I can't translate a terminal command to System.cmd/3

Samuel-88

Hello all,

I’m trying to run the following terminal command inside Elixir:

curl -X POST http://localhost:4004/api/converter -H "Content-Type: application/json" -d '{"html": "a", "organization_id": "9213898231sadasd000"}'

It executes perfectly in the terminal, but when I try it in iex like this:

System.cmd("curl", ~w[-X POST http://localhost:4004/api/converter -H "Content-Type: application/json" -d '{"html": "a", "organization_id": "9213898231sadasd000"}'])

I get a bad request. I already read the documentantion and looked how different people did it, but I can’t make it work. Does anyone have any idea what I’m doing wrong?

Thanks!

6 comments

#troubleshooting #system

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2022-03-30 17:26:44 UTC

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al2o3cr

As noted in this thread from last week:

~w() will not do what you want if arguments have spaces in them:

~w(-H "Content-Type: application/json")

is a list with three elements:

["-H", "\"Content-Type:", "application/json\""]

Post #1

Samuel-88

Thanks a lot for your answer @al2o3cr.

Now I’m stuck at this:

System.cmd("curl", ["-X", "POST",  "http://localhost:4004/api/converter", "-H", "\"Content-Type:",  "application/json\"", "-d", "\"'{\"html":", "\"a\"", "\"organization_id\":", "\"9831298asa1231\"}'" ])

And the error is in this part: “"a"”

** (SyntaxError) iex:20:146: unexpected token: "\" (column 146, code point U+005C)

Any idea why?

Post #2

hauleth

You do not need the quotes inside quotes. These are just for shell, not for cURL

Post #3

Samuel-88

Thanks a lot for your answer. It stilll doesn’t work.

Post #4

l00ker

This should work

System.cmd("curl", [~s(http://localhost:4004/api/converter -H "Content-Type: application/json" -d '{"html": "a", "organization_id": "9213898231sadasd000"}')])

Post #5

al2o3cr

When you input a command in the shell, the shell is responsible for taking the whole string you typed:

curl -X POST http://localhost:4004/api/converter -H "Content-Type: application/json" -d '{"html": "a", "organization_id": "9213898231sadasd000"}'

and converting it to a command (curl) along with a series of options, separated by spaces. Most of the quote-marks used above are to help the shell split the values correctly. (see below)

System.cmd/2 operates at a level of abstraction lower than that - it expects the caller to provide the command as a string, and the arguments as a list of strings. Because of that, most of the quotes are not only not required, but could cause bugs. For instance:

-H "Content-Type: application/json"
# parsed by the shell as two arguments:
# -H
# Content-Type: application/json

But passing ["-H", "\"Content-Type: application/json\""] to System.cmd will send the double-quotes along to the program, which isn’t the intent.

For the input given, all of these quote-marks are formatting for the shell that isn’t wanted in the actual data sent to curl:

curl -X POST http://localhost:4004/api/converter -H "Content-Type: application/json" -d '{"html": "a", "organization_id": "9213898231sadasd000"}'
                                                    ^                              ^    ^                                                       ^

Post #6

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