should have "run" away

mikeserv

Mar 14, 2014 02:18

What was I doing to poor sed? I highlighted in bold because it's super-important people understand that . will run everything you point it at. Saying "source doesn't run the script" was scary.

slm

@mikeserv you're delivery needs work

and you back it up with 0 facts

terdon

@mikeserv it doesn't, it sources it. That results in statements being executed but its relationship to the parent shell is completely different

slm

show that this is the case, otherwise you're just rebutting it to me and making me have to do ALL the work

mikeserv

It is executed - run - in the same way any script is run - either in the current shell process or a child.

Ok, slm, that's a very good point. I can do that.

terdon

@mikeserv try this:

mikeserv

Mar 14, 2014 02:20

If I'm wrong I

terdon

echo xclock > foo; source foo

slm

sourcing takes each of the commands and runs them one by one in the context of the shell as children

mikeserv

'll delete it.

terdon

@mikeserv basically, we kinda expect people to do their homework before posting comments.

And foget that xclock thing, that works, hmmm.

slm

@mikeserv - yes but instead of using DOES and bold you could be a little bit more constructive on the site

mikeserv

Mar 14, 2014 02:21

Oh, yeah, I'm not totally sure of, which is why I said "as far as I know - I could be wrong" - thew important part is that it's run. leading people to believe otherwise is scary.

slm

yes but your choice of words is misleading to passer bys

mikeserv

DOES and bold were the important things.

slm

You're being a drumhead w/o any additional facts and making me have to prove you wrong

mikeserv

No, it was very clear - the script is run!

slm

instead prove that I'm wrong with some actual facts

Braiam

Mar 14, 2014 02:23

@mikeserv be humble when you are not sure, the use of bold and CAPS are irrelevant whenever you aren't 1000% sure you should be using them

mikeserv

Ok, that is a good point. I think terdon just did thouh.

I am sure that the script is run - I am not sure that the difference is only that dropped safety mechanism.

casey

Here is a fact: (an example of how to back something up)

>. (a period)
. filename [arguments]
Read and execute commands from the filename argument in the current shell context.

terdon

@mikeserv I did?

Braiam

you got to love zsh:

mikeserv

O

casey

Mar 14, 2014 02:25

source: bash info manual

Braiam

> . file [ arg ... ]
Read commands from file and execute them in the
environment.

If file does not contain a slash, or if PATH
shell looks in the components of $path to find
containing file. Files in the current directory
unless `.' appears somewhere in $path. If a
`file.zwc' is found, is newer than file, and is
form (created with the zcompile builtin) of file,
are read from that file instead of file.

mikeserv

I'm doing it now.

slm

The diff. b/w a source and a execution is that the commands get run directly as child processes within the context of the current shell, when you run them in a script, they get executed as children under an entirely different shell

Braiam

> source file [ arg ... ]
Same as `.', except that the current directo-
searched and is always searched first, before
$path.

mikeserv

They are run.

Braiam

Mar 14, 2014 02:26

they are the same, just that sources look first in the current directory and then in the $PATH

casey

execute is the terminology used

mikeserv

He used "source doesn't run a script"

It does.

casey

This builtin is equivalent to source.

(referrering to dot)

slm

source isn't running a script, it's reading the contents of that file and running the commands one at a time

terdon

@mikeserv not quite:

> The command source does not run another script. Merely it pulls the contents of this other script into this script, and then runs its content as if it was originally part of the calling script.

casey

Mar 14, 2014 02:28

and as @slm points out, the context of the execution is quite important.

terdon

He said it does not run another script.

slm

using source or . is equivalent to an include

mikeserv

Very important!

Braiam

@slm oh dear, bringing up C, ain't ya?

