Lab46 Wiki

Rejoining class chat Most of you probably already know this but I thought I would throw it on here for quick reference. So to join a class chat session do:

$screen irssi
/server irc
/join nameOfYourCouse

Using vi/vim

• This is not classic vi it's vim.
• The esc key will get you back to command mode.
• vi - is a moded text editor
  • command: symbols are commands
  • input: symbols are input

1. i this will put you into input mode. (This will place characters before the courser.
2. a this will insert after the courser.
3. I this will insert at the beginning of the line
4. A this will insert at the end of a the line.
5. o this will start on the next line.
6. O this will start you on the line before.
7. Navigation
   1. h go left
   2. l go right
   3. j down
   4. k up
   5. w right by word
   6. b left by word
   7. {} these jump up and down by stanza
8. Manipulation
   1. X remove character left (cut)
   2. x remove character right (cut)
   3. p place to the left of cursor (paste)
   4. P place to the right of cursor (paste)
   5. . this will run the last command
9. How to save from vi - in command mode hit : then w then fileName (:w myFile)
10. How to leave the vi text editor
    1. :wq - save and quit
    2. :w - name save as
    3. :q - quit
    4. :q! - with without saving

Viewing files in a directory with Wildcards

• ls -a - This will list hidden files. If you use the -A this will remove the extra information.
• ls -1 - This will list the files that a normal ls would give you but it will list them with one file per line.
• ls -1 ???? - This will list only the files in your current directory that have 4 characters. Similarly if you use 5 ?s it would list the files with 5 characters.
• ls | wc -l - The wc -l part of the command counts the entries.
• ls -1 c??? - This will give all the 4 character files that begin with c. If you wanted to see the ones with uppercase C as well you can use a character class like : [cC]???
• ls -1 ?[aeiou]?[aeiou]? - This command looks very complicated but it is simply giving us the 5 character file names which have vowels in the 2nd and 4th character place.
• ls -1 ????* - This shows the files which have 4 or more characters.
• ls -1 *p - This will show all the files that begin with “p”
• ls -1 *hi* - This searches for any and all files that have the characters “hi” in them.
• file * - This command will show the file information for every in the current directory.

Wildcards

• * - match 0 or more of anything.
• ? - match exactly 1 of anything.
• [] - Character class match any 1 of the enclosed
• [^ ] - inverted characters class, do not match any 1 of enclosed.
• If it accepts a file you can use a wild card in its place.

Some basic scripting stuff and cool commands…

* If you would like to use a command but need to have a “-something” the “-” would make the command try and use “something” as an argument. So if you need to have a “-” in something you need in a command you can use – to negate the later “-”. An example of this: grep -q – '-greppingForThis'

• If you want to print out the debugging information for a file you use the #!/bin/bash -x we all probably know this. But if you would like to add it as a argument to your script you can use: set -o xtrace

• If you want to know the width of the screen your running on (or in a script) use tput cols. The best way to use this (at least in a script) is probably to set it in a variable like this: var=$(tput cols) Then when you call the function it will come back with the screen width.

• A cool thing: If you want an error your printing to standard standard error just redirect standard input into standard error by doing 1>&2

• « If you want to compose a file on the command line do:

$ cat <<name
>stuff here.
>More things.
>name

• A couple notes: whatever you put after the “«” in this case “name” also needs to end the command line (see above).
• This is called a “here file”

• «< - a “here string.” This will simply basically echo what comes after like:

$ cat <<< "Stuff"
Stuff

• When doing a “exit” you can add an exit code like: exit 0 This is the one we usually use but if you do an exit 1 (or any other number). That tells the script to exit with a “1” This is really helpful when debugging and if you would like to view the exit code do “$?” on the command line..

• Something cool. If you would like to see your command history do: history
  • Then along the left side you can see the “history” number. You can use those numbers to call back specific commands. Like:

...
550 echo "hello"
551 echo "$test"
$ !550
hello