Bash Commands

Front 1

jobs

Back 1

to see what jobs are running in the background and to check on their status.

Front 2

&

Back 2

Add to the end of a command to run the command in the background.

Front 3

cut -d: -f1 /etc/passwd | sort | lp

Back 3

output the first field of the /etc/passwd file delimited by a :. Then, sort the out put, and after, send the contents to the printer.

Front 4

cat < file1 > file2

Back 4

this will act similarly to the "cp file1 file2" command if the "cp" is not working properly or is broken.

Front 5

uname -a

Back 5

to see all of the contents about the kernel and the OS

Front 6

sed '/^$/d' file1 > file2

Back 6

to delete all of the blank lines within a given file.

Front 7

ls -l $(which cp)

Back 7

to see all the long output for the "cp" command. Permissions, owner, group, size, creation date, location etc...

Front 8

echo $(ls)

Back 8

to output the "ls" command as an expression.

Front 9

echo {A..Z}

echo Number_{1..5}

echo a{A{1,2},B{3,4}}b

echo mkdir {2007..2009}-0{1..9}{2007..2009}-{10..12}

Back 9

A through Z, Number_1 through 5, aA1b aA2b aB3b aB4b, make a bunch or directories.

Front 10

diff

diff file2.txt file1.txt.old > txtdiff &

Back 10

Examines two files then outputs the differences to standard out.

Front 11

"Background Jobs"

Back 11

Output might be intertwined with other command output. Just because I run concurrent commands in the background doesn't mean they will execute faster. It might actually be a bit slower.

Front 12

nice

Back 12

This will cause the command to run at lower priority when executed, which means it will be give less resources as well. Give a lower priority by adding a numerical value to the command. Quote complex commands that follow the nice command.

Front 13

(

)

Back 13

Start and end a sub shell

Front 14

{

}

Back 14

Start and end a command block

Front 15

'

Back 15

Strong quote will treat everything, including the special characters, as text.

Front 16

"

Back 16

Weak quote will treat some of the special characters within the quotes as special characters.

Front 17

?

Back 17

single character wild card

Front 18

!

Back 18

Not what ever comes next in the set

Front 19

\ or backslash-escaping

Back 19

to change the meaning of a character. Fore example, if you are looking for a ! in a document you can precede it with a \!

Front 20

find . -name some-string

find . -name '*.c'

Back 20

- will search the directory that you are in for a given string. You can also search by user, file size, date last accessed, etc.

- Will search the current directory and sub sub ... for all files ending in .c

Front 21

Ctrl-m

Back 21

Acts the same as Enter.

Front 22

stty or stty all

Back 22

Check the key binds on Linux and BSD/Unix based systems

Front 23

ctrl-\

Back 23

Can be used if ctrl-c doesn't work

Front 24

ctrl-u

Back 24

Delete an entire command from the end of the the line. Or from the beginning of the line to the cursor location

Front 25

fc

Back 25

Fix command, I can alter a command using a text editor. Then, exit the editor and use then command in the terminal.

Front 26

ctrl-p

ctrl-n

esc->

Back 26

- Go back through history

- Go to the last command entered

- " "

Front 27

ctrl-r

Back 27

Will a reverse-i-search. I can then start typing something in the previous command and it will populate on the line.

Pressing ctrl-r again will search for the next occurrence etc etc.

If I have already done a search, hitting ctrl-r twice will go to the first string that I typed in History

Front 28

export PATH=$PATH:what/you/wanttoadd/to/the/path

Back 28

Adding something to you PATH env variable. Depending upon where the : is will determine if the added the end or the beginning of your path.

Front 29

cd ~username

Back 29

to go to the home directory of a particular user.

Front 30

esc /

Back 30

This command will complete only file names

Front 31

esc-c

esc-u

esc-l

esc-.

Back 31

- Capitalize word after point

- Change word after point to all capital

- Change word after point to all lower

- Insert last word in previous command line after point.

Front 32

!n

! string

!? string

^ string1^string2

Back 32

- If you remember the line number of the command you are looking for.

- Refers to the most resent command starting with "string"

- The most resent command ending in string

- Repeat the last command, replacing string1 with stirng2

Front 33

Word designators:

0

n

^

$

Back 33

- Zeroth (first) word in a line

- The nth word in a line

- The first argument (the second word)

- The last argument in a line

Front 34

Designators Cont...

%

x-y

*

x*

x-

Back 34

- The word matched by the most recent ?string search

- A range of words from x to y. -y is synonymous with 0-y

- All words but the zeroth; synonymous with 1-$.; if there is only one word on the line, an empty string is returned.

- Synonymous with x-$

- The words from x to the second to las word

Front 35

word designator : event designator

!!:0

Back 35

Repeat the previous command with different arguments by typing !!:0 followed by the new arguments

Front 36

Modifiers (can follow designators, multiple modifiers can be used separated by a :)

h

r

e

t

Back 36

- Removes a trailing pathname component, leaving the head.

- Removes the trailing suffix of a form .xxx

- Removes all but the trailing suffix

- Removes all leading pathname components, leaving the tail.

Front 37

Modifiers cont...

p

q

x

s/old/new/

Back 37

- Prints the resulting command but doesn't execute it.

- Quotes the substituted words, escaping further substitutions.

- Quotes the substituted words, breaking them into words at blanks and newlines

- Substitute the new with the old.

Front 38

Options:

noclobber

Back 38

- The - turns the option on and the + turns it off. "set -o <option> -"

- Want let you > to existing file

Front 39

shopt

Back 39

- used for editing environmental variables, vary similar to options.

-s to turn on

-u to turn off

Front 40

Shell Variables

Back 40

- varname=value

- Must be all caps

- If the value is more than one word must be in quotes

- "$aaa" if there are added spaces in the string that way bash will treat it like one word.

Front 41

HISTCMD

HISTFILESIZE

HISTSIZE

HISTCONTROL

HISTIGNORE

HISTTIMEFORMAT

Back 41

-

-

-

- can use to control what shows in history, such as excluding cmds starting with spaces and repeated commands. ignorespace, ignoreups

- If a pattern is met, it is not recorded in history. & will ignore duplicates.

-

Front 42

Mail Variables:

MAIL or MAILPATH (list of files)

MAILCHECK

Back 42

- name of file to check for incoming

- how often to check

Front 43

command precedence

Back 43

1. Aliases

2. Key words like function and several others, like if or for.

3. Functions

4. Built-ins like cd and ls

5. Scripts and executables, for which the shell searches in the directories listed in the PATH env var