simple popen question

[Jim Benson]

Hi,

I use popen to run a binary executable.
A code snippit is below.
This part runs fine. I use readline()
to catch and print output from the binary
to the screen. The system obviously buffers
things. i.e. readline doesn't return after every
line of output from the executable.
Is there an easy way to turn off the buffering?
I tried adding the extra 'r' and a small bufsize
to the popen...no difference.

iFd = os.popen(self.sCmd + ' ' + sArgs)
# Run sCmd
while True:
line = iFd.readline()
if line == '':
# EOF found...break out.
break;

print '%s' % line[:-1]

iRet = iFd.close()

if (iRet != None):

print 'ERROR: error message'


Thanks,

Jim

 

[Cameron Laird]

Hi,

I use popen to run a binary executable.
A code snippit is below.
This part runs fine. I use readline()
to catch and print output from the binary
to the screen. The system obviously buffers
things. i.e. readline doesn't return after every
line of output from the executable.
Is there an easy way to turn off the buffering?
I tried adding the extra 'r' and a small bufsize
to the popen...no difference.

iFd = os.popen(self.sCmd + ' ' + sArgs)

# Run sCmd
while True:
line = iFd.readline()
if line == '':
# EOF found...break out.
break;

print '%s' % line[:-1]

iRet = iFd.close()

if (iRet != None):

print 'ERROR: error message'

.
.
.
In general, no; the reader doesn't control the buffering, the writer does.

But there are several tangential issues raised here. Most crucially: do
you control the (source of the) "binary executable"? If you do, what I
think you'll find most satisfying is to recompile it with buffering disabled,
at least on newlines.