maximum command line parameter length? 命令行参数可以有多长？

#how long can a command line parameter have?
#
# Directly answer is 8196 on Window7(not sure about other platform)
#
#It’s easy to write a script to repro it:
#1. In one script, output the parameter it got, say script#1
#2. In another script, recursively execute script#1 and increase parameter step by step,
#   capture the output, see if you have the same with the parameter you give
#
# Usage: python test2.py
#        then you got the result
#        (if it's 10000, then adjust "end" variable below)
#
#--- test.py ---
import sys
print sys.argv[1]

#--- test2.py ---
import sys,os
param = 'a'
start = 0
end =  10000
while start < end: #binary search to speed up
    mid = (start + end) / 2
    param = 'a' * mid
    cmdline = 'test.py ' + param
    out = os.popen(cmdline).read().rstrip()
    if param == out:
        start = mid + 1
    else:
        end = mid - 1
    print len(param)
print "\nMax Command Line Length=", start

#What I got on Window7 is: 8153
#  considering cmd.exe starts with "C:\\Windows\\system32\\cmd.exe /c test.py "
#  then the maximum is about 8196