cnd

status: working and in production (for myself only as far as I'm aware)

A simple commandline tool to help you automate things; cnd is short for check-n-do and provides some sugar as long as your problem fits the following pattern:

• Check the state of something against the last time it was checked
• If changed, execute an action

Concept

The user can invoke cnd as many times as they like, the given check will execute but the given do will only execute if the result of the check differed from the last time cnd was ran.

Installation

go install github.com/initialed85/cnd@latest

Usage

cnd \
  -job '(an optional job name; defaults to the current working directory name)' \
  -check '(a command that gathers our comparison state)' \
  -do '(a command that executes an action)'

Example

Redeploying a service when a Git repo changes

cnd -check 'git pull >/dev/null 2>&1 && git log -b master HEAD~1..HEAD' -do 'make down ; make up'

When executed and there are no changes, the output will look something like this:

2022/09/21 09:03:36 check-n-do; jobName="dinosaur"
2022/09/21 09:03:36 check; command="git pull >/dev/null 2>&1 && git log -b master HEAD~1..HEAD"
2022/09/21 09:03:38 check; output="commit e03e2d359daf575e242b15c1c8d70a013b85b199\nAuthor: Edward Beech <initialed85@gmail.com>\nDate:   Wed Sep 21 16:57:04 2022 +0800\n\n    Empty commit to see if my ghetto CD stuff is working"
2022/09/21 09:03:38 check; lastOutput="commit e03e2d359daf575e242b15c1c8d70a013b85b199\nAuthor: Edward Beech <initialed85@gmail.com>\nDate:   Wed Sep 21 16:57:04 2022 +0800\n\n    Empty commit to see if my ghetto CD stuff is working"
2022/09/21 09:03:38 check; changed=false

And if there are changes, the output will look something like this:

