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snippets

Some pieces of code I find useful for some reason.

Bash

  • tmux new-session -As0
  • tmux setw -g mouse on
  • eval $(ssh-agent), ssh-add -t 1800 (30 minutes), eval $(ssh-agent -k)
  • git log --graph --oneline
  • git fsck
  • git clone --depth=1 ...
  • git tag v1.2.3 && git push --tags
  • git diff --no-index dir1/ dir2/
  • git diff --cached > my.patch, git apply my.patch
  • git clean -dfnX
  • grep -IRi --exclude-dir=.git pattern
  • type python3
  • tar -cvzf archive.tar.gz folder/, tar -xvzf archive.tar.gz
  • curl -fLO https://..., curl -fLo target.zip https://...
  • curl -I https://example.com/, curl -i https://example.com/
  • top and then press xcV. Then W to save the config
  • cd "$(dirname "$0")" useful in a Bash script
  • sudo blkid
  • ffmpeg -i input.mp4 -ss 97 -t 10 output.mp4
  • ffmpeg -i input.jpg -vf 'scale=iw*1/2:ih*1/2' output.jpg
  • ( ow=640; oh=360; ffmpeg -i input.mp4 -vf "scale=$ow:$oh:force_original_aspect_ratio=decrease,pad=$ow:$oh:(ow-iw)/2:(oh-ih)/2" output.mp4 )
  • for i in *.mp3; do echo "$i"; ffmpeg -i "$i" -af volumedetect -vn -sn -dn -f null /dev/null 2>&1 | grep -E '^\[Parsed_volumedetect.+_volume: .+$'; done
  • ffmpeg -i input.mp3 -filter:a 'dynaudnorm=p=0.9:s=5' output.mp3
  • watch -n.2 date
  • scp myfile.txt user@hostname:/home/user/myfile.txt
  • ipfs daemon &, jobs, fg 1, kill %1
  • nohup mycommand &, pgrep mycommand, pkill mycommand
  • find -printf '%p %s %T@\n'
  • rclone lsf -R --format=pst myremote: | LC_ALL=C sort
  • tree -paugh
  • find | grep -i pattern
  • cp -Rv /media/sorcedisk/folder /media/destdisk
  • ss -tulpn
  • df -h
  • du -sh
  • zip -r archive.zip folder/
  • date -u +%Y-%m-%d-%H%M%S
  • less myfile.txt
  • last, lastb, lastlog
  • read -rsp 'Password: ' MYPASSWORD && export MYPASSWORD
  • diff <(ls -l) <(ls -la)
  • ps -aux --sort -pcpu | head -10
  • export SSH_AUTH_SOCK=/run/user/$UID/keyring/ssh
  • python3 -mhttp.server
  • sleep infinity
  • dig @ns1.example.com www.example.com
  • git pull --no-edit && git add . && { git commit "-m$(date +%s)" || :; } && git push
  • find -type d -name .git | while read -r i; do echo "${i:0:-5}"; done
  • git describe --tags --exact-match, git describe --tags --dirty
  • [ -z "$(git status -s)" ]
  • git log --follow --format=%H myfile.txt | while read -r i; do echo -n "$i,$(git show -s --format=%aI "$i"),"; grep -ci 'mypattern' <(git show "$i:./myfile.txt"); done
  • ssh-keygen -t ed25519 -C mydevice -f ~/.ssh/id_ed25519, ssh-keygen -t rsa -b 4096 -C mydevice -f ~/.ssh/id_rsa
  • ansible-playbook -Kk -i hosts.yml playbook.yml -t tags --list-tasks
  • withprefix() { while read -r i; do echo "$1$i"; done }
  • echo Message | mail -s Subject recipient@example.com
  • iostat -o JSON
  • S_COLORS=always watch -d -n.5 --color iostat
  • systemctl -a | grep -Fi myunit (-a = also dead ones), systemctl list-unit-files | grep -Fi myunit (also disabled ones)
