Ask Ubuntu General Room

Chances are, you just installed something from a trisquel repo and that brought in a new /etc/os-release file and that's why you see a different distribution name.

orlp

3:35 PM

who flags 'fucking' and 'WTF'? are we really this thin-skinned here?

Journeyman Geek

@terdon and trisquel spash screens and...

I donno if the DE is the same.

guess not

terdon

@orlp Yes, unfortunately. This particular room has a very low threshold for profanity. Don't look at me. I didn't make this rule, I just have to enforce it.

Journeyman Geek

@orlp keeping calm is always good advice tho

terdon

@JourneymanGeek Yeah, OK, but that's all decorative. Nothing essential. Still running the same OS just with a different paint job.

Journeyman Geek

you're going to break things more frustrated than not

orlp

3:36 PM

@terdon flags are not to enforce room rules, only for site-wide rules

@JourneymanGeek I can't disagree with that

Journeyman Geek

@terdon randomly changing distros....

terdon

@orlp Oh really?

:P

Zacharee1

So I need to get the result of a command to be appended to a file

but this command doesn't seem to work:

cp /data/media/0/Documents/LGAppBak/LGQuickTools.apk /system/priv-app/LGQuickTools/LGQuickTools.apk >> /proc/self/fd/$OUTFD

(this is Android)

Journeyman Geek

@orlp there's no real concept of site/room culture as far as the powers that be can be concerned

@Zacharee1 OT OT OT

also, should that have an output?

terdon

@Zacharee1 WHat output? cp doesn't have any

Zacharee1

3:37 PM

cp commands? maybe not...

it does give errors though, right?

so in theory, if I have an error, will that work?

Journeyman Geek

but if it worked, no errors, no?

terdon

Only if it fails or if you use -v but both go to stderr, not stdout, so you need 2>> /proc/self/fd/$OUTFD

orlp

@JourneymanGeek I mean there's a very simple test: if I make a room with a rule that the word 'abortion' is off-limits I am free to kick people for that as a room owner, but it'd be abuse to use flags for that

Zacharee1

@terdon ah thanks

Zanna

I didn't realise that the -v output was on stderr...

Journeyman Geek

3:38 PM

@orlp language like that is unloved in most places

Zacharee1

so I can use -v and it'll give me status?

Journeyman Geek

a lot of people use the site at work

Zacharee1

as well as errors?

terdon

@orlp Yes and no. Actually, the rules about profanity have gotten considerably more stringent network-wide.

orlp

@JourneymanGeek I just used 'abortion' as an example, what about 'train'?

Zanna

3:39 PM

@Zacharee1 not status, it will print which files are going where

Zacharee1

@Zanna that's what I meant :p

Journeyman Geek

@orlp depends on the context, but there's acceptable contexts for both, but not the F word

or the C word

terdon

@orlp It's up to the handling mod's discretion. But yes, in general, if a local room has its own rules that are different from the site's, using flags to enforce those would be considered abuse. By me, anyway.

Zanna

@Zacharee1 yeah, but apparently it will be on stderr not stdout, TIL

Journeyman Geek

or my favourite hokkien profanities, once anyone groks it...

terdon

3:40 PM

And I have called it so in the past in the 9th byte as I recall.

Zacharee1

@Zanna TIL too lol

terdon

@Zacharee1 do you want output or status?

Zacharee1

apparently cp is an unknown command....

Journeyman Geek

lol

Zacharee1

@terdon I want it to tell me the errors

which it did

so I've got what I need

terdon

3:40 PM

OK

Zacharee1

the SH noob goes back to SHing

Journeyman Geek

shiiiiiing

Zanna

er...

zanna@monster:~/playground$ cp -v foo copying >/dev/null
zanna@monster:~/playground$ cp -v foo copying 2>/dev/null
'foo' -> 'copying/foo'

Zacharee1

Android?

uh

well it's a valid command....

