Why aren't there quotes in sys.argv when they were used at the command line?

user_631199 0
Viewed 1574

Is this a bug?

#!/usr/bin/env python3.6
# filename: tmp.py
import sys

print(sys.argv)

Invoked:

python tmp.py find . -name '*.py'

Actual output:

['tmp.py', 'find', '.', '-name', '*.py']

Expected output:

['tmp.py', 'find', '.', '-name', "'*.py'"]

Note the lack of quotations within the actual output.

shell python command-line-arguments
2 Answers

no, because your shell removes the quotes before passing the argument to python (else it would expand the *.py wildcard)

To get what you want you'd need:

python tmp.py find -name "'*.py'"

Note that this behaviour is shell dependent. On windows, since single quotes have no particular meaning, passing '*.py', you would get:

['tmp.py', 'find', '.', '-name', "'*.py'"]

Also note that quote-protected wildcards have no real interest on the python side, since you'd need to strip the quotes to be able to evaluate them with glob.glob

user_64515730

The shell is responsible for breaking down the command it's running into a list of C strings. Those strings are then passed to the program being run.

In the example:

python tmp.py find . -name '*.py'

...the argument list a correctly-implemented shell will generate for the argv element of the execve syscall would look (in C syntax) like:

char[][]{ "python", "tmp.py", "find", ".", "-name", "*.py", NULL }

When Python runs, it doesn't know what the original command was: It has no way of knowing if you typed '*.py' or \*.py or any other thing; it only sees the argument list the shell handed off to the operating system.

user_141220
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