CODEWITHSUNDEEP
pythonbashshellzsh
Sindhu S
Sindhu S

Reputation: 1012

Passing arguments from shell to embedded Python scripts

I wrote a shell function, intended to be compatible with both zsh and bash:

py () { python -c 'print($1)'; }

but when i use py hello, I get an error from the Python interpreter:

➜  ~  py hello
  File "<string>", line 1
    print($1)
          ^
SyntaxError: invalid syntax

What am I doing wrong? Thanks!

Upvotes: 0

Views: 330

Answers (1)

Charles Duffy
Charles Duffy

Reputation: 295687

Don't use string substitution at all -- that way lies (a cousin of) Bobby Tables. Instead, pass arguments out-of-band:

py() { python -c 'import sys; print sys.argv[1]' "$@"; }
py hello

To demonstrate why the other approach is dangerous:

py() { python -c "print('${1}')"; }
py "hello' + str(__import__('os').system('touch /tmp/broke-your-security')) + '"

When run, this code creates a file /tmp/broke-your-security. Consider what would happen if that command instead involved rm -rf, or curl | sh to pull down a rootkit.

Upvotes: 2

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