pipes and commands

[Gregor Zych]

Hi!
How can I get many commands connected with pipes executed. I try

startexe = 'gs -q -dNOPAUSE -sDEVICE=pbmraw -r600x600 -sOutputFile=- '+pfad+'/'+name+'.eps quit.ps | pnmcut 610 982 4023 5483 | pnmtotiff - > '+pfad+'/'+name+'.tif'
os.system(startexe)

but the system just waits for ever until I interrupt it, although it
gets the final file written correctly.
os.popen() seems to make my system unusable 'cos it slurps the generated 
file und these pictures are HUGE. Any hints are welcome.
Linux 2.2.11 python 1.5.2
Ciao
	Gregor