Pipe result from subprocess to unix sort

问题:

I am calling a perl script on an external txt files from python, and printing the output to an outfile. But instead I want to pipe the output to unix's sort. Right now I am not piping, but are writing the output from the perl program first, then doing by combining my code under, and this stackoverflow answer.

import subprocess
import sys
import os

for file in os.listdir("."):

    with open(file + ".out", 'w') as outfile:
        p = subprocess.Popen(["perl", "pydyn.pl", file], stdout=outfile)
        p.wait()

回答1:

Since you asked the question in python you can also pipe the result

p = subprocess.Popen("perl pydyn.pl %s | sort" % file, stdout=outfile,shell=True) 

but for this you're gonna have to make it shell=True which is not a good practice

Here's one way without making it shell=True

  p = subprocess.Popen(["perl", "pydyn.pl", file], stdout=subprocess.PIPE)
  output = subprocess.check_output(['sort'], stdin=p.stdout,stdout=outfile)
  p.wait()

回答2:

To emulate the shell pipeline:

#!/usr/bin/env python
import pipes
import subprocess

pipeline = "perl pydyn.pl {f} | sort >{f}.out".format(f=pipes.quote(filename))
subprocess.check_call(pipeline, shell=True)

without invoking the shell in Python:

#!/usr/bin/env python
from subprocess import Popen, PIPE

perl = Popen(['perl', 'pydyn.pl', filename], stdout=PIPE)
with perl.stdout, open(filename+'.out', 'wb', 0) as outfile:
    sort = Popen(['sort'], stdin=perl.stdout, stdout=outfile)
perl.wait() # wait for perl to finish
rc = sort.wait() # wait for `sort`, get exit status

回答3:

Just use bash. Using python just adds a level of complexity you don't need.

for file in $( ls); 
do 
    perl pydyn.pl $file | sort
done

Above is a quick and dirty example, a better alternative in terms of parsing is the following:

ls | while read file; do perl pydyn.pl "$file" | sort; done