Do you have too many git branches on the go at once? Here is the command to list them in order of last modification:
git for-each-ref --sort=-committerdate refs/heads
Python atomic counter
Do you need a thread-safe atomic counter in Python? Use itertools.count():
>>> from itertools import count >>> counter = count() >>> next(counter) 0 >>> next(counter) 1 >>> next(counter) 2
I found this in the decorator package, labelled Atomic get-and-increment provided by the GIL
. So simple! So cool!
git submodule forgetting
Did you forget the -r when cloning a git repo with submodules? The command you’re looking for is git submodule update --init
GitLab YAML Docker Registry client
Have you written a Docker Registry API client in GitLab CI/CD YAML? I have.
# Delete candidate image from CI repository. clean-image: stage: .post except: - main variables: AUTH_API: "$CI_SERVER_URL/jwt/auth" SCOPE: "repository:$CI_PROJECT_PATH" REGISTRY_API: "https://$CI_REGISTRY/v2/$CI_PROJECT_PATH" before_script: - > which jq >/dev/null || (sudo apt-get update && sudo apt-get -y install jq) script: - echo "Deleting $CANDIDATE_IMAGE" - > TOKEN=$(curl -s -u "$CI_REGISTRY_USER:$CI_REGISTRY_PASSWORD" "$AUTH_API?service=container_registry&scope=$SCOPE:delete,pull" | jq -r .token) - > DIGEST=$(curl -s -I -H "Authorization: Bearer $TOKEN" -H "Accept: application/vnd.docker.distribution.manifest.v2+json" "$REGISTRY_API/manifests/$CI_COMMIT_SHORT_SHA" | tr -d "\r" | grep -i "^docker-content-digest: " | sed "s/^[^:]*: *//") - > curl -s -X DELETE -H "Authorization: Bearer $TOKEN" "$REGISTRY_API/manifests/"$(echo $DIGEST | sed "s/:/%3A/g")
sudo tee >/dev/null
Need to redirect to a file from sudo? Use sudo tee >/dev/null:
$ sudo ls -l /root >/root/files.list -bash: /root/files.list: Permission denied $ sudo ls -l /root | sudo tee /root/files.list >/dev/null $ sudo ls -l /root/files.list -rw-r--r-- 1 root root 94 Oct 18 09:31 /root/files.list
Use stdbuf to tee without buffering
Do you want to tee the output of a command to a file, but see it in your terminal too, without buffering? The stdbuf command can do this for you:
$ sudo stdbuf --output=L tcpdump -i any -tttt -n 'udp port 5353' | tee -a tcpdump-mdns
tcpdump: data link type LINUX_SLL2
tcpdump: verbose output suppressed, use -v[v]... for full protocol decode
listening on any, link-type LINUX_SLL2 (Linux cooked v2), snapshot length 262144 bytes
2023-06-15 11:55:16.637670 eth0 M IP 10.0.0.23.5353 > 224.0.0.251.5353: 0 A (QM)? winnebago.local. (28)
2023-06-15 11:55:16.744660 eth0 M IP 10.0.0.42.5353 > 224.0.0.251.5353: 0*- [0q] 1/0/0 (Cache flush) A 10.0.0.42 (38)
...
Which uninstalled package provides a file?
$ apt-file find guestmount guestmount: /usr/bin/guestmount guestmount: /usr/share/bash-completion/completions/guestmount guestmount: /usr/share/doc/guestmount/changelog.Debian.gz guestmount: /usr/share/doc/guestmount/copyright guestmount: /usr/share/man/ja/man1/guestmount.1.gz guestmount: /usr/share/man/man1/guestmount.1.gz guestmount: /usr/share/man/uk/man1/guestmount.1.gz
Scripting DNS lookups
Are you writing a script and some command doesn’t accept hostnames and you don’t want to inline the IP address? dig +short is your friend!
$ dig +short gbenson.net 69.163.152.201
Which APT repository did a package come from?
$ apt policy wget
wget:
Installed: 1.21.2-2ubuntu1
Candidate: 1.21.2-2ubuntu1
Version table:
*** 1.21.2-2ubuntu1 500
500 http://gb.archive.ubuntu.com/ubuntu jammy/main amd64 Packages
100 /var/lib/dpkg/status
Python debugger
By the way, if you’ve never used Python’s debugger, it really is as simple as adding a call to the built-in function breakpoint() at the point you want it to stop.