Shell for Developers (1)

Contents

• Due to limited time this first part covers only three topics

• Bash

• VIm

• screen

• The remaining 99% will be subject of another talk.

Why should you care?

• You knowledge will work on many systems

  Many unixoid systems share a similar user-land including most Linux distributions.

• Extremely powerful

  …once you know the commands and internalized them. Muscle memory FTW!

• Efficient data manipulation

  Replace your code monkeys with a short script

• Brag in front of your colleagues

  I know you want it, too!

Bash

• Standard shell on many Linux distributions

  /bin/sh often a symlink to /bin/bash. But not on Ubuntu Linux!

• Available on many operating systems

  Practically all Linux distributions and Unices like FreeBSD and MacOS X.

• Powerful feature set

  You probably don't know most of the features yet

• Side note

  Z shell is a very powerful alternative to Bash.

Bash - history

• history shows your current $HISTFILE (usually ~/.bash_history
• Ctrl-P for going to the previous history entry, Ctrl-N to go to the next history entry.
• Ctrl-O executes the currently selected history entry and selects the following history entry.
• Ctrl-R for searchable reverse history. Also Ctrl-R to page through history.
  
• Ctrl-S is forward search, but usually this combo is already taken.
• Alt-. to get the argument of the previous history entry.
• Ctrl-X Ctrl-E to open the current command line in $EDITOR.
• !! repeats the last command, e. g. sudo !!.
• ^search^replace repeats the last command but replaces the given string.
• !command to run the last history entry starting with command, e. g. !ls.

Bash - keyboard shortcuts

• Output control

  Ctrl-S suspends output (XOFF), Ctrl-Q resumes output (XON).

• Navigation

  • Ctrl-A to navigate to the beginning of the command line, like Home.
  • Ctrl-E to navigate to the end of the command line, like End.
  • Alt-F or Ctrl-Right to move a word forward, Alt-B or Ctrl-Left to move a word backward.
  • Ctrl-L to clear the screen, like clear.

Bash - completion

• Tab to get suggestions for text before cursor.
• Alt-? to show list of suggestions for text before cursor.
• Alt-* to insert all suggestions for text before cursor.
• Alt-{ to perform filename completion and insert the list of possible completions enclosed within braces.

• "Typed" completions

  • Alt-/ to suggest filenames
  • Alt-~ to suggest usernames
  • Alt-$ to suggest variables
  • Alt-@ to suggest hostnames
  • Alt-! to suggest commands

Bash - word manipulations

• Ctrl-V to prepare a quoted insert, e. g. get a literal escape code.
• Ctrl-T to transpose characters before and under cursor.
• Alt-T to transpose words before and under cursor.
• Alt-U to uppercase characters of word under and after cursor.
• Alt-L to lowercase characters of word under and after cursor.
• Alt-L to capitalize characters of word under and after cursor.

Bash - killing and yanking

• Basically just cut and paste. Content is placed in "kill ring" (stack).
• Ctrl-K to cut text from cursor to end of line.
• Ctrl-U to cut text from cursor to beginning of line.
• Ctrl-W to cut word before cursor.
• Alt-D to cut word behind cursor.
• Ctrl-Y to paste the top of the kill ring.
• Alt-Y to cycle through the kill ring and set new top.

Bash - directory navigation

• pwd to print working directory.
• cd - to enter the previous directory.
• dirs to show current directory stack.
• pushd to push working directory on stack.
• popd to change to the top directory on stack.

Bash - control structures

• This talk isn't about writing shell scripts, so only a short overview.

• for $VAR in $LIST; do your_stuff; more_stuff; done

• while $CONDITION; do your_stuff; more_stuff; done

• if [[ $COND1 ]]; then do_foo; elif [[ $COND2 ]]; then do_bar; else do_baz; fi

• case $WORD in $PATTERN1) do_foo ;; $PATTERN2) do_bar ;; *) do_baz ;; esac

Bash - job control

• Ctrl-Z suspends a job.
• fg moves it into foreground.
• bg move it into background.
• Start a job in background by adding a trailing ampersand, e. g. sleep 120 &.
• jobs lists all jobs of your current shell process.
• kill can kill jobs (not only processes), e. g. kill %1
• disown uncouples a job from your shell so it keeps running when you exit the shell.

VIm

• Best editor™

  Once you grok the basics, it's very powerful

• Two modes: command and insert mode

  Use : to get in command mode.

• Get a good .vimrc file to get more out of VIm

• Get a good cheat sheet ;)

  vi/vim graphical cheat sheet

• Of course Bash also supports vi input mode ;)

  set -o vi

VIm - some useful commands

• :syntax on to activate syntax highlighting (if not already in your .vimrc).
• :next or :n to open next file, :previous or :N to open previous file.
• :wq or :x or ZZ to save current file and quit.
• :r filename to insert contents of file at current cursor position.
• . to repeat the last action.
• % to jump to matching bracket.
• u or :undo to undo last change.
• Ctrl-R or :redo to redo last undone change.
• :sh run $SHELL.
• :!command run command and display output.
• :.!command insert output of command on cursor position.

VIm - text manipulation

• In command mode (only some examples)

  In general: <count><command><scope>, e. g. 5dw to cut the five words following the cursor.

  • v to start visual selection, end with command.
  • dw to cut word under cursor.
  • yy to copy current line.
  • 5yy to copy five lines under the cursor.
  • p to paste after cursor, P to paste before cursor.
  • C to cut line from cursor to end of line and enter insert mode.
  • Ctrl-A to increment, Ctrl-X to decrement number under cursor.

• In insert mode

  • Ctrl-N or Ctrl-P to do forward or backward keyword completion.

VIm - window management

• :split (file) or Ctrl-W s to horizontally split window (and open file).
• :vsplit (file) or Ctrl-W v to vertically split window (and open file).
• Ctrl-W w to switch to next window.
• Ctrl-W q to close the current window.

VIm - search and destroy replace

• * to search for word under the cursor.
• /foo to forward search for term foo (also works with regular expressions).
• ?foo to backward search for term foo (also works with regular expressions).
• n to jump to next search result, N to jump to previous search result.
• :%s/foo/bar/g to substitute (s) all occurences (g) in the file (%) of "foo" with "bar".

screen

• Terminal multiplexer

  Happy little camper if connection to remote host breaks.

• Default configuration kind of sucks

  Get a good .screenrc file with a proper status line.

• caption always "%{= kw}%-w%{= BW}%n %t%{-}%+w %-= %c"

• Alternatives

  • tmux - screen done right?
  • Byobu - user-friendly wrapper around screen.

screen - command parameters

• screen -ls to list running screen sessions.
• screen -r to reattach to running screen session.
• screen -x to reattach to already attached screen session (Multi display mode).
• screen -dmS foo to create a detached screen session named "foo".
• screen -wipe to remove dead screen descriptors.

screen - keyboard shortcuts

• Ctrl-A c to create a new screen.
• Ctrl-A n or Ctrl-A Space to move to next screen in list.
• Ctrl-A p to move to previous screen in list.
• Ctrl-A Ctrl-A to move to previously active screen.
• Ctrl-A [0-9] to move to given screen in list.
• Ctrl-A " to show a list of running screens.
• Ctrl-A A to rename current screen.
• Ctrl-A k to kill current screen.
• Ctrl-A S to horizontally split current region.
• Ctrl-A | to vertically split current region.
• Ctrl-A Tab to switch to next region.

Thanks for listening!

Any questions?

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