Zanna

not Android

Zacharee1

3:42 PM

because it works in the shell

Zanna

no I'm just saying, the -v output isn't in stderr here, but I'll shut up

you're fine, carry on

Zacharee1

hue

terdon

@Zanna Yes, you're right. My bad, it seems to be going to stdout after all.

Zacharee1

can I get both?

like a >> 2>>?

terdon

@Zacharee1 Yes. >file 2>&1

Zacharee1

3:44 PM

ok

Zanna

@terdon I think you don't want that first 2?

Zacharee1

do I actually need to specify a file?

terdon

32

A: How to redirect stderr to a file

There are two main output streams in Linux (and other OSs), standard output (stdout)and standard error (stderr). Error messages, like the ones you show, are printed to standard error. The classic redirection operator (command > file) only redirects standard output, so standard error is still show...

Zacharee1

oh wait

derp

Zanna

the other one

terdon

3:44 PM

Whoops

Zacharee1

woke up at 4:45 today so I'm derping

Zanna

command > file 2>&1

Zacharee1

the OUTFD is my file...

thanks

the question is, why is cp an unknown command??

Zanna

hahaha oh dear

Zacharee1

so this?

command >> /proc/self/fd/$OUTFD 2>>$1

(I need to append)

terdon

3:46 PM

No, this:

command >> /proc/self/fd/$OUTFD 2>>&1

Zacharee1

oops

terdon

But why are you writing to /proc in the first place?

Zacharee1

because that's where TWRP gets its output to display

well that command broke TWRP...

Zanna

:(

Zacharee1

hmm

So SH doesn't like the double pipe thing

uhh

well it "works" if I use $1 instead of &1

terdon

3:51 PM

@Zacharee1 this would really go much better if you started from the beginning and explained what you're actually trying to do.

Zacharee1

but then I don't get the stderr status at all

terdon

And what tools you're using.

Zacharee1

@terdon lemme just post my script

#! /sbin/sh

OUTFD=$2

readlink /proc/$$/fd/$OUTFD 2>/dev/null | grep /tmp >/dev/null
if [ "$?" -eq "0" ]; then
  # rerouted to log file, we don't want our ui_print commands going there
  OUTFD=0

  # we are probably running in embedded mode, see if we can find the right fd
  # we know the fd is a pipe and that the parent updater may have been started as
  # 'update-binary 3 fd zipfile'
  for FD in `ls /proc/$$/fd`; do
    readlink /proc/$$/fd/$FD 2>/dev/null | grep pipe >/dev/null
    if [ "$?" -eq "0" ]; then

I'm trying to copy files using a TWRP update ZIP

terdon

What's TWRP?

Zacharee1

custom Android recovery

terdon

3:52 PM

And why are you using $2 there? Where's $1?

@Zacharee1 Ah, right. Yes.

Zacharee1

@terdon no idea. I'm stealing some of this from SuperSU's code

can I just do this:

terdon

@Zacharee1 Well, $2 is the second positional parameter. For example, if you run script.sh foo bar, then $2 will be 'bar'.

Zacharee1

command >> file 2>> file?

@terdon yeah I get that

but it does work

supersu set VARNAME to $1, but I'm not using that piece

terdon

Ummm

You keep printing stuff to $1. What is that?

Zacharee1

nothing

got rid of it

it's this now"

/sbin/cp -v /data/media/0/Documents/LGAppBak/LGSystemUI.apk /system/priv-app/LGSystemUI/LGSystemUI.apk >> /proc/self/fd/$OUTFD 2>> /proc/self/fd/$OUTFD

which works

to tell me that cp is an unknown command....

terdon

3:54 PM

How do you tun the script?

@Zacharee1 Well, you're telling it to use /sbin/cp for some reason. Does that exist?

Zacharee1

yes

so does cp

neither works

@terdon TWRP looks for an update-bunary file in the ZIP

gtg for a bit

terdon

Eeek! OK, never do for i in $(ls)...

In your case, all you need is for fd in /proc/$$/fd/*

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