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Created November 13, 2018 00:49
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bash.md

I have marked with a * those which I think are absolutely essential Items for each section are sorted by oldest to newest. Come back soon for more!

BASH

  • In bash, 'ctrl-r' searches your command history as you type
  • 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.
  • '!!' expands to the last typed command. Useful for root commands: 'cat /etc/...' [permission denied] 'sudo !!'
  • '!!:n' selects the nth argument of the last command, and '!$' the last arg 'ls file1 file2 file3; cat !!:1-2' shows all files and cats only 1 and 2
  • 'ESC-.' fetches the last parameter of the previous command
  • Related, include 'shopt -s histverify histreedit' on your .bashrc to double-check all expansions before submitting a command
  • 'nohup ./long_script &' to leave stuff in background even if you logout
  • 'cd -' change to the previous directory you were working on
  • 'ctrl-x ctrl-e' opens an editor to work with long or complex command lines
  • Use traps for cleaning up bash scripts on exit http://tldp.org/LDP/Bash-Beginners-Guide/html/sect_12_02.html
  • 'shopt -s cdspell' automatically fixes your 'cd folder' spelling mistakes
  • Add 'set editing-mode vi' in your ~/.inputrc to use the vi keybindings for bash and all readline-enabled applications (python, mysql, etc)
  • Aggregate history of all terminals in the same .history. On your .bashrc: shopt -s histappend export HISTSIZE=100000 export HISTFILESIZE=100000 export HISTCONTROL=ignoredups:erasedups export PROMPT_COMMAND="history -a;history -c;history -r;$PROMPT_COMMAND"
  • Pressed 'Ctrl-s' by accident and the terminal is frozen? Unfreeze: 'Ctrl-Q'

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 "$@"; }
  • function remove_lines_from() { grep -F -x -v -f $2 $1; } removes lines from $1 if they appear in $2
  • alias pp="ps axuf | pager"
  • alias sum="xargs | tr ' ' '+' | bc" ## Usage: echo 1 2 3 | sum
  • function mcd() { mkdir $1 && cd $1; }

VIM

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. Alternatively, use 'tmux', though it is not as ubiquitous as 'screen'.
  • '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
  • 'sort -u' 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' to bring a Linux machine back from the dead
  • 'diff --side-by-side fileA.txt fileB.txt | pager' to see a nice diff
  • 'j.py' https://github.com/rupa/j2 remembers your most used folders and is an incredible substitute to browse directories by name instead of 'cd'
  • 'dropbox_uploader.sh' lets you upload by commandline via Dropbox's API without the official client https://github.com/andreafabrizi/Dropbox-Uploader
  • 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
  • run jobs in parallel easily: 'ls *.png | parallel -j4 convert {} {.}.jpg'
  • grep has a '-c' switch that counts occurences. Don't pipe grep to 'wc -l'.
  • 'man hier' explains the filesystem folders for new users
  • 'tree' instead of 'ls -R'
  • Recover corrupt zip files: First, make copies and ALWAYS WORK ON A COPY First: 'zip -F corrupt_copy1.zip --out recover1.zip' Then: 'zip -FF corrupt_copy2.zip --out recover2.zip' Last: 'ditto -x -k corrupt_copy3.zip --out out_folder/' Merge the contents of the two recovered zipfiles and the out_folder. You will be able to recover most of the data.
  • Use GNU datamash for basic numerical, textual and statistical operations on text files: 'seq 10 | datamash sum 1 mean 1'

NETWORKING

  • Don't know where to start? SMB is usually better than NFS for newbies. If really you know what you are doing, then NFS is the way to go.
  • If you use 'sshfs_mount' and suffer from disconnects, use '-o reconnect,workaround=truncate:rename'
  • 'python -m SimpleHTTPServer 8080' or 'python3 -mhttp.server localhost 8080' shares all the files in the current folder over HTTP.
  • 'ssh -R 12345:localhost:22 -N server.com' forwards server.com's port 12345 to your local ssh port, even if you machine is behind a firewall/NAT. 'ssh localhost -p 12345' from server.com will get you in your machine.
  • Read on 'ssh-agent' to strenghten your ssh connections using private keys, while avoiding 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.
  • 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 t∏o avoid creating large temporary .tgz files 'tar cz folder/ | ssh server "tar xz"' or even better, use 'rsync'
  • ssmtp can use a Gmail account as SMTP and send emails from the command line. 'echo "Hello, User!" | mail user@domain.com' ## Thanks to Adam Ziaja. Configure your /etc/ssmtp/ssmtp.conf: root=E-MAIL mailhub=smtp.gmail.com:587 rewriteDomain= hostname=smtp.gmail.com:587 UseSTARTTLS=YES UseTLS=YES AuthUser=E-MAIL AuthPass=PASSWORD AuthMethod=LOGIN FromLineOverride=YES
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