;)

terdon

@mikeserv since the conversation is getting chaotic, use the arrow to the left hand side of posts to answer them so we know which statement you are answering

slm

Mar 14, 2014 02:29

Can we have a moratorium on empahsis' 8-)

mikeserv

That was why I didnt want a casual reader to mistake "source doen't run a script" for "nothing will happen."

terdon

@mikeserv read what he wrote, he said it doesn't run another script.

mikeserv

He's technically right - except that his wording was dangerous, in my opinion.

slm

@mikeserv - the attitude you're taking is off, IMO. I wrote the A and now you're putting a big, incorrect warning at the bottom, forcing me to have to do your homework

terdon

He's technically right means he is actually right. Right?

slm

Mar 14, 2014 02:31

@mikeserv - so the next time this happens do some follow up with the author first before jumping the gun

mikeserv

Take it on, then. No I am doing the homework now. Or I would if this window would be stop beeping at me.

slm

ha

Braiam

ok, now everyone stop

slm

the beeping made me laugh

mikeserv

I didn't jump any guns - another script is run.

terdon

Mar 14, 2014 02:32

@slm @slm @slm @slm@slm@slm so there :)

mikeserv

In the current shell environment.

slm

I have it muted

terdon

damn

strugee

@slm sed, it's okay now. show us on the doll where the shell touched you.

Braiam

@mikeserv please, if you are not going to continue a constructive conversation, please just move on

terdon

Mar 14, 2014 02:33

In his defense, he's not being very aggressive here. Just slightly stubborn.

mikeserv

This is not constructive? You do not believe another script will be run if I source it from a different one?

slm

I'm trying to keep this light

Braiam

I just don't like things to scalate

slm

me neither

perhaps it's the word run that's the hang up?

Braiam

@mikeserv is just not! read the man page, and documentation, how can you interpret them as "running another script"?

strugee

Mar 14, 2014 02:34

@slm you may have never said it but we assume it. you're good

mikeserv

Thanks, terdon. Me either, I didn't mean any harm - I don't bear anyone ill will - I like argument - it's how you get correct.

casey

. file <- my shell executes the contents of a script. ./file <- my shell spawns a subshell to execute the contents of a script.

slm

yeah let's not argue, let's discuss in a light and friendly manner

we don't need any hostile arugments here, let's break it down so that ppl understand what's going on, w/ examples works best, saying things work a certain way with being to demonstrate them is discouraged

casey

example:

casey@convect ~ % cat setvar.sh
#!/bin/bash

TESTVAR=testtest

casey@convect ~ % ./setvar.sh ; echo $TESTVAR

casey@convect ~ % . ./setvar.sh ; echo $TESTVAR
testtest

slm

@casey - yes that's how I would put that too

casey

Mar 14, 2014 02:36

as I'm not exporting TESTVAR, it is only visible in the shell that sets it

Braiam

@casey why the .sh termination if it's a bash script ;)

casey

@Braiam why not? :)

strugee

(just for the record, I did not make that up myself. chat.stackexchange.com/transcript/127?m=14131611#14131611)

Braiam

@strugee O_O

casey

@Braiam a better question is why did I write a bash script to run in zsh :)

slm

Mar 14, 2014 02:38

This is kinda of a datapoint:
$ strace -s 2000 -o m.log . somefile.txt
strace: exec: Permission denied

I tried to run . somefile.txt

the contents of that file?

strugee

@Braiam yeah

mikeserv

. <<-\SCRIPT /dev/stdin
script=script1 ; echo $script is run
. 3<<\SCRIPT /dev/fd/3
script=script2 ; echo $script is run
SCRIPT

Braiam

@slm is builtin, it can't spawn a new process

slm

$ more somefile.txt
echo "hi mike"
echo "sam sourced this"

mikeserv

Oh - you need a <tab> in front of the final SCRIPT

Braiam

Mar 14, 2014 02:39

@casey err... yeah...

@mikeserv could you drop the caps' please (again)

slm

@Braiam that's kinda my point

Braiam

we are not blind

mikeserv

All commands are run - why? Well, that's just how I denote heredocuments.

slm

pls stop w/ the bold

how many times do i have to ask

casey

@mikeserv all shell commands are run, see slm's example where echocannot be run

slm

Mar 14, 2014 02:41

I DONT NEED THEM I CAN READ!

