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willist/tricks.rst

Last active December 14, 2015 15:49
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Unix tricks
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tricks.rst

Bash

  • ctrl-r searches your command history as you type
  • Add set -o vi in your ~/.bashrc to make use the vi keybindings instead of the Emacs ones. Takes some time to get used to, but it's fantastic!
  • Input from the commandline as if it were a file by replacing command < file.in with command <<< "some input text"
  • '^' is a sed-like operator to replace chars from last command ls docs; ^docs^web^ is equal to ls web The second argument can be empty.
  • '!!:n' selects the nth argument of the last command, and '!$' the last arg 'ls file1 file2 file3; cat !!:1-2' shows all files and cats only 1 and 2
  • More in-line substitutions: http://tiny.cc/ecv0cw
  • 'nohup ./long_script &' to leave stuff in background even if you logout
  • 'cd -' change to the previous directory you were working on
  • 'ctrl-x ctrl-e' opens an editor to work with long or complex command lines
  • Use traps for cleaning up bash scripts on exit http://tiny.cc/traps
  • 'shopt -s cdspell' automatically fixes your 'cd folder' spelling mistakes

Pseudo Aliases for Commonly Used Long Commands

  • function lt() { ls -ltrsa "$@" | tail; }
  • function psgrep() { ps axuf | grep -v grep | grep "$@" -i --color=auto; }
  • function fname() { find . -iname "$@"; }

Vim

  • ':set spell' activates vim spellchecker. Use ']s' and '[s' to move between mistakes, 'zg' adds to the dictionary, 'z=' suggests correctly spelled words
  • check my .vimrc http://tiny.cc/qxzktw and here http://tiny.cc/kzzktw for more

Tools

  • 'htop' instead of 'top'
  • 'ranger' is a nice console file manager for vi fans
  • Use 'apt-file' to see which package provides that file you're missing
  • 'dict' is a commandline dictionary
  • Learn to use 'find' and 'locate' to look for files
  • Compile your own version of 'screen' from the git sources. Most versions have a slow scrolling on a vertical split or even no vertical split at all
  • 'trash-cli' sends files to the trash instead of deleting them forever. Be very careful with 'rm' or maybe make a wrapper to avoid deleting '*' by accident (e.g. you want to type 'rm tmp*' but type 'rm tmp *')
  • 'file' gives information about a file, as image dimensions or text encoding
  • 'awk '!x[$0]++'' to check for duplicate lines
  • 'echo start_backup.sh | at midnight' starts a command at the specified time
  • Pipe any command over 'column -t' to nicely align the columns
  • Google 'magic sysrq' and learn how to bring you machine back from the dead
  • 'diff --side-by-side fileA.txt fileB.txt | pager' to see a nice diff
  • 'j.py' http://tiny.cc/62qjow remembers your most used folders and is an incredible substitute to browse directories by name instead of 'cd'
  • 'dropbox_uploader.sh' http://tiny.cc/o2qjow is a fantastic solution to upload by commandline via Dropbox's API if you can't use the official client
  • learn to use 'pushd' to save time navigating folders (j.py is better though)
  • if you liked the 'psgrep' alias, check 'pgrep' as it is far more powerful
  • never run 'chmod o+x * -R', capitalize the X to avoid executable files. If you want _only_ executable folders: 'find . -type d -exec chmod g+x {} ;'
  • 'xargs' gets its input from a pipe and runs some command for each argument

NETWORKING

  • Don't know where to start? SMB is usually better than NFS for most cases. 'sshfs_mount' is not really stable, any network failure will be troublesome

  • 'python -m SimpleHTTPServer 8080' shares all the files in the current folder over HTTP, port 8080

  • 'ssh -R 12345:localhost:22 server.com "sleep 1000; exit"' forwards server.com's port 12345 to your local ssh port, even if you machine is not externally visible on the net. Now you can 'ssh localhost -p 12345' from server.com and you will log into your machine. 'sleep' avoids getting kicked out from server.com for inactivity

  • Read on 'ssh-keygen' to avoid typing passwords every time you ssh

  • 'socat TCP4-LISTEN:1234,fork TCP4:192.168.1.1:22' forwards your port 1234 to another machine's port 22. Very useful for quick NAT redirection.

  • Configure postfix to use your personal Gmail account as SMTP: http://tiny.cc/n5k0cw. Now you can send emails from the command line. 'echo "Hello, User!" | mail [email protected]'

  • Some tools to monitor network connections and bandwith: 'lsof -i' monitors network connections in real time 'iftop' shows bandwith usage per connection 'nethogs' shows the bandwith usage per process

  • Use this trick on .ssh/config to directly access 'host2' which is on a private network, and must be accessed by ssh-ing into 'host1' first Host host2

    ProxyCommand ssh -T host1 'nc %h %p' HostName host2

  • Pipe a compressed file over ssh to avoid creating large temporary .tgz files 'tar cz folder/ | ssh server "tar xz"' or even better, use 'rsync'

    -~-

Credit

Taken from http://mmb.pcb.ub.es/~carlesfe/unix/tricks.txt and augmented with information from http://www.reddit.com/r/programming/comments/19uiim/unix_tricks_you_should_be_using/

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