如何使用python 2在os.system命令中转义/使用单引号？

Question

i have built a small script that runs a simple shell utility called imapsync, with a bunch of variables taken from a dictionary, the command is as follows:

os.system("imapsync --host1 %s --user1 %s --password1 '%s' --host2 %s --user2 %s --password2 '%s' --ssl1 --no-modulesversion --ssl2" % (fromHost, emails, passwords, toHost, emails, passwords))

the deal is that passwords often contain special characters, example: djDJS*^%%%^&)

this imapsync tool allows such characters if enclosed in single quotes: 'djDJS*^%%%^&)'

what I am trying to achieve is post the single quotes in the command, itself.. I tried "'", backquotes - ``, escaped quotes - \\'\\', enclosing the command in single quotes, nothing worked thus far

Answer 1

After looking through the documentation of imapsync, I found the recommendation to enclose passwords in double quotes within single quotes to avoid common problems .

Since you already start the string with double quotes, you have to escape the double quotes around your password with a backslash \\" .

There are also two things you could do to make your code even better. First, you can use .format syntax for string formatting instead of the old % syntax.

Second replace os.system with subprocess.Popen . This allows you to split your command string into a list of all arguments, which looks more clear.

Your new code would look like

import subprocess

args = [
  "imapsync",
  "--host1",
  fromHost,
  "--user1",
  emails,
  "--password1",
  "'\"{}\"'".format(passwords),
  "--host2",
  toHost,
  "--user2",
  emails,
  "--password2",
  "'\"{}\"'".format(passwords),
  "--ssl1",
  "--no-modulesversion",
  "--ssl2"
]

p = subprocess.Popen(args, stdout=subprocess.PIPE)

output = p.communicate()[0]

print(output)

In this example Popen.communicate is used to gather the output of the imapsync command as a string. The communicate method returns a tuple with the outputs of the subprocess to stdout and stderr streams.

If you also want to read the output to stderr from the subprocess, change the code as following:

p = subprocess.Popen(args, stdout=subprocess.PIPE, stderr=subprocess.PIPE)

output, errors = p.communicate()

print(output)
print(errors)

Answer 2

The best format for passing string parameters in Python is to use the format string method. You could do something like this:

line_command = "imapsync --host1 {fromHost} --user1 {emails} --password1 '\"{passwords}\"' --host2 {toHost} --user2 {emails} --password2 '\"{passwords}\"' --ssl1 --no-modulesversion --ssl2".format(fromHost=fromHost, emails=emails, passwords=passwords, toHost=toHost)
os.system(line_command)