Joining stdout & stderr of subprocess ?

[robert]

when I run a command

myapp 2>&1
yet:

#!python
print os.popen("myapp 2>&1").read()

the stderr stuff comes all after the stdout stuff.
How can I get ahold of all the out and err joined synchronously in the
order, it is created ?
robert

[Duncan Booth]

robert wrote:

when I run a command

myapp 2>&1
[ I guess you meant to say here that the stdout, stderr output was
interleaved ]
yet:

#!python
print os.popen("myapp 2>&1").read()

the stderr stuff comes all after the stdout stuff.
How can I get ahold of all the out and err joined synchronously in the
order, it is created ?

I think what is happening here is that in the first case the output is to a
terminal, so myapp doesn't buffer its output. In the second case the output
isn't going to a terminal so myapp is buffering it and only produces output
when the buffer is full. Probably there isn't sufficient stderr output to
force any out until myapp terminates, so you get it all at the end.

Probably the only way to get the output interleaved is to change myapp so
that it doesn't buffer its output or so it sends all of its output to a
single stream.

[Piet van Oostrum]

>>>>> robert <no*****@no-spam-no-spam.com> (R) wrote:

R> when I run a command R> myapp 2>&1
R> yet: R> #!python
R> print os.popen("myapp 2>&1").read() R> the stderr stuff comes all after the stdout stuff.
R> How can I get ahold of all the out and err joined synchronously in the
R> order, it is created ?

Make sure that myapp writes it synchronously. Probably myapp has it
buffered, so it writes out at the end of the run. It is not caused by
python.

--
Piet van Oostrum <pi**@cs.uu.nl>
URL: http://www.cs.uu.nl/~piet [PGP 8DAE142BE17999C4]
Private email: pi**@vanoostrum.org

[Nick Craig-Wood]

robert <no*****@no-spam-no-spam.com> wrote:

when I run a command

myapp 2>&1
Try

myapp 2>&1 | cat

and see what you get. You should get the same output as the python.
#!python
print os.popen("myapp 2>&1").read()

the stderr stuff comes all after the stdout stuff.
How can I get ahold of all the out and err joined synchronously in the
order, it is created ?

You need to either

1) change myapp to fflush() more often

2) investigate the python pty module to fool the app into thinking it
is talking to a terminal

--
Nick Craig-Wood <ni**@craig-wood.com> -- http://www.craig-wood.com/nick

[Stephane Chazelas]

On Fri, 21 Apr 2006 09:30:06 -0500, Nick Craig-Wood wrote:

robert <no*****@no-spam-no-spam.com> wrote:

when I run a command

myapp 2>&1

Try

myapp 2>&1 | cat

and see what you get. You should get the same output as the python.

#!python
print os.popen("myapp 2>&1").read()

the stderr stuff comes all after the stdout stuff.
How can I get ahold of all the out and err joined synchronously in the
order, it is created ?

You need to either

1) change myapp to fflush() more often

2) investigate the python pty module to fool the app into thinking it
is talking to a terminal

[...]

3) write a LD_PRELOAD wrapper that turns isatty() into a
function that returns true if its arg is 1.

4) perl -pi -e 's/isatty/fchdir/g' myapp
(might not work ;).
--
Stephane