DO YOU LIKE IT BACK?

casey

source cannot necessarily execute an arbitrary script

mikeserv

I don't care. But that was just the code.

It does.

That's its job.

Braiam

@mikeserv I'm kinda feeling your only point to arge is a unclear semantic, no an inaccurate answer

mikeserv

Exactly!

Braiam

the answer is correct, just upvote it!

mikeserv

Mar 14, 2014 02:42

I did.

Braiam

we are not ELL to discuss semantics

mikeserv

Well, another script is run, and its a little scary to suggest otherwise.

The rest was awesome.

Braiam

run == execute for most of us, depending the context it could also mean parsed, etc.

slm

I'm still lost

Braiam

just that something is actioned and some result is expected

if it doesn't it just don't run

mikeserv

Mar 14, 2014 02:44

It is executed - every command therein - even exec. It's not exec(3)'d - it diesn't replace the process.

terdon

@mikeserv is English your native language? No offense if it is, but @slm's wording was quite precise.

mikeserv

It does run. Of course. My keyboard sucks. It's this little portable Logitech dealie with a builtin mousepad - you're on my tv.

slm

huh?

terdon

cool, I've always wanted to be on TV. Has it been 15 minutes yet?

Braiam

@mikeserv are you the NSA that we are on your TV?

mikeserv

Mar 14, 2014 02:46

I don't think so - everyone here keeps talking about exec(3) but is there a literal run(3)? The wording was ambiguous in that sense.

Yeah.

NSA.

strugee

@slm HDMI?

Braiam

@mikeserv that you should ask to the ones that make the wonderful thing called UNIX ;)

slm

I wish I was on the playboy channel

4

Braiam

@slm O_O

terdon

Seriously though, the wording was that it doesn't run another script, as in starting a new subshell but instead brings the commands into the current one. That's something we all agree on right?

@slm No offense but I'm glad you're not :P

mikeserv

Mar 14, 2014 02:48

Well, I preferr pedantic arguments to porn I guess. Says quite a lot about me I suppose.

It does run another script.

terdon

We're all geeks here, pedants by trade and nature

strugee

if we're going to do this argument anymore I need some popcorn

slm

I prefer not arguing at all and working it out in a calm and carefree environment with fellow humans that I would consider my friends

Braiam

gives some to @strugee

strugee

aw thanks

Braiam

Mar 14, 2014 02:49

<--- always have popcorn

terdon

@mikeserv it depends on what you mean by running. Normally, running a script means starting a subshell for that script. That is not the case for source

slm

I was thinking of a beer to go with my playboy

@terdon boom chick booom chick chick.....not sure how to type the music...

terdon

Well, there's a mental image I could have done without :)

slm

me w/ a beer?

mikeserv

I like arguing with my friends. It's how I learn. Sorry to bum everyone out. I didn't mean anything was bad - I don't read bad posts far enough in to make it to the comment block.

slm

Mar 14, 2014 02:51

there a compliment, I'll take it

mikeserv

I didn't say run - slm did.

I used the same terminology.

That's all - I referenced your language, dude.

slm

I didn't have any issues with my terminology, dude

terdon

@mikeserv we all like (friendly) arguments, so, how do you defend this statement?

> POSIX's . DOES run the other script in the current shell environment.

mikeserv

Well, I think first it needs an accusation.

slm

That was the one that should've included a link to a standard somewhere

What is your line of work? I'm thinking lawyer?

mikeserv

Mar 14, 2014 02:54

NAME

dot - execute commands in the current environment
SYNOPSIS

. file

DESCRIPTION

The shell shall execute commands from the file in the current environment.

If file does not contain a <slash>, the shell shall use the search path specified by PATH to find the directory containing file. Unlike normal command search, however, the file searched for by the dot utility need not be executable. If no readable file is found, a non-interactive shell shall abort; an interactive shell shall write a diagnostic message to standard error, but this condition shall not be considered a syntax error.

slm

Why is everything so adversarial?

mikeserv

pubs.opengroup.org/onlinepubs/9699919799/utilities/…

Adversarial? I was just asked to defend myself.

