lua run a shell command with parameters doesn't work

Question

I am trying to execute a command from lua script. The command is to simply run a python script named "sha_compare.py" of which receives 3 arguments where two of them are variables from the lua script - dady_data and sha:

local method = ngx.var.request_method
local headers = ngx.req.get_headers()

if method == "POST" then
   ngx.req.read_body()
   local body_data = ngx.req.get_body_data()
   local sha = headers['X-Hub-Signature-256']
   ngx.print(os.execute("python3 sha_compare.py"..sha..body_data))
else

The script fails because of the way I call the arguments. The actual command if I would have ran it from cmd would have been something like:

python3 python3 sha_compare.py sha256=ffs8df aaaaa

Please tell me how should I change my code to call the python script with 3 vars properly.

If it is not possible or hard to implement, please let me know how can I call a .sh script which will receive those 3 params.

What's inside body_data? Does it contain characters which are "magical" for shell? — Egor Skriptunoff
– Egor Skriptunoff, Commented Feb 28, 2021 at 18:34

glenn jackman · Accepted Answer · 2021-02-28 14:12:23Z

1

You're not providing spaces between the arguments: you're trying to execute

python3 sha_compare.pysha256=ffs8dfaaaaa

Do this:

os.execute("python3 sha_compare.py "..sha.." "..body_data)

It's often easier to build the command up as a table, and the concat it for execution:

local cmd = { 'python3', 'sha_compare.py', sha, body_data }
os.execute(table.concat(cmd, " "))

answered Feb 28, 2021 at 14:12

glenn jackman

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4 Comments

jrz Over a year ago

os.execute("python3 sha_compare.py "..sha.." "..body_data) doesn't work, won't even compile. I get error server 500. And the table option returns 512...

jrz Over a year ago

I added a full path to the script name. Now getting error 256.

glenn jackman Over a year ago

Does body_data contains spaces and/or quotes? If so you'll have to make sure the value is properly quoted for the shell.

jrz Over a year ago

Can you please take a look over this thread as well? This is critical for me. Thanks. stackoverflow.com/questions/66527896/…

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