newlispfanclub.alh.net

Hi,
I'm trying porting from python to newlisp (of course) but python has possibility of assigning stderr output to a pipe when starting a process
eg from chatsniff1.0.py - http://chatsniff.sourceforge.net/
pipe = Popen('tethereal -i '+str(gDevices.index(gCurrentDevice) + 1)+' -l -V -R \"aim || ymsg || msnms || jabber\"', bufsize = 1, cwd = path, shell=True, stdin=PIPE, stdout=PIPE, stderr=PIPE, universal_newlines = True)

while (process in newlisp syntax is : (process str-command int-pipe-in int-pipe-out [int-win32-option])
i.e. only stdin stdout directable to pipes.
The code in nl-filesys.c is:

CELL * p_process(CELL * params)
{
char * command;
int forkResult;
int inpipe = 0, outpipe = 0;

params = getString(params, &command);
if(params != nilCell)
{
params = getInteger(params, (UINT*)&inpipe);
getInteger(params, (UINT *)&outpipe);
}

if((forkResult = fork()) == -1)
return(nilCell);
if(forkResult == 0)
{
/* redirect stdin and stdout to pipe handles */
if(inpipe)
{
close(STDIN_FILENO);
if(dup2(inpipe, STDIN_FILENO) == -1) exit(0);
close(inpipe);
}
if(outpipe)
{
close(STDOUT_FILENO);
if(dup2(outpipe, STDOUT_FILENO) == -1) exit(0);
close(outpipe);
}

system(command);
exit(0);
}
could another option after [int-win32-option] be [int-pipe-err]
and newlisp do STDERR_FILENO to pipe?
Or is this not recommended?

Is there another way? - I see in
return value thread ( http://www.alh.net/newlisp/phpbb/viewtopic.php?t=789 ) that stderr can be handled from exec
Lutz:
> (exec "ls *.abc 2>&1")
("ls: *.abc: No such file or directory")
>
The 2>&1 spec tell ls to redirect error output to stdout.

but don't know enough about system() to know if that approach is possible for (process.

Any tips?

Nigel

Hello Nigel,

Did you try a combination of switching (device [int] )
to input/output/erro or pipe?
That could be a workaround, i did not test it though..

regards, Norman.

Hi Norman,
I'm not sure what you mean by switching?

I've experimented with redirecting 2>&1 with a single line command and it works:
> (process "ls *.abc 2>&1" procin procout)
11118
> (read-line myin)
"ls: *.abc: No such file or directory"
>

Looking more at system() it does start a shell for the process so I'll use the 2>&1 approach.
Longer term newlisp might like to look at having optional capture of stderr to its own pipe (Lutz?).
full eg from python
pipe = Popen('tethereal -i '+str(gDevices.index(gCurrentDevice) + 1)+' -l -V -R \"aim || ymsg || msnms || jabber\"', bufsize = 1, cwd = path, shell=True, stdin=PIPE, stdout=PIPE, stderr=PIPE, universal_newlines = True)
global maintetherealpid
maintetherealpid = pipe.pid
pipe.stdin.close()
f = pipe.stdout
e = pipe.stderr
...

Nigel

Currently only in Win32 stderr is redirected to the stdout pipe. On Linux/UNIX you can use the stderr redirection: 2>&1 on 'process' and 'exec'.

Yes, perhaps in the future an optional switch, although 2>&1 works already.

Lutz

Hi Lutz,
I agree it's not a priority. However, it would allow easier recognition and handling of error or warning messages.

Regards
Nigel

I have added an optiion for 8.7.5

Lutz

Fantastic! Thank you Lutz, it will make my parsing of stdout much easier with stderr going elsewhere.

Regards
Nigel