I2rda Course Cheatsheet

Command-line Navigation

• ctrl + a: go to beginning of line
• ctrl + e: go to end of line
• ctrl + w: delete current word backwards, word behind if in space
• ctrl + /: undo changes
• ctrl + x, <BACKSPACE>: search backwards for a character, here?
• ctrl + r, ?: search backwards for a character, here?
• alt + b: move backwards word-wise.
• alt + f: move backwards word-wise
• alt + d: delete current word forwards, next word if in space
• ctrl + k: delete to end of line

Pagers: man, less and vim keys

• This is a continuous and very important activity
• Linux has a large and comprehensive documentation system called man
• Linux manual pages are referred to as man pages.
• To open the man page for a particular command, you just need to type man followed by the name of the command you are interested in.
• To browse through a man page, use the up,down,pgup and pgn keys.
• To close (quit) the man page simply hit the q key on your keyboard.

followed by the type of thing you are trying to do. An example of this is in exercise 1-3, part c).

Exercise

• Look up the manual information for the ls command by typing the following in a terminal:

man echo
man mkdir

• What can you say about this command?

Now try:

man ls

• Did you think you knew this command already?
• What does the -h option do? What about the -a option? What would running ls -lrt do?
• Press the q key when you want to quit reading the man page.
• Try running ls using some of the options mentioned above.

• Look up some programs with man pages with the keywords "list directory"

man –k "list directory"

Linux shortcut symbols

• . the directory you are currently in, often used with mv, cp or ln -s to mean "in here please"
• .. the directory one level above the one you are currently in, aka. the parent directory

- To change directory to the one above your are in: cd ..

• To returns to the last directory you were working in before this one: cd –
• On its own, cd bring you to your home directory
• ~ shorthand for your home directory, where all your data is kept.
• > directs output of one command into a file
• | often called the pipe operator: directs output of one command into another command.

Keybindings for using the history file

• :<RET>: save command in history, do not execute.
• !$<RET>: the final argument of the last command
• !!<RET>: the entire last command
• !:1-$<RET>: everthing except the first word of the last command
• !$<RET>: the final argument of the last command
• ^then^now<RET>: replace the first occurence of then in last command with now
• !!:gs/then/now/<RET>: replace the ALL occurences of "then" in last command with "now"
• !!:gs/then/now/:p<RET>: as above except do not execute.

An important note on line endings – CR and LF

• Besides spaces in filename, there is another major pitfalls when transferring file over to Linux.
• In Linux, the end of line is called a new line, symbol with \n.
• Windows uses CR and LF .. called the DOS format.
• Old Macs used LF
• the tools dos2unix and mac2unix convert

Text editing

• There are very many text editors, but one of the most powerful and dependable is vi.
• It has a steep but tiny learning curve, which we hope to conquer in this section.

• "vi" is an old version and is available on all Unix/linux systems by default
• Vim is the modern version, it used ncurses to use the whole screen
• It's free and has graphical version call gvim and a Windows version too.

Using vim

• type vim to get in, and :q! to get out without saving.
• ZZ to save onto to current filename. ":sav fname" otherwise
• It opens in "normal" mode which is similar to less, in that direct editing is not expected.
• This is changed by pressing i. To get back to normal mode, press the ESC key.
• In normal mode u undoes any changes
• : while in normal mode allows command sto be entered
• Visual: enabled by "v" or "V" (visual block), sub-box at the bottom open.
• After v or V, movement keys ":%" will operate on whole document, ":’a,’b" operate between two marks, ":42,45" between two line numbers
• search via "/", ":set hlsearch" to see all the hits

Getting by in only normal mode

• movement keys, "w" jump via start of words; "e" jump via ends; "fc" jump to next c
• "0" for start of line, "A" for end of line and into insert mode
• "x" delete current character, "xp" switch positions of current and next character
• "yyp" copy current line and paste it underneath
• "dd" delete line, "2d" delete this and following two lines. "dgg" delete to start, "dG" delete to end
• "dw" delete current word
• Command: Activated by ":", sub-box at the bottom open, rich command language
• Visual: Activated by "v" or "V" (visual block), sub-box at the bottom open, rich command language

Advanced but really useful commands

• ":colorscheme desert" chang to the desert colour scheme, "morning" "delek" many others
• :%s/snooze/sneeze/gc also works
• :g/sneeze/d delete all lines without sneeze"
• :v/sneeze/d delete all lines with sneeze"
• ":42y[RET]p" paste line 42
• "d214G" delete to line 214
• "y214G" delete to line 214
• :set list, all non-printing characters are also shown.
• :set hlsearch, will highlight all search occurences.
• :set nu, show line numbers.

Exercises

Type:

screen

Then:

• ctrl+l, n: cycle through screen windows
• ctrl+l, :hardcopy RET: create a file with a copy of all inputs and outputs of your session.
• ctrl+l, d: detach screen session
• type screen -r to recover a detached
• type exit to get out of your screen sessions