  • systemctl list-timers
  • : "${myvar:=myvalue}", export MY_ENV_VAR="${MY_ENV_VAR:-myvalue}"
  • ssh-keygen -R [myserver.example.com]:2222
  • socat - tcp:example.com:80
  • socat UNIX-LISTEN:/tmp/my.sock,mode=777,fork STDOUT, date | socat - UNIX-CONNECT:/tmp/my.sock
  • export XDG_RUNTIME_DIR=/run/user/$UID to use systemctl --user as a linger-enabled user
  • nano -\$v filename, vim -R filename
  • while read -r i; do vboxmanage controlvm myvm keyboardputstring "$i"; vboxmanage controlvm myvm keyboardputscancode 1C 9C; done
  • ssh-keygen -lf <(cat /etc/ssh/ssh_host_*_key.pub)
  • echo 'Hello $USER!' | envsubst
  • sudo tcpdump -wfile.pcap, termshark -rfile.pcap
  • bash <(curl -fsSL https://sh.rustup.rs/) -y && . ~/.cargo/env, rustup update, cargo install rust-script
  • mkfifo mypipe; while :; do date | tee mypipe; done
  • date | curl -sSXPOST "https://api.telegram.org/bot${1#bot}/sendMessage" -dchat_id="$2" --data-urlencode text@- --fail-with-body -w'\n'
  • for i in 192.168.1.1{01..19}; do ping "$i" & done | grep -i 'bytes from .*: icmp_seq='
  • find . -iname \*.mp3 -printf '%P\n' | { echo '#EXTM3U'; while read -r i; do echo "#EXTINF:0,$(basename "${i%.*}")"; echo "file://$HOME/Music/$i"; done; }
  • for i in var_01 VAR_02; do read -rsp "$i: " "${i?}"; if [[ "$i" = [[:upper:]]* ]]; then export "${i?}"; fi; done
  • shuf -en1 Alice Bob Carl
  • tr -cd '0-9A-Za-z' < /dev/random | head -c64; echo
  • myvar=$'string \\ with\nsome\nspecial \'chars\' to "escape"'; echo "${myvar@Q}"
  • find . -iname \*.mp3 -printf '%P\n' | while read -r i; do [[ "$i" =~ ^[0-9A-Za-z\ .\(\)\'/_+-]+$ ]] || echo "$i"; done
  • venv/bin/python3 -mpip install -U --progress-bar=off -r requirements.txt
  • escape_if_any() { echo "${1:+${1@Q}}"; }
  • arr=(one two three); echo "${arr[@]@Q}"; echo "${arr[*]@Q}"
  • vlc -vvv -Idummy --no-audio screen:// --screen-fps=10 --sout='#transcode{vcodec=MJPG,scale=0.5}:standard{access=http,mux=mpjpeg,dst=:8080/}' --sout-http-mime='multipart/x-mixed-replace;boundary=--7b3cc56e5f51db803f790dad720ed50a' --live-caching=100
  • modprobe -r mymod01 mymod02, echo -e 'blacklist mymod01\nblacklist mymod02' > /etc/modprobe.d/blacklist-mymod.conf
  • bind -x '"\e": mycommand'
  • sudo iptables -nvL
  • curl https://api.ipify.org/
Bash
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install -m600 <(echo 'ACTION=="add", SUBSYSTEM=="pci",' \
    'ATTR{vendor}=="0x1234", ATTR{device}=="0x5678", ATTR{remove}="1"') \
    /etc/udev/rules.d/99-disable-pci-example.rules
udevadm trigger -vcadd -spci -avendor=0x1234 -adevice=0x5678
install -m600 <(echo 'ACTION=="add", SUBSYSTEM=="usb",' \
    'ATTR{idVendor}=="1a2b", ATTR{idProduct}=="3c4d", ATTR{remove}="1"') \
    /etc/udev/rules.d/99-disable-usb-example.rules
udevadm trigger -vcadd -susb -aidVendor=1a2b -aidProduct=3c4d
Bash
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user_id=1001; user_name=myuser

