/dev/chat

terdon

12:00 AM

OK, that's what I was wondering. Why is bash not POSIX?

Gilles

it's the read -d feature which isn't in POSIX

a shell can have it, but it doesn't have to

I don't know offhand what bash lacks

terdon

@Gilles Yes, I understood, which made me wonder whether having extra features makes you non POSIX

I might post a question about that. I'll see if I can find out before Stephane answers :)

Presumably, because of these: gnu.org/software/bash/manual/html_node/Bash-POSIX-Mode.html

Graeme

@Gilles I will just remove that part if read -d isn't POSIX, I thought it was. I'm not sure there is a reliable way to do it POSIXly

Gilles

@Graeme there is in principle, but it's very difficult, because none of the text processing tools are required to accept null bytes

Graeme

And here was I thinking I was clever with sed "$ "\!"N; $ { s/'/'\\\''/g; s/=/='/; s/$/'/ } "

terdon

12:06 AM

@Graeme Heh, you were, that's nice!

Apparently not clever enough, but clever nevertheless.

Graeme

@Gilles I think it is more that some of the extra bash features wind up breaking POSIX conformance. You can run with --posix though.

Gilles

@Graeme you need to use --posix, sure, but even that isn't enough

terdon

@Graeme The link I posted above gives all reasons.

> There is other POSIX behavior that Bash does not implement by default even when in POSIX mode. Specifically:

The fc builtin checks $EDITOR as a program to edit history entries if FCEDIT is unset, rather than defaulting directly to ed. fc uses ed if EDITOR is unset.
As noted above, Bash requires the xpg_echo option to be enabled for the echo builtin to be fully conformant.
Bash can be configured to be POSIX-conformant by default, by specifying the --enable-strict-posix-default to configure when building (see Optional Features).

Gilles

Trap handling is probably broken, only ksh gets it right

terdon

@Gilles You mean this?

> 46 The arrival of SIGCHLD when a trap is set on SIGCHLD does not interrupt the wait builtin and cause it to return immediately. The trap command is run once for each child that exits.

Graeme

12:09 AM

@terdon so you need build options, good to know.

terdon

@Graeme Apparently

Gilles

12:27 AM

0

A: How do I source another process's environment variables?

In this answer, I assume a system where /proc/$pid/environ returns the environment of the process with the specified PID, with null bytes between variable definitions. (So Linux, Cygwin or Solaris). Zsh export "${(@ps:\000:)$(</proc/$pid/environ)}" Bash, mksh while IFS= read -r -d "" PWD; do...

I didn't find a non-Rube-Goldberg way of dealing with null bytes posixly

terdon

12:39 AM

@Gilles Could you explain the zsh magic please?

Gilles

@terdon edited

terdon

@Gilles Thanks.

Your bash one seems to fail on exporting newlines

It will export the entire variable correctly but seems to convert a newline to a space.

Nope. Sorry, quoting idiocies on my part.

mikeserv

1:00 AM

@Gilles: . <<ENV /dev/stdin\n$(cat </proc/$pid/environ)\nENV\n

Kinda rubey. too, I guess.

If that doesn't handle null just add |sed -z or similar.

I think the subshell should handle the \0 though.

So probably: . <<ENV /dev/fd/0\n$(echo 'IFS=' ; cat /proc/$pid/environ ; echo 'unset IFS')\nENV\n could get it. It's the same as set, right?

speaking of which...

Gilles

1:18 AM

@mikeserv completely broken since the entries in environ are null-separated, not newline-separated

@mikeserv sed: invalid option -- 'z'

mikeserv

`. <<ENV /dev/fd/0\n $(tr '\0' '\n' <proc/$pid/environ)\nENV\n

Gilles

I have no idea what you're trying to do here, but it's not helping

mikeserv

Sorry - its not easy on the tablet. I do suspect though that if you put that in sh the \0 wouldn't pass the subshell.

You don't have -z? Weird - I got that.

@Gilles you should look again. Don't know why I didnt think of tr in the first place. If you havent already noticed - I'm a little dense sometimes. But I am persistent.

Gilles

@mikeserv and what happens to values that contain newlines?

you can swap newlines and nulls with tr '\0\n' '\n\0'. It's a useful trick sometimes. But then you need to find a way to manipulate the data that works even when there are null bytes.

All GNU tools are null-safe, but POSIX doesn't mandate it

mikeserv

Nothing.