2022/09/21 09:04:36 check-n-do; jobName="dinosaur"
2022/09/21 09:04:36 check; command="git pull >/dev/null 2>&1 && git log -b master HEAD~1..HEAD"
2022/09/21 09:04:39 check; output="commit c8d7ccd6d0c820f14856e33f48fce6c3a1a634db\nAuthor: Edward Beech <initialed85@gmail.com>\nDate:   Wed Sep 21 17:04:29 2022 +0800\n\n    Another empty commit to see if my ghetto CD stuff is working"
2022/09/21 09:04:39 check; lastOutput="commit e03e2d359daf575e242b15c1c8d70a013b85b199\nAuthor: Edward Beech <initialed85@gmail.com>\nDate:   Wed Sep 21 16:57:04 2022 +0800\n\n    Empty commit to see if my ghetto CD stuff is working"
2022/09/21 09:04:39 check; changed=true
2022/09/21 09:04:39 do; command="make down ; make up"
2022/09/21 09:04:44 do; output="docker compose -f docker/docker-compose.yml down --remove-orphans --volumes || true\nContainer docker-frontend-1  Stopping\nContainer docker-frontend-1  Stopping\nContainer docker-backend-1  Stopping\nContainer docker-backend-1  Stopping\nContainer docker-backend-1  Stopped\nContainer docker-backend-1  Removing\nContainer docker-backend-1  Removed\nContainer docker-frontend-1  Stopped\nContainer docker-frontend-1  Removing\nContainer docker-frontend-1  Removed\nNetwork dinosaur-internal  Removing\nNetwork dinosaur-external  Removing\nNetwork dinosaur-internal  Removed\nNetwork dinosaur-external  Removed\ndocker build -t dinosaur-session -f docker/session/Dockerfile ./docker/session\nSending build context to Docker daemon  8.704kB\r\r\nStep 1/22 : FROM ubuntu:22.04\n ---> 2dc39ba059dc\nStep 2/22 : RUN apt-get update &&     apt-get install -y     curl git npm entr     golang-1.18 python3 default-jdk lua5.4 luarocks     procps file strace screen     net-tools inetutils-ping traceroute netcat tcpdump iproute2\n ---> Using cache\n ---> e945329d79f9\nStep 3/22 : RUN npm install -g typescript ts-node\n ---> Using cache\n ---> 46717d934463\nStep 4/22 : RUN curl https://sh.rustup.rs -sSf | sh -s -- -y\n ---> Using cache\n ---> 518759e3badb\nStep 5/22 : ENV PATH=${PATH}:/usr/lib/go-1.18/bin:/root/go/bin/:/root/.cargo/bin\n ---> Using cache\n ---> 0ab91dbee20b\nStep 6/22 : RUN go install github.com/sorenisanerd/gotty@latest\n ---> Using cache\n ---> ca817ab25f1b\nStep 7/22 : RUN mkdir -p /srv/cmd/\n ---> Using cache\n ---> 0c226f0dc3f9\nStep 8/22 : WORKDIR /srv/\n ---> Using cache\n ---> 9383bb62d031\nStep 9/22 : RUN luarocks install luasocket\n ---> Using cache\n ---> f5529435e81c\nStep 10/22 : RUN npm i --save-dev @types/node\n ---> Using cache\n ---> 7aa1a6c9f2ef\nStep 11/22 : RUN echo 'termcapinfo xterm* ti@:te@' >> /root/.screenrc\n ---> Using cache\n ---> 8b8e167d5e6d\nStep 12/22 : COPY docker-entrypoint.sh /docker-entrypoint.sh\n ---> Using cache\n ---> 91b0e7c1d04e\nStep 13/22 : COPY loop.sh /loop.sh\n ---> Using cache\n ---> 1baa4281d86d\nStep 14/22 : COPY build.sh /build.sh\n ---> Using cache\n ---> b779bc5c4f28\nStep 15/22 : COPY run.sh /run.sh\n ---> Using cache\n ---> d866e4bfe5f9\nStep 16/22 : COPY watch.sh /watch.sh\n ---> Using cache\n ---> eb766bb51055\nStep 17/22 : ENV GOTTY_PORT=${GOTTY_PORT:-8080}\n ---> Using cache\n ---> 63577e48f262\nStep 18/22 : ENV GOTTY_PATH=${GOTTY_PATH}\n ---> Using cache\n ---> 799685a63c38\nStep 19/22 : ENV BASE_FOLDER_PATH=${BASE_FOLDER_PATH:-/srv/}\n ---> Using cache\n ---> 64be509c0a1d\nStep 20/22 : ENV BUILD_CMD=${BUILD_CMD}\n ---> Using cache\n ---> 0b290e0759b2\nStep 21/22 : ENV RUN_CMD=${RUN_CMD}\n ---> Using cache\n ---> f5758eec0880\nStep 22/22 : ENTRYPOINT [\"/docker-entrypoint.sh\"]\n ---> Using cache\n ---> 08ee7a337db7\nSuccessfully built 08ee7a337db7\nSuccessfully tagged dinosaur-session:latest\ndocker compose -f docker/docker-compose.yml build --parallel\n#1 [docker-backend internal] load build definition from Dockerfile\n#1 transferring dockerfile: 32B 0.0s done\n#1 DONE 0.1s\n\n#2 [docker-frontend internal] load build definition from Dockerfile\n#2 transferring dockerfile: 32B 0.1s done\n#2 DONE 0.1s\n\n#3 [docker-frontend internal] load .dockerignore\n#3 transferring context: 2B done\n#3 DONE 0.0s\n\n#4 [docker-backend internal] load .dockerignore\n#4 transferring context: 2B 0.0s done\n#4 DONE 0.0s\n\n#5 [docker-backend internal] load metadata for docker.io/library/ubuntu:22.04\n#5 DONE 0.0s\n\n#6 [docker-backend internal] load metadata for docker.io/library/golang:1.18\n#6 DONE 1.9s\n\n#7 [docker-frontend internal] load metadata for docker.io/library/node:14.20.0\n#7 DONE 1.9s\n\n#8 [docker-backend stage-1  1/11] FROM docker.io/library/ubuntu:22.04\n#8 DONE 0.0s\n\n#9 [docker-backend build 1/9] FROM docker.io/library/golang:1.18@sha256:040bc0980888e2df09499c73156f3f869d843b7033d11b465fee7f1a358a494a\n#9 DONE 0.0s\n\n#10 [docker-backend internal] load build context\n#10 transferring context: 2.57kB 0.0s done\n#10 DONE 0.0s\n\n#11 [docker-backend stage-1  7/11] RUN mkdir -p /srv/pkg/sessions/languages\n#11 CACHED\n\n#12 [docker-backend stage-1  3/11] RUN curl -fsSL https://download.docker.com/linux/ubuntu/gpg | gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg\n#12 CACHED\n\n#13 [docker-backend stage-1  6/11] WORKDIR /srv/\n#13 CACHED\n\n#14 [docker-backend build 6/9] COPY cmd /srv/cmd\n#14 CACHED\n\n#15 [docker-backend stage-1  8/11] COPY pkg/sessions/languages /srv/pkg/sessions/languages\n#15 CACHED\n\n#16 [docker-backend stage-1 10/11] COPY docker/session /srv/docker/session\n#16 CACHED\n\n#17 [docker-backend stage-1  9/11] RUN mkdir -p /srv/docker/\n#17 CACHED\n\n#18 [docker-backend build 3/9] COPY go.mod /srv/go.mod\n#18 CACHED\n\n#19 [docker-backend build 8/9] COPY pkg /srv/pkg\n#19 CACHED\n\n#20 [docker-backend build 7/9] COPY internal /srv/internal\n#20 CACHED\n\n#21 [docker-backend stage-1  2/11] RUN apt-get update && apt-get install -y ca-certificates curl gnupg lsb-release golang-1.18\n#21 CACHED\n\n#22 [docker-backend build 5/9] RUN --mount=type=cache,target=/root/.cache/go-build go mod download\n#22 CACHED\n\n#23 [docker-backend stage-1  4/11] RUN echo   \"deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/docker-archive-keyring.gpg] https://download.docker.com/linux/ubuntu   $(lsb_release -cs) stable\" | tee /etc/apt/sources.list.d/docker.list > /dev/null\n#23 CACHED\n\n#24 [docker-backend build 9/9] RUN --mount=type=cache,target=/root/.cache/go-build go build -v -o main /srv/cmd/main.go\n#24 CACHED\n\n#25 [docker-backend build 2/9] WORKDIR /srv/\n#25 CACHED\n\n#26 [docker-backend stage-1  5/11] RUN apt-get update && apt-get install -y docker-ce docker-ce-cli containerd.io docker-compose-plugin\n#26 CACHED\n\n#27 [docker-backend build 4/9] COPY go.sum /srv/go.sum\n#27 CACHED\n\n#28 [docker-backend stage-1 11/11] COPY --from=build /srv/main /srv/main\n#28 CACHED\n\n#29 [docker-frontend internal] load metadata for docker.io/library/nginx:1.23.1\n#29 DONE 1.9s\n\n#30 [docker-backend] exporting to image\n#30 exporting layers done\n#30 writing image sha256:a638b17a3f22988e74afc7a11f62b042103b882729fa578ed78ed01fca23813a done\n#30 naming to docker.io/library/docker-backend done\n#30 DONE 0.0s\n\n#31 [docker-frontend build 1/9] FROM docker.io/library/node:14.20.0@sha256:6adfb0c2a9db12a06893974bb140493a7482e2b3df59c058590594ceecd0c99b\n#31 DONE 0.0s\n\n#32 [docker-frontend stage-1 1/4] FROM docker.io/library/nginx:1.23.1@sha256:0b970013351304af46f322da1263516b188318682b2ab1091862497591189ff1\n#32 DONE 0.0s\n\n#33 [docker-frontend internal] load build context\n#33 transferring context: 1.20MB 0.0s done\n#33 DONE 0.0s\n\n#34 [docker-frontend build 6/9] COPY frontend/tsconfig.json /srv/tsconfig.json\n#34 CACHED\n\n#35 [docker-frontend build 8/9] COPY frontend/public /srv/public\n#35 CACHED\n\n#36 [docker-frontend build 4/9] COPY frontend/package-lock.json /srv/package-lock.json\n#36 CACHED\n\n#37 [docker-frontend stage-1 2/4] COPY docker/frontend/default.conf /etc/nginx/conf.d/default.conf\n#37 CACHED\n\n#38 [docker-frontend build 3/9] COPY frontend/package.json /srv/package.json\n#38 CACHED\n\n#39 [docker-frontend build 7/9] COPY frontend/src /srv/src\n#39 CACHED\n\n#40 [docker-frontend build 9/9] RUN npm run build\n#40 CACHED\n\n#41 [docker-frontend stage-1 3/4] COPY --from=build /srv/build/static /usr/share/nginx/html/static\n#41 CACHED\n\n#42 [docker-frontend build 2/9] WORKDIR /srv/\n#42 CACHED\n\n#43 [docker-frontend build 5/9] RUN npm ci\n#43 CACHED\n\n#44 [docker-frontend stage-1 4/4] COPY --from=build /srv/build/* /usr/share/nginx/html/\n#44 CACHED\n\n#30 [docker-frontend] exporting to image\n#30 exporting layers done\n#30 writing image sha256:6458f8593ff555f1a6ef183ea5d2f0e1402538bcb1226ea9934cbb5ddc1790f8 done\n#30 naming to docker.io/library/docker-frontend done\n#30 DONE 0.0s\n\nUse 'docker scan' to run Snyk tests against images to find vulnerabilities and learn how to fix them\ndocker compose -f docker/docker-compose.yml up -d\nNetwork dinosaur-internal  Creating\nNetwork dinosaur-internal  Created\nNetwork dinosaur-external  Creating\nNetwork dinosaur-external  Created\nContainer docker-frontend-1  Creating\nContainer docker-backend-1  Creating\nContainer docker-frontend-1  Created\nContainer docker-backend-1  Created\nContainer docker-backend-1  Starting\nContainer docker-frontend-1  Starting\nContainer docker-frontend-1  Started\nContainer docker-backend-1  Started"
2022/09/21 09:04:44 check-n-do; done=true

If you wanted to run the above every minute as a cron job; edit your crontab with crontab -e and add something like the following:

  * *  *   *   *     PATH=${PATH}:${HOME}/go/bin /usr/bin/bash -c "cd ${HOME}/Projects/Home/dinosaur && cnd -check 'git pull >/dev/null 2>&1 && git log -b master HEAD~1..HEAD' -do 'make down ; make up'"

I find cron to be a real pain in the neck (at least for Ubuntu) with its default shell, path etc so all that boilerplate helps make that transparent.