loginctl enable-linger "$user_name"
for i in {10..1}; do
    [ -e "/run/user/$user_id/systemd/private" ] && break
    echo "Waiting for systemd user session to initialize (max ${i}s)"
    sleep 1
done
[ -e "/run/user/$user_id/systemd/private" ] ||
    { echo 'Timeout waiting for systemd user session' >&2; exit 1; }

Shell snippets for Docker

  • docker ps -a --format {{.Names}}
  • docker rm -fv mycontainer
  • docker run --rm -v myvolume:/v --log-driver=none docker.io/library/busybox tar -cvzf- -C/v . > mybackup.tar.gz
  • docker run --rm -v myvolume:/v -i docker.io/library/busybox tar -xvzf- -C/v < mybackup.tar.gz
  • docker run -it --rm -p8080:8080 -v "$PWD:/v" php:8 -S '0.0.0.0:8080' -t /v
  • docker run --rm -v "$PWD:/v" -u "$(id -u):$(id -g)" ghcr.io/plantuml/plantuml -tsvg /v
Bash
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docker build -t img-sshsrv01:latest - << 'EOF'
FROM docker.io/library/debian:12
RUN apt-get update && \
    apt-get install -y sudo openssh-server && \
    rm -rf /var/lib/apt/lists/* && \
    mkdir -p /run/sshd
# Warning: leaving the generated host keys in place!
EXPOSE 22
RUN useradd -UGsudo -ms/bin/bash mainuser && \
    echo 'mainuser ALL=(ALL) NOPASSWD: ALL' | \
        install -m440 /dev/stdin /etc/sudoers.d/mainuser-nopassword && \
    echo mainuser:changeme | chpasswd # Warning: very bad password!
ENTRYPOINT ["/usr/sbin/sshd", "-De"]
EOF

docker run -d --name=sshsrv01 -p2222:22 img-sshsrv01:latest

Shell snippets for Podman

  • sudo XDG_RUNTIME_DIR=/run/user/1001 -iu myuser
  • podman ps -ap
  • systemctl --user status podman-kube@$(systemd-escape ~/kube.yaml)
  • journalctl --user -u podman-kube@$(systemd-escape ~/kube.yaml)
  • ls -la ~/.local/share/containers/storage/volumes
  • (read -rsp 'Password: ' && echo -e "{\"main\":\"$(echo -n "$REPLY" | base64 -w0)\"}") | podman secret create mypassword -
  • echo -e "{\"main\":\"$(base64 -w0 < mykey.pem)\"}" | podman secret create mykey -
  • podman image ls -a, podman image prune -af

Shell snippets for Kubernetes

  • kubectl get all -A, kubectl get pod -owide, kubectl get pod -w
  • kubectl run mypod --image=docker.io/library/debian:12 sleep infinity
  • kubectl exec -it mypod -- bash
  • kubectl delete pod/mypod
  • kubectl config current-context, kubectl config use-context mycontext
  • kubectl --context=mycontext -nmynamespace get pod
  • kubectl port-forward pod/mypod '8080:80'
  • kubectl get secret/mysecret -ojsonpath={.data.password} | base64 -d; echo
  • time kubectl api-resources --verbs=list -oname | xargs -n1 kubectl get -A -owide --show-kind --ignore-not-found
  • helm repo add bitnami https://charts.bitnami.com/bitnami && helm repo update
  • helm --kube-context=mycontext -nmynamespace list
Bash
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kubectl apply -f- << 'EOF'
---
apiVersion: v1
kind: Pod
metadata:
  name: mypod
spec:
  containers:
    - name: main
      image: docker.io/library/debian:12
      args: [sleep, infinity]
      volumeMounts: [{ mountPath: /v, name: v, readOnly: true }]
  volumes:
    - name: v
      persistentVolumeClaim: { claimName: mypvc, readOnly: true }
EOF

Git Bash (Windows)

  • export MSYS_NO_PATHCONV=1
  • winpty rclone ncdu .
  • choco list --local-only
  • sudo choco upgrade -y all
  • sudo choco install -y rclone winfsp && rclone mount myremote: X:
  • [[ "$(uname)" = MINGW* ]]; echo $?

Prometheus queries

  • abs(mymetric - mymetric offset 1m)