No need.

It doesn't come quoted?

I know that. But I thought the environ file was quoted?

As long as the values are quoted the here-doc won't do anything to the newlines.

Gilles

1:32 AM

@mikeserv no, it's just null-separated records

why would it be quoted?

it has nothing to do with the shell, it's a kernel interface

mikeserv

Damn. I guess I'm thinking of set. So you'd have to do it with used after all -

I know that, I just still thought it came quoted.

Still. . <<ENV /dev/stdin\n$(sed '$!H;${x;/$^\|\x00$$[^=]*$.$[^\x00]*$/s//\1="\2"\n/g}')\nENV\n

That might do it.

I dunno. Its hard enough typing it on the tablet, much less testing it.

Gilles

@mikeserv I don't think so. What if a value contains "?

mikeserv

Oh, then I guess you use \x47 instead.

Gilles

that's not the issue

you're barking up the wrong tree

heredocs won't help you there. Sure, you can use a heredoc, but a string will do just as well.

Graeme

I had to throw in the towel on this one. The solution can be done with a combination of @Gilles tr trick and sed -n l. If you then pipe to a long sed script, read each line and pass it through printf and eval you will get it.

mikeserv

1:45 AM

OK. It would be better to save the ENV with set when the process is invoked of course. You wouldn't need to do all the parsing. Its served on a quoted silver platter.

Gilles used tr too?

A heredoc will help because it won't screw up the quotes and .dot can read a file.

I think the above should do it all thought.

If you use \x47 instead of "

Sorry. That's octal. \x27

You could use a pipe too - but then how do you get it in the current environment? Guess you could set it on the other side of the pipe then output set

Gilles

@Graeme you're still assuming that sed passes null bytes through unscathed

in which case, you might as well assume a null-safe awk and save yourself a lot of trouble

mikeserv

What's that mean?

What's the link?

Gilles

have you programmed in C?

C uses the null byte as an end-of-string marker

old Unix utilities just read lines as strings. If a line contains a null byte, it effectively marks the end of that line.

POSIX doesn't require any of the text utilities to cope with null bytes in the input

mikeserv

No way. I can interpret some of it - I know null means end though. That's why the subshell will strip it for you. Well, not in ash though.

Zsh that is.

Gilles

zsh is the only usual shell that copes with null bytes in strings

strugee

1:52 AM

<3 zsh

mikeserv

I know. That's why I suggested you try the cat thing in sh. But it doesn't handle the quotes. Still, it gets a lot easier after that.

Graeme

I think `sed` is required to be null safe in this case. The POSIX manual says:

>Escape Sequences and Associated Actions ( '\\', '\a', '\b', '\f', '\r', '\t', '\v' ) shall be written as the corresponding escape sequence; the '\n' in that table is not applicable. Non-printable characters not in that table shall be written as one three-digit octal number (with a preceding backslash) for each byte in the character (most significant byte first).

mikeserv

2:06 AM

Probably : sh <<\CMD\n ( tr '\n' '\\n' </proc/environ ) | sed '/^([^=]*).(.*)/s//\1=\x27\2\x27/;s/\\\\n/\n/g'\nCMD\n

strugee

PSA: I've just added "use this tag for questions not applicable to other distributions" to the end of arch-linux.

mikeserv

That's probably pretty close to getting set equivalent output. Safe the newlines with tr instead of the nulls and let the subshell strip those for you. It's one idea. Still, its much better to do at process launch - then all you have to do is ENV=set and eval it later whenever.

strugee

sound OK? if so I'd like to add it to other distribution tags (e.g. redhat, debian, etc.)

mikeserv

That's a great idea.

strugee

ok, I'll add it to the other wikis

I like how @slm is in the top answerers for Debian but he doesn't even use it

mikeserv

2:11 AM

Well, he's a very active answerer and its a very active topic, but I appreciate the irony as well.

slm

Yes for shame everyone that uses Debian. I've only booted it for the first time ever in the last month or so.

in VM

I've only ever used RH, SuSE, Mandriva, Mandrake, and Slackware

pretty much everything but Debian/Ubuntu. My wife and kids use Ubuntu.

