Alpine 3.11 diff: unrecognized option: c BusyBox v1.31.1 () multi-call binary - linux

Question

I am using an alpine 3.11 to build my image, everything goes well during the build the dockefile is here below :
FROM alpine:3.11
LABEL version="1.0"
ARG UID="110"
ARG PYTHON_VERSION="3.8.10-r0"
ARG ANSIBLE_VERSION="5.0.1"
ARG AWSCLI_VERSION="1.22.56"
# Create jenkins user with sudo privileges
RUN adduser -u ${UID} -D -h /home/jenkins/ jenkins
RUN echo 'jenkins ALL=(ALL) NOPASSWD:ALL' >> /etc/sudoers
RUN mkdir -p /tmp/.ansible
RUN chown -R jenkins:jenkins /tmp/.ansible
# Install minimal packages
RUN apk --update --no-cache add bash bind-tools curl gcc git libffi-dev libpq make mysql-client openssl postgresql-client sudo unzip wget coreutils
#RUN apk --update --no-cache add py-mysqldb
RUN apk --update --no-cache add python3=${PYTHON_VERSION} python3-dev py3-pip py3-cryptography
# Install JQ from sources
RUN wget https://github.com/stedolan/jq/releases/download/jq-1.5/jq-linux64
RUN mv jq-linux64 /usr/bin/jq
RUN chmod +x /usr/bin/jq
# Install ansible and awscli with python package manager
RUN pip3 install --upgrade pip
RUN pip3 install yq --ignore-installed PyYAML
RUN pip3 install ansible==${ANSIBLE_VERSION}
RUN pip3 install awscli==${AWSCLI_VERSION} boto boto3 botocore s3cmd pywinrm pymysql 'python-dateutil<2.8.1'
# Clean cache
RUN rm -rf /var/cache/apk/*
# Display packages versions
RUN python3 --version && \
pip3 --version && \
ansible --version && \
aws --version
this image is later used to lunch some jenkins jobs nothing unusual.
But when i try to use the diff command in of these jobs I have the following error :
diff: unrecognized option: c BusyBox v1.31.1 () multi-call binary
that's why i tried to install the coreutils package but still the "-c" option is still unrecognized which is weird.
So my question is there a way to add the -c option for the diff command because in the manual of GNU this should be available automatically but apparently not on Alpine ? if there is a way could anyone please share it.
P.S : In case you are wondering why am I using the diff command it is just to compare two json files and the -c is necessary for me in this context.

Answer 1

Well I just had to add the diffutils package to the list after installing it everything works well

Answer 2

In spite of it being required in the POSIX diff specification it looks like the BusyBox implementation of diff doesn't support the -c option.
One thing you could do is change your diff invocation to use unified context diff format. Again, BusyBox diff appears to not support -u, so you need to use an explicit -U option with the number of lines of context
diff -U3 file.orig file.new
In general, the Alpine environment has many small differences like this. If you're installing the GNU versions of these tools anyways – your Dockerfile already installs GNU bash and coreutils – you'll probably find minimal to no space savings from using an Alpine base image, and using a Debian or Ubuntu base that already includes the GNU versions of these tools will be easier.
FROM ubuntu:20.04 # not Alpine
...
RUN apt-get update \
&& DEBIAN_FRONTEND=noninteractive \
apt-get install --no-install-recommends --assume-yes \
bind9-utils \
build-essential \
curl \
git-core \
...
You may need to search on https://packages.debian.org/ to find equivalent Debian packages. build-essential is a metapackage that includes the entire C toolchain (gcc, make, et al.); bash, coreutils, and diffutils would typically be installed as part of the base distribution image.