Question

I’m writing to a file for another program (gnuplot) to use as input.

g = open('test.gnuplot', 'w')
g.write("[snip]")
g.close()

os.system("sleep 1")
os.system("gnuplot test.gnuplot")

If I omit the sleep 1 gnuplot generates a mangled file – seemingly because the file I just wrote isn’t “ready” yet (if I’m wrong please tell me what the real reason is).

I’m guessing there is a more elegant way to wait for the file to be ready for reading, what is it?

Answer 1

Try this:

g = open('test.gnuplot', 'w')
g.write("[snip]")
g.flush()
os.fsync(g.fileno()) 
os.system("gnuplot test.gnuplot")

And take away the os.system("sleep 1"). I think the buffer is not yet written to the file. See the python fsync docs.