typical WIMP interface. In either case you're not making those API calls from the CLI, you're not manually managing your memory nor any of the important things that an OS does under the hood. All you're doing is using a text interface to fork() a process rather than using a mouse click to fork() a process. The difference being many CLI tools require their config supplied as command line arguments while many GUI tools don't. But even there, there are as many exceptions to that rule as there are examples of it.

> I don't agree with your point that the command line is how computers work.

I said no such thing. My point was that, if one wants to program computers, I would think one would want to be good at their job and delve deep into how their code makes computers do what they do. Showing no interest in learning the command line or the shell makes me question their interest and desire.

Uh, multiple times a day. I'm a professional programmer in a UNIX/BSD/Linux environment.

... You can leave? Kidding, but seriously: I have 20+ tmux tabs open right now. I live here; I only run X because I need a browser. (A graphical browser that handles JS; yes I've tried w3m, no it's not quite enough.)

I have no doubt there's great value in learning basic bash, but I use zsh and almost all the features I use are exactly the same commands in both bash and zsh, so I think you'd probably be okay learning one or the other thoroughly.

5931 lines here. 25 lines per page of a novel seems reasonable.

~240 pages for man bash

Google says the grapes of wrath has 464 pages.

I call that a similar ballpark. If I had an English exam with Steinbeck as one of the set texts just once I would read every word of it. I have a shell exam every damn day I work rest and play. Do you? Is skimming seeming more reasonable in that light?

An aside: I highly recommend reading the grapes of wrath

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