[hashcash] parallel hashcash -- Python script

  • From: Hubert Chan <hubert@xxxxxxxxx>
  • To: hashcash@xxxxxxxxxxxxx
  • Date: Thu, 10 Mar 2005 16:01:38 -0500

I've ported my parallel hashcash program to Python -- since it's just a
wrapper around the normal hashcash program.  This version should be
ready for general consumption.  The script reads the stamp from its
children via a pipe, so the multiple instances won't step on each other.


# hashfork.py
# by Hubert Chan, March 2005
# This file is hereby placed in the public domain.

import os
import signal
import sys

if len(sys.argv) < 3:
    print "Run multiple instances of hashcash in parallel"
    print "usage:"
    print " ", sys.argv[0], "<processes> <hashcash command line arguments>"
    print "    <processes> is the number of hashcash processes to start"
    print "    <hashcash command line arguments> is the command line argumens 
to pass to"
    print "        hashcash.  Note that the -m option will be automatically 
added, and"
    print "        so does not need to be specified."
    print "Note: you MUST specify a resource on the command line."
    sys.exit ()

NUM_PROCS = int (sys.argv[1])

del (sys.argv[0:2])
sys.argv.insert(0, "hashcash")
sys.argv.insert(1, "-m")

children = [ ]
pipes = [ ]

for i in range (NUM_PROCS):
    pipe = os.pipe () # create a pipe to communicate with the child
    pid = os.fork ()
    if pid:
        # parent
        children.append (pid)
        os.close (pipe[1]) # close the write end of the pipe
        pipes.append (os.fdopen (pipe[0]))
#        print "process", pid, "started"
        # child
        os.close (pipe[0]) # close the read end of the pipe
        os.dup2 (pipe[1], 1) # redirect stdout to the pipe
        os.close (pipe[1])
        os.execvp ("hashcash", sys.argv)

status = os.wait ()

#print "process", status[0], "exited.\nkilling all children."

for i in range (NUM_PROCS):
#    print children[i]
    if children[i] == status[0]:
        print (pipes[i].readline ()),
        os.kill (children[i], signal.SIGKILL)
    except OSError: # kill raises an OSError when the process already exited
Note that this script will only work on UNIX systems because it uses the
wait function, which is only available on UNIX.  If anyone knows how to
do the equivalent in Windows, let me know.  I think execvp is only
available under UNIX as well (but that can be easily gotten around by
hard-coding the path to hashcash).

Hubert Chan <hubert@xxxxxxxxx> - http://www.uhoreg.ca/
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