In any case, there's the homework.

slm

I don't see anything here that's disagreeing w/ what I characterized?

terdon

@mikeserv indeed it is. And I was contesting your statement about not having used run. Which you then explained as using @slm's terminology.

mikeserv

Didn't I?

slm

Mar 14, 2014 02:56

Can we pls use the replies?

casey

I wish my wife wasn't asleep, I'd make some popcorn

slm

the little arrow to the left?

casey

@slm like this

mikeserv

@slm You said it's not run. It's run - apparently executed, even. And yeah, sorry.

terdon

@casey How can she sleep when someone is wrong on the internet!

2

slm

Mar 14, 2014 02:57

The file is not run, the lines inside it are

strugee

https://lh3.ggpht.com/-Rc8k_D3yYoE/Tw4IyOKMysI/AAAAAAAAAls/awgasVzJMfA/s320/Stephen-Colbert-Popcorn.gif
(filler text)

mikeserv

@terdon I'll never understand it.

casey

@terdon @terdon I wonder that myself. this is serious business.

slm

nice

terdon

OK guys, how about this: @slm will edit his answer to remove the ambiguity and @mikeserv will delete his comment. Deal?

mikeserv

Mar 14, 2014 02:57

@slm What...?

slm

"The shell shall execute commands from the file in the current environment. "

casey

@terdon can we call the agreement the U&L Treaty of 14 March 2014?

slm

what am I missing?

terdon

@mikeserv He means that the commands within the file are executed but the file is not walked as a script.

Braiam

@mikeserv is a reverence to some comic xkcd.com/386

mikeserv

Mar 14, 2014 02:58

@terdon Yeah - that was my suggestion when iI came in here. I'd be more than happy to - it was a good post!

slm

as in chmod +x somefile

./somefile

terdon

@casey hang on, see how it goes first ;)

casey

:)

slm

can i get some of that popcorn?

mikeserv

@terdon I don't understand the difference.

slm

Mar 14, 2014 02:59

See it was the use of run

terdon

@slm sorry, edited

slm

LOL can you give me the link to what A we're talking about?

strugee

@slm probably

mikeserv

@slm All that bugged me about it was that it said something I thought might be misinterpreted to wind up with someone's shit getting deleted.

@strugee And no, not a lawyer. I was an Army helicopter mechanic.

strugee

@mikeserv it was @slm that asked. not me.

slm

Mar 14, 2014 03:01

I asked what you did

mikeserv

@strugee my bad. Like I said - this keyboard sucks.

slm

why is your username mikeserv?

if I may ask

mikeserv

@slm my bad. Like I said - this keyboard sucks.

terdon

@mikeserv the difference as I understand it (and my understanding is quite limited, I'll be the first to admit) is that a script is run as a, well, a script. With it's own subshell and PID. While sourcing will simply read the commands in the other file and incorporate them into the script doing the sourcing. Kinda like #includes for C as slm said before.

casey

Yea, when I hear the phrase "runs another script" I can only interpret that as a spawned process with its own PID, and I cannot reconcile that with what source does.

slm

Mar 14, 2014 03:04

read(3, "#!/bin/bash\n\n. somefile.txt\n", 80) = 28

that's from an strace, it's just reading the file in, not running it

mikeserv

@slm I was - and guess I still am - a geek as a kid. My cousin had an ISDN line IRC server, and broadband internet had just come out and you didn't get DHCP addresses then, we got static IPs when my dad hooked up DSL. So my cousin asked me to share the load, and I took mikeserv, alongside operserv and the rest of the bots. Don't know why, my name's Frank.

slm

good story

open("somefile.txt", O_RDONLY) = 3

mikeserv

@slm I consider that thinking fallacious, because the shell does that, probably, but it's not guaranteed and is usually a result of the hash bang. No hash bang, and you might not have a new process at all.

