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问题:
This question already has an answer here:
I'd like to use subprocess on the following line:
convert ../loxie-orig.png bmp:- | mkbitmap -f 2 -s 2 -t 0.48 | potrace -t 5 --progress -s -o ../DSC00232.svg
I found thank to other posts the subprocess documentation but in the example we use only twice pipe.
So, I try for two of the three commands and it works
p1 = subprocess.Popen(['convert', fileIn, 'bmp:-'], stdout=subprocess.PIPE) # p2 = subprocess.Popen(['mkbitmap', '-f', '2', '-s', '2', '-t', '0.48'], stdout=subprocess.PIPE) p3 = subprocess.Popen(['potrace', '-t' , '5', '-s' , '-o', fileOut], stdin=p1.stdout,stdout=subprocess.PIPE) p1.stdout.close() # Allow p1 to receive a SIGPIPE if p3 exits. output = p3.communicate()[0]
Can you help me for the third command?
Thank you very much.
回答1:
Just add a third command following the same example:
p1 = subprocess.Popen(['convert', fileIn, 'bmp:-'], stdout=subprocess.PIPE) p2 = subprocess.Popen(['mkbitmap', '-f', '2', '-s', '2', '-t', '0.48'], stdin=p1.stdout, stdout=subprocess.PIPE) p1.stdout.close() p3 = subprocess.Popen(['potrace', '-t' , '5', '-s' , '-o', fileOut], stdin=p2.stdout,stdout=subprocess.PIPE) p2.stdout.close() output = p3.communicate()[0]
回答2:
Use subprocess.Popen() with the option shell=True, and you can pass it your entire command as a single string.
回答3:
def runPipe(cmds): try: p1 = subprocess.Popen(cmds[0].split(' '), stdin = None, stdout = subprocess.PIPE, stderr = subprocess.PIPE) prev = p1 for cmd in cmds[1:]: p = subprocess.Popen(cmd.split(' '), stdin = prev.stdout, stdout = subprocess.PIPE, stderr = subprocess.PIPE) prev = p stdout, stderr = p.communicate() p.wait() returncode = p.returncode except Exception, e: stderr = str(e) returncode = -1 if returncode == 0: return (True, stdout.strip().split('\n')) else: return (False, stderr)
Then execute it like:
runPipe(['ls -1','head -n 2', 'head -n 1'])