The nicest OS I've seen though is PCLinuxOS

strugee

@slm <troll>everything but Debian, Ubuntu and the best distribution of all</troll>

you forgot Gentoo and LFS too

slm

Yes i forget about Arch

strugee

but I see your point :P

slm

I used Gentoo too

strugee

2:15 AM

@slm really? how was it?

slm

I'm still waiting for it to compile 8-)

strugee

also: no reason to keep gnome-3.6 and gnome-3.8, right?

slm

gentoo was very nice but building from src was a pain to me

sabayon is a nice compromise

but I like living on contents not islands

strugee

I really want to try Gentoo, but I'm afraid that I'll like it and then I'll spend way too much time waiting for compilations. #gentoo

Tweeted by strugee2 on October 28, 2013 at 12:19 AM

mikeserv

That reminds me - @Graeme - did you ever get Terminology to come together?

Graeme

2:22 AM

@mikeserv nah, not yet. I built it with the Debian e18 libs but no dice. I turned out that elementary was actually e17, so I compiled that one from source. Still no dice. I think I need to do the whole lot from source. Or just wait until someone gets around to packaging it.

slm

@strugee If you like Arch I would assume you'll like Gentoo. The install to me was a pain to get started, not very clear, but it was nice and fast once you took the time to build things. I eventually gave up on it though, the building is just too painful to me

mikeserv

I think you do too - they're chatty builds, but super easy.

strugee

@slm I think so too

mikeserv

I want to do something like I did with that btrfs seed / tmpfs hack but as a package manager.

Essentially all a package manager does is tell the filesystem where to put what file. If it could be handled by the filesystem...

Still, I'm way too lazy to see anything like that through.

And dependency tracking of course, I guess, but that could be tracked in the filesystem too.

With subvolumes.

strugee

@mikeserv I have no idea what you're talking about, because I only vaguely remember you talking about that. but you should look into OSTree

it might be vaguely what you're talking about. I don't know.

Graeme

2:33 AM

@mikeserv, here is the error I get from `terminology`:
`CRI<7081>:elementary elm_win.c:2858 _win_constructor() Software X11 engine creation failed. Trying default.`

Any ideas?

strugee

holy shit. it happened.

look at MSO:

(aaand that's the same image)

Braiam

@strugee yeah, they are still iron out bugs

if you want rep in MSE, just ask :P

mikeserv

@Graeme - mostly that you should just do the whole build.

strugee

@Braiam :P

mikeserv

Sorry. It's just - that's how I did it.

Graeme

2:51 AM

Yeah I would like it to work with as many packaged sources as possible. The more stuff you compile, the more deps you end up having. When they get upgraded, you end up having to recompile. Is a pain in the ass.

mikeserv

3:24 AM

I would generally agree, but their builds are pretty self contained.

@Graeme - I found that one post - is it just me or is there pretty much nothing in /proc/1/environ anyway?

Graeme

@slm, I see some pretty backward logic here - unix.stackexchange.com/questions/125155/pattern-matching/…

@mikeserv nope not much there, are you still thinking about parsing enviroments?

slm

@Graeme - I would've done it exactly the way you suggested. I asked the OP about it as well. He seems to be having issues with he file sizes though.

Graeme

@slm he probably wants to match in the first column (although I have a feeling he doesn't even realise it). I was just left squinting when he said he didn't want to use grep because of the other solution.

slm

@Graeme Yeah that made little sense to me as well

Graeme

Not as if you can add these things called arguments that massively change the way a program behaves or anything.

slm

3:31 AM

Jason found a dup anyway, you answered on the dup too 8-)

I don't understand why he's asking how to do this from a perl program either

oh well, slow night when we're fighting over answering these gene Q's 8-)

Graeme

Yeah, been quite slow on here all day today I think. Nevermind, its way past my bed time anyway I was gonna call it a night before I saw that and thought "that's easy". This time though...

0

Q: Downgrade USB 3.0 to USB 2.0 in ubuntu

I have USB 2.0 device when I plugged this device into the USB 3.0 port of my system then system gets hanged, after researching many of the solutions says that you can downgrade USB 3.0 to USB 2.0. But I didn't get any specific documentation for related to downgrading process. How can I downgrade...

When he says downgrade the ports, is there no way to force the USB 2 driver to be used for a USB 3 port?

mikeserv

Of course. Not much? Mine is only TERM=Linux

@Graeme I'm betting that's set by a file.

Graeme

@mikeserv I get a few more than that BOOT_IMAGE is one.

mikeserv

@slm - what's in your /proc/1/environ?

BOOT_IMAGE...

