Linux

Front 1

Searching for text inside a file

Back 1

grep pattern file

To invert the match: grep -v pattern file

Front 2

grep options

Back 2

-i search ignoring case

-c number of occurrences

-n precede output with line numbers

Front 3

List directories no contents

Back 3

ls -ld

ls -d

Front 4

Go to the previous directory

Back 4

cd -

cd $OLDPWD

Front 5

Symbols for users

Back 5

$ normal user

# super user

Front 6

Symlink

Back 6

Symbolic link

Points to the location of the actual file or directory

Front 7

What user you are working as

Back 7

whoami

Front 8

Command to change permissions (modes)

Back 8

chmod - change mode

ugoa - the user category: user(owner) group others all

+ - = - add substract or set premissions

r w x - read write execute

$chmod g+w sales.data

$chmod g-w sales.data

Front 9

Run the last command as root

Back 9

sudo !!

su -c "!!"

Front 10

Sort by time in reserve other

Back 10

ls -latr

Front 11

Comments

Back 11

#

Octofhorpe

Hash

Square

Pound sign

Number sign

Front 12

Listing files with color

Back 12

ls -F

ls --color

Front 13

Reuse the last word (last argument) from the previous command

Back 13

!$

$unzip tspreport.zip

$rm !$

Front 14

Reuse the nth word from a previous command

Back 14

$!!:N

$avconv -i screencast.mp4 podcast.mp3

$mv !!:2 converted/

Front 15

Reuse the second word (first argument) from the previous command

Back 15

!^

Front 16

Event designator

Back 16

!u most recent that starts with u

References a command in your shell history.

Front 17

Line continuation character

Back 17

\

Front 18

Sudo

Back 18

Superuse do

Front 19

Viewing files in real time

Back 19

tail -f file

Front 20

Find files by index

Back 20

To know where a file resides.

locate pattern

$locate tpsrep

Query the index or.database created by updatedb and not looking at each file. Index is not in real time.

Front 21

Cut file

Back 21

cut out selected portions of file. If a file is omitted, use standard input.

cut -d delimiter : Use delimiter as a file separator.

cut -f N : Display the nth field

$strings bluetraim.mp3 | grep -i john | head -1 |cut -d ' ' - f 2

Front 22

man command

Back 22

help: type h while viewing a manual page.

Enter: move down one line.

Space: move down one page

g: move to the top of the page

G: move to the bottom of the page.

q: quit

Front 23

Environment variable

Back 23

Storage location that has a name an a value. Ex: PATH

Front 24

Search pattern to delete multiple files at once

Back 24

ls s* check

rm s*

ls -d .*

rm .*

Front 25

Null device

Back 25

/dev/null To ignore output. Special file that throws away whatever is fed to it. (bit bucket). If.you do not want to see errors on your screen and you do not want to save them to a file, you can redirected them to /dev/null $ls here not-here 2> /dev/null here

Front 26

groups

Back 26

To see what.groups you are a member of.

If you supply another users id as an argument you will see.the list of groups to which that user belongs.

$groups

$id -Gn

$groups moniccon

Front 27

read, write and execute numbers modes

Back 27

0 ---

1 --x

2 -w-

3 -wx

4 r--

5 r-x

6 rw-

7 rwx

chmod 754 file

Front 28

ls first character

Back 28

- regular file

d directory

l symbolic link

Front 29

Permissions

Back 29

r read

w write

x execute (when d it allows access to contents and metadata for entries in the directory)

Front 30

Category of users

Back 30

u user

g group

o other

a all

Every user is member of at least one group called their primary group.

Front 31

Transferring and copying files

Back 31

scp secure copy

Sftp ssh file transfer protocol (filezilla)

$scp source dest

$sftp username@host : connect to host as username to begin a secure transfer session.

Front 32

Outputs redirections

Back 32

> to redirect output

< to redirect input

>> redirects standard output to a file and appends to any existing contents. If no file exists it creates one.

$ls -lF /opt/apache > files.txt

$sort < files.txt

$sort < files.txt > sortedfiles.txt

$ls here not-here 1> out 2> out.err

Front 33

PATH

Back 33

Environment variable that contains a lost of directories that contain executable commands

Front 34

export | grep $SHELL

Back 34

Shows the shell that you are using

Front 35

ssh tunnel

Back 35

ssh -i key_location -p port_number user-name@server

Front 36

su [username]

