Re: 'tty' output on kFreeBSD, etc. within sbuild

2014-01-06 Thread Ian Jackson 
Alastair McKinstry writes ('tty' output on kFreeBSD, etc. within sbuild):
 Can anyone answer the following question which is puzzling me;
 I have a piece of csh code which gets called during the build of a package
 i'm maintaining. it does the following:
 
 echo useful information  /dev/tty
 
 within the script. (stdout, stderr being redirected, I think).

Others have explained why you shouldn't do this.

If you want to bypass some redirection in the rest of your package's
build system, you could stash a copy of stderr in fd 3 or 5 or
something (eg, in the rules file, with 32), and then write to fd 5.

But perhaps more information would enable us to give better advice.

Thanks,
Ian.


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Re: 'tty' output on kFreeBSD, etc. within sbuild

2014-01-06 Thread Alastair McKinstry 
On 06/01/2014 12:39, Ian Jackson wrote:
 Alastair McKinstry writes ('tty' output on kFreeBSD, etc. within sbuild):
 Can anyone answer the following question which is puzzling me;
 I have a piece of csh code which gets called during the build of a package
 i'm maintaining. it does the following:

 echo useful information  /dev/tty

 within the script. (stdout, stderr being redirected, I think).
 Others have explained why you shouldn't do this.

 If you want to bypass some redirection in the rest of your package's
 build system, you could stash a copy of stderr in fd 3 or 5 or
 something (eg, in the rules file, with 32), and then write to fd 5.

 But perhaps more information would enable us to give better advice.

 Thanks,
 Ian.


Thanks, I've been able to adapt the build scripts so it is not necessary;
they just output to stdout.

Regards
Alastair


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http://blog.sceal.ie

Anyone who believes exponential growth can go on forever in a finite world
is either a madman or an economist - Kenneth Boulter, Economist.


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Re: 'tty' output on kFreeBSD, etc. within sbuild

2014-01-06 Thread Ian Jackson 
Alastair McKinstry writes (Re: 'tty' output on kFreeBSD, etc. within sbuild):
 On 06/01/2014 12:39, Ian Jackson wrote:
  But perhaps more information would enable us to give better advice.

 Thanks, I've been able to adapt the build scripts so it is not necessary;
 they just output to stdout.

Great, thanks.

Ian.


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'tty' output on kFreeBSD, etc. within sbuild

2014-01-03 Thread Alastair McKinstry 
Hi,

Can anyone answer the following question which is puzzling me;
I have a piece of csh code which gets called during the build of a package
i'm maintaining. it does the following:

echo useful information  /dev/tty

within the script. (stdout, stderr being redirected, I think).
This fails on kFreeBSD at least, so i've patched it to:

set ttyf=`tty`

...
echo useful information  $ttyf


This works on Linux, and on the command line for me on a kFreeBSD machine,
but under sbuild I get:

$ttyf: Ambiguous.
Unable to build Makefile - fix above errors and re-run.

Any ideas as to whats happening and what I should do about it?

Regards
Alastair

-- 
Alastair McKinstry  , alast...@sceal.ie , mckins...@debian.org  
http://diaspora.sceal.ie/u/amckinstry
Anyone who believes exponential growth can go on forever in a finite world is 
either a madman or an economist - Kenneth Boulter, Economist.

Re: 'tty' output on kFreeBSD, etc. within sbuild

2014-01-03 Thread Roger Leigh 
On Fri, Jan 03, 2014 at 06:51:08PM +, Alastair McKinstry wrote:
 Can anyone answer the following question which is puzzling me;
 I have a piece of csh code which gets called during the build of a package
 i'm maintaining. it does the following:
 
 echo useful information  /dev/tty
 
 within the script. (stdout, stderr being redirected, I think).
 This fails on kFreeBSD at least, so i've patched it to:
 
 set ttyf=`tty`
 
 ...
 echo useful information  $ttyf
 
 
 This works on Linux, and on the command line for me on a kFreeBSD machine,
 but under sbuild I get:
 
 $ttyf: Ambiguous.
 Unable to build Makefile - fix above errors and re-run.
 
 Any ideas as to whats happening and what I should do about it?

You aren't guaranteed to have a controlling terminal, particularly when
run via buildd.  So while stdin/out/err are all connected and
functional, they are either null (stdin) or pipes (out/err).  If you
need to output anything, then just use stdout/err as appropriate and it
will be logged, but /dev/tty may well be unavailable.  I would
recommend not using `tty` or doing any IO on /dev/tty since in all
likelihood isatty/ttyname(_r) will most likely return ENOTTY and any
IO on /dev/tty will simply fail.

We have looked at using ptys in the past for running the builds in
order to guarantee a tty, but decided against it.  Too many programs
make the assumption that they are interactive and freeze the build
waiting on IO that never happens and then block forever.  There may
well have been other considerations I don't recall offhand e.g.
relating to job control.


Regards,
Roger

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Re: 'tty' output on kFreeBSD, etc. within sbuild

2014-01-03 Thread Colin Watson 
On Fri, Jan 03, 2014 at 07:12:51PM +, Roger Leigh wrote:
 You aren't guaranteed to have a controlling terminal, particularly when
 run via buildd.  So while stdin/out/err are all connected and
 functional, they are either null (stdin) or pipes (out/err).  If you
 need to output anything, then just use stdout/err as appropriate and it
 will be logged, but /dev/tty may well be unavailable.  I would
 recommend not using `tty` or doing any IO on /dev/tty since in all
 likelihood isatty/ttyname(_r) will most likely return ENOTTY and any
 IO on /dev/tty will simply fail.
 
 We have looked at using ptys in the past for running the builds in
 order to guarantee a tty, but decided against it.  Too many programs
 make the assumption that they are interactive and freeze the build
 waiting on IO that never happens and then block forever.  There may
 well have been other considerations I don't recall offhand e.g.
 relating to job control.

There are some limited situations (e.g. test suites) where it can come
in handy.  For these, I'd recommend lifting the debian/script.py I wrote
from the python2.7 source package, which gives you a pty in a way that's
known to work well within builds and writes output to a file.

-- 
Colin Watson   [cjwat...@debian.org]


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