I still think my sed thing would do it with any one. But now I'm wondering what the hell is so special about this guys proc/1/environ.

slm

BOOT_IMAGE=/vmlinuz-3.13.7-100.fc19.x86_64LANG=en_US.UTF-8RD_TIMESTAMP=1397222729129935 2356578PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin

mikeserv

3:45 AM

I answered another question of his earlier today. Well...

If you'd call it an answer. It was a man copy/paste.

Now thats useful. Thanks @slm and @Graeme.

slm

@Graeme I had the same thought too, but didn't see a way to do this.

@Graeme - lshw shows the drivers being used for the various hardware

on my USB2 only laptop

         configuration: driver=ehci-pci latency=0

Graeme

@slm I'm just wondering what happens if you run an old kernel on a machine with USB 3. Does it fail to recognise the ports at all or does it just treat them like USB 2?

slm

The only thing i could conceive of was perhaps the ehci-pci would take switches

               capabilities: usb-2.00

is shown in my output

Graeme

The USB 3 driver is xhci_hcd AFAIK

You could always try hiding the module

slm

I don't have any USB 3's handy

You can usually pass options to the drivers, I'm guessing you could tell the xhci_hcd driver to only allow for 2 capabilities

Graeme

3:52 AM

I get all three drivers showing up when I do lspci -v

ohci-pci, ehci-pci and xhci_hcd

I think different ones are used depending on what is plugged in

You could try hiding /lib/modules/3.13-1-amd64/kernel/drivers/usb/xhci-hcd.ko and see what happens.

Anyways, done for today.

slm

I don't have these drivers

xhci_hcd

3.13.7-100.fc19.x86_64

mikeserv

4:18 AM

@Graeme depends on the application.

Many usb3 applications are actually PCI addons.

Those generally fail entirely.

But truly on-board usb3 applications should be managed to some degree by the firmware and so you'll get USB2 functionality.

@slm's showing off his nearly up to date kernel to all of these Debianers.

I'm still on 3.13 too I think.

slm

4:36 AM

I cannot find the module xhci_hcd. Puzzled as to why this would be missing.

mikeserv

Do you have usb3?

Don't mean to insult. Its just a habit to ask stupid questions.

slm

no i don't

$ sudo modprobe -r xhci_hcd
modprobe: FATAL: Module xhci_hcd is builtin.

Would seem that this module is builtin

mikeserv

I meant the hardware.

You might have the other one...

Forget what its called.

slm

nope no usb3 hardware

mikeserv

Starts with an e I think.

strugee

4:41 AM

...Ethernet?

slm

ehci-pci

strugee

nevermind

mikeserv

Well. Why would you have xhci then?

No. The brand actually.

Ethernet. Haha.

slm

Sorry I was looking for the kernel module on disk I wanted to interrogate it to see what capabilities it had (i.e. what options it would accept)

mikeserv

Well, do you have the header files? Don't know why modprobe or udev would source it for you if you don't have the hardware. Get the headers though and you should be able to play around with all of the modules.

slm

4:45 AM

I like using modinfo <mod> for the param listings

mikeserv

4:56 AM

Did it work then? Definitely sorted /proc/$$/environ

Don't know why Gilles thought it wouldn't work, but it handles everything I throw at it.

. <<ENV\n$(sed -rn 'H;${x;s/(^|\x00)([^=]*.)([\x00]*)/\2\x27\3\x27\n/gp}' /proc/self/environ)\nENV\n

Anybody know why that might fail?

It handles terminal escapes and newlines special shell characters for me anyway...

Though it should be . <<ENV /dev/stdin

And the last bit should be [^\x00]*

strugee

5:30 AM

hmm, Fedora's restructuring looks interesting and promising. blogs.gnome.org/uraeus/2014/04/16/…

@slm ^

anyway, bedtime now. night all.

slm

@strugee - thanks for the link, was just reading it, looks interesting

Gilles

7:08 AM

@Graeme no, that's about all the other non-printable characters

> The input files shall be text files

Text File

A file that contains characters organized into one or more lines. The lines do not contain NUL characters and none can exceed {LINE_MAX} bytes in length, including the <newline>. Although IEEE Std 1003.1-2001 does not distinguish between text files and binary files (see the ISO C standard), many utilities only produce predictable or meaningful output when operating on text files. The standard utilities that have such restrictions always specify "text files" in their STDIN or INPUT FILES sections.

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