display output of a command line utility in GUI

[NeillHog]

The problem in a nutshell – I am writing a GUI wrapper for a command line utility (GPSBabel) and want to show the output of the command line on an error. I am a very inexperienced Python programmer.

Calling the program from the command line as follows

neill@NeillsPC:$ gpsbabel -igarmin -f/dev/ttyS1 -o zzz -F/home/neill/temp

produces the following output to the screen
[ERROR] GPS_Packet_Read: Timeout. No data received.
GARMIN:Can't init /dev/ttyS1
This is what I would like to show the user of the GUI but I can find no way of doing so.

I though that sending the output to the file would be a good start. From the command line I changed the command to

gpsbabel -igarmin -f/dev/ttyS1 -o zzz -F/home/neill/temp > /home/neill/temp/err.log  2>&1

which sent everything to the file err.log as expected.

In my program I call GPSBabel with

result = os.spawnlp(os.P_WAIT, 'gpsbabel', 'gpsbabel', dataString, inputFormatStr, inputFileStr, outputFormatStr, outputFileStr)

and can not see how to change that to be the same as my command line option.

I also tried

import sys
saveout = sys.stdout 
fsock = open('out.log', 'w')
sys.stdout = fsock

with stdout and stderr before calling the spawn.

Now I am stumped. Please help me some one even if only by telling me that it is impossible.

Thanks!
Neill

[strider1551]

I want to show the output of the command line on an error.

Personally, I prefer to use the subprocess module.

import subprocess
process = subprocess.Popen("your command here", shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE, bufsize=0)
print process.stdout.read()
print process.stderr.read()

[NeillHog]

Thank you for that.
I just had a quick look at the code and it looks complicated.
I will get back to you in a few hours/days once I have worked out what I need to do.
As I said "thanks"

Neill!

[NeillHog]

It works

# the command line to call
progString = 'gpsbabel ' + dataString + inputFormatStr + ' ' + inputFileStr + ' ' + \
outputFormatStr + ' ' + outputFileStr				
# Information what we are calling
self.textEditInfo.append('Command: ' + progString + '\n')
# Call GPSBabel
extProcess = subprocess.Popen(progString, shell=True, stderr=subprocess.PIPE)
#  and read any errors
errStr = extProcess.stderr.read()
self.textEditInfo.append('GPSBabel says: ' + errStr + '\n')

Thank you so much for your simple but very effective tip.
I found spawn starnge but subprocess acted exactly as I expected.

What held me up for an hour was that all the little strings that go to make up progString are input from lineEdits and I was using lineEdit.text() which would not work - lineEdit.text().ascii() would though.

Thanks!
Neill