Escaping quotes in bash command using subprocess call and shlex

Question

I am executing bash command using python's subprocess.call(). I am taking user input as an argument to my command like below.

my_command = 'command -option1 {0} -option2 {1}'.format(arg1, arg2)

Here arg1 and arg2 are user inputs but the problem is user input can have quotes and spaces so I want to surround arguments by double quotes like this.

my_command = 'command -option1 "{0}" -option2 "{1}"'.format(arg1, arg2)

Since I have no control over user input, input can contains double quotes or single quotes. Hence I am replacing input with following escape sequence.

arg1 = arg1.replace('"', '\"').replace("'", "\'")
arg2 = arg2.replace('"', '\"').replace("'", "\'")
my_command = 'command -option1 "{0}" -option2 "{1}"'.format(arg1, arg2)

All looks good to me but when I execute command I get following error.

subprocess.call(shlex.split(my_command))

File "/usr/lib/python2.6/shlex.py", line 279, in split return list(lex)

File "/usr/lib/python2.6/shlex.py", line 269, in next token = self.get_token()

File "/usr/lib/python2.6/shlex.py", line 96, in get_token raw = self.read_token() File "/usr/lib/python2.6/shlex.py", line 172, in read_token

raise ValueError, "No closing quotation"

ValueError: No closing quotation

How can I deal with it ?

Edit : I want to preserve those quotes and spaces in bash command.

Unrelated: `shlex` is not very sophisticated. [It may break easily: `r'echo "\$x"'`](http://stackoverflow.com/questions/28468807/python-executing-a-shell-command#comment45287698_28468860). It is useful during development, to create an initial `args` list from an existing example command-line. — jfs, Mar 03 '16 at 12:07

score 3 · Accepted Answer · answered Mar 03 '16 at 03:36

3

Don't deal with quotation marks, spaces, etc. Just use a list:

my_command = ["command", "-option1", arg1, "-option2", arg2]
subprocess.call(my_command)

answered Mar 03 '16 at 03:36

zondo

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This approach wont work because input can have spaces and split will be based on spaces. – Ashok Kumar Mar 03 '16 at 03:54
My solution doesn't use `split`. – zondo Mar 03 '16 at 03:57

score 0 · Answer 2 · answered Mar 03 '16 at 03:35

0

You are not escaping quotes in your current code as \" is simply equal to ". You should use double escapes to escape the backslash (\) character:

arg1 = arg1.replace('"', '\\"').replace("'", "\\'")
arg2 = arg2.replace('"', '\\"').replace("'", "\\'")

answered Mar 03 '16 at 03:35

Selcuk

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Thanks Sekcuk But problem is I want to preserve those quotes and spaces. – Ashok Kumar Mar 03 '16 at 03:44
@AshokKumar That's why you should escape them using the method I suggested. – Selcuk Mar 03 '16 at 03:50

Escaping quotes in bash command using subprocess call and shlex

2 Answers2