terdon

@mikeserv huh? Really?

slm

frank it doesn't matter what we think, that's what the computer is doing

mikeserv

Mar 14, 2014 03:06

@slm As far as I know, that's implementation dependent. And besides, I'm pretty sure you can get the exact same behavior with . .

slm

I just showed output from an strace

mikeserv

@slm . a #!/bin/dash file.

slm

that isn't what I did there

strugee

speaking of good stories:

ibiblio.org/harris/500milemail.html

mikeserv

@slm My name really is Mike, by the way.

slm

Mar 14, 2014 03:08

$ more somefile.txt
echo "hi mike"
echo "sam sourced this"

$ more somescript.bash
#!/bin/bash

. somefile.txt

OK>?

franike

mikeserv

That wont work.,

. ./somefile.txt

slm

pretend I'm your math teacher, show your work

terdon

@mikeserv why not? He just showed you the strace output of exactly how that works. Incidentally, the same output clearly demonstrated that one is executed and the other is read as a text file.

casey

casey@convect ~ % cat test3.sh
#!/this/path is garbage.
print This statement is being executed
casey@convect ~ % . ./test3.sh
This statement is being executed

slm

He's not going to buy it

casey

Mar 14, 2014 03:11

casey@convect ~ % ./test3.sh
zsh: ./test3.sh: bad interpreter: /this/path: no such file or directory

slm

come on man put it together

Did we hit 88 miles per hour in the Delorian?

@terdon - still wanting that flame war?

terdon

@slm yeah, see, I'm prescient!

casey

casey@convect ~ % cat test4.sh
#!/usr/bin/python2 -V
print test
casey@convect ~ % . ./test4.sh
test
casey@convect ~ % ./test4.sh
Python 2.7.5

Braiam

@casey just... wow

terdon

I always knew I was special. My mom told me when I was but a lad.

@casey very nice!

mikeserv

Mar 14, 2014 03:15

echo "current shell $0" ; printf %s\\n '#!/usr/bin/dash' 'echo script shell '\$0 >~/somefile.txt
; . ~/somefile.txt

current shell -/usr/bin/zsh
script shell /home/mikeserv/somefile.txt

casey

@Braiam @terdon thanks. I had a vision...

mikeserv

@casey This didnt work because . is not ./

@Braiam ./test3.sh That one I mean

casey

@mikeserv no, it worked exactly as it should have

terdon

@mikeserv he used ./ to execute the script and . to source it

mikeserv

@casey Not according to this: casey@convect ~ % ./test3.sh

@terdon The directory link ./ is not the shell builtin .

Braiam

Mar 14, 2014 03:19

@mikeserv just how you think he should do it?

casey

test3 and test4 demonstrate the hashbang is ignored because the shell is interpreting the contents itself and not spawning the interpreter as another process

and I did both . and ./ to show the difference

mikeserv

@casey . ./

Oh, well, like I said I only think that can be done. Mine worked though - at least for $0.

terdon

@mikeserv em, yes, exactly. But he just used ./ when executing, note that he wrote . ./foo.sh

@mikeserv but that's exactly what he did!

casey

. ./file <- . is the builtin, and ./file is a relative path to a filename

mikeserv

Ok, I was looking at my shell doing the other thing and just saw a zsh error.

Besides I think that's implementation dependent anyway, but I'm not sure.

casey

Mar 14, 2014 03:21

here it is again, both ways together

casey@convect ~ % . ./test3.sh
This statement is being executed
casey@convect ~ % ./test3.sh
zsh: ./test3.sh: bad interpreter: /this/path: no such file or directory

mikeserv

@casey exactly that.

terdon

@mikeserv give us some credit "dude". You'd think the regulars on a site like this might just be aware of what ./ means!

mikeserv

@casey Ok, I get it now. So it didn't take its hash bang. I didn't, til I read it.

