How to pipe in data to dockerified app on docker run? - docker

Question

I have dockerified httpie via this Dockerfile:
FROM alpine:3.6
MAINTAINER Philipp Kretzschmar <philipp.kretzschmar#gmail.com>
ENV LAST_UPDATED=2017-06-01
ARG XDG_CACHE_HOME=/tmp/cache/
RUN apk update && \
apk add py-pip && pip install httpie && \
rm -rf /var/cache/apk/*
CMD ["--help"]
ENTRYPOINT ["/usr/bin/http"]
You can also pull the image directly:
docker pull k0pernikus/httpie-docker-alpine:1.0.0
Using httpie as a standalone program, I know it is recommended to pipe in a nested json payload via echo (simplified example):
$ echo '{"property":"value"}' | http PUT https://jsonplaceholder.typicode.com -vvv
And through the verbose output flag -vvv httpie shows that the payload was indeed sent in the request:
PUT /posts HTTP/1.1
Accept: application/json, */*
Accept-Encoding: gzip, deflate
Connection: keep-alive
Content-Length: 21
Content-Type: application/json
Host: jsonplaceholder.typicode.com
User-Agent: HTTPie/0.9.9
{
"property": "value"
}
(The jsonplaceholder URL will return 404, which is fine. This question's scope is only about sending the proper request.)
Now I thought that it would be equivalent to execute the command through docker via:
$ echo '{"property":"value"}' | docker run k0pernikus/httpie-docker-alpine:1.0.0 PUT https://jsonplaceholder.typicode.com -vvv
But the verbose flag reports that the request was send without the payload:
PUT / HTTP/1.1
Content-Length: 0
Accept-Encoding: gzip, deflate
Host: jsonplaceholder.typicode.com
Accept: */*
User-Agent: HTTPie/0.9.9
Connection: keep-alive
How can I pipe in the data to the docker run command?

Answer 1

You need to use the -i flag to docker run in order to keep stdin open. Compare:
$ echo hello | docker run --rm alpine cat
$
To:
$ echo hello | docker run -i --rm alpine cat
hello
$