casey

yes, because it is not a valid script, but it does contain some valid statements that zsh can parse

which is why sourcing it works

slm

sourcing views it as a comment

casey

Mar 14, 2014 03:23

exactly

mikeserv

I dunno, it only came up because slm used this as proof it didn't work. $ more somescript.bash
#!/bin/bash

. somefile.txt
OK>?
franike

casey

which i thought the python demonstrated quite well

slm

read up on how shebang works too

Shebang (Unix)

In computing, a shebang (also called a sha-bang, hashbang, pound-bang, hash-exclam,), is the character sequence consisting of the characters number sign and exclamation mark (that is, "#!") at the beginning of a script. Under Unix-like operating systems, when a script with a shebang is run as a program, the program loader parses the rest of the script's initial line as an interpreter directive; the specified interpreter program is run instead, passing to it as an argument the path that was initially used when attempting to run the script. For example, if a script is named with the path "...

terdon

Yeah, what was that about "No hash bang, and you might not have a new process at all."?

casey

without a hashbang you should get a new process but the same interpreter

slm

Mar 14, 2014 03:26

the hashbang is a magic number

casey

yep

Braiam

PSA: Shog said what is an answer:

12

Q: Your answer is in another castle: when is an answer not an answer?

I think we can all agree, this sucks: If you've been around a little while, you've probably encountered hundreds of answers like this in various forums, some of them even marked as "The Answer" by well-meaning* forum admins looking to close a thread. We could try to enumerate the commonly-obse...

mikeserv

Ok, now some others need the arrow.

slm

The shebang is actually a human-readable instance of a magic number in the executable file, the magic byte string being 0x23 0x21, the two-character encoding in ASCII of #!. This magic number is detected by the "exec" family of functions, which determine whether an image file is a script or an executable binary.

casey

@mikeserv scrolling back that far is pretty hard

mikeserv

Mar 14, 2014 03:29

@casey It is on the tv, yeah.

Sorry

But I didn't know if I was being asked a question or if you guys were talking to each other.

casey

@mikeserv I think its safe to say the validity of that statement was called into question.

slm

"which determine whether an image file is a script or an executable binary." This last bit would seem to imply that a file with commands in it is neither

mikeserv

@casey Which statement? That . might interpret a hash bang depending on implementation?

I think so too.

casey

No, the "No hash bang, and you might not have a new process at all."? statement

see this:

casey@convect ~ $ cat test5.sh
echo pid = $BASHPID
casey@convect ~ $ echo $BASHPID
28589
casey@convect ~ $ . ./test5.sh
pid = 28589
casey@convect ~ $ ./test5.sh
pid = 28915

no hashbang, but executing it (not sourcing it) results in a subshell in a new process.

mikeserv

Did I say that? Yeah, I think that's wrong. But sourcing it does execute it. And all the sourced script needs to do is exec out, or if it wants a subshell it just ( asks ) for one.

casey

Mar 14, 2014 03:38

@mikeserv . by definition cannot interpret a hashbang, because to do so requires spawning a process via exec and then you are no longer executing the following statements in the current shell

I would be very surprised to see another (non POSIX) implementation of source

mikeserv

In any case it's definitely executed - that's it's definition.

terdon

33 mins ago, by mikeserv

@slm I consider that thinking fallacious, because the shell does that, probably, but it's not guaranteed and is usually a result of the hash bang. No hash bang, and you might not have a new process at all.

mikeserv

NAME

dot - execute commands in the current environment

casey

no one is arguing that as far as I'm aware?

mikeserv

What was the next statement I made?

That was what I spent first 30 minutes here debating.

slm

Mar 14, 2014 03:40

what are you arguing about now?

casey

Anyway, my tests stand on their own... interpret them as you wish

slm

i left to help other ppl w/ questions

terdon

@slm same

slm

this is turning into a waste of time

ask a Q on the site if you have one framike

terdon

Changing the subject, I've been playing around on an Ubuntu VM this week. Does this look familiar to anyone?

/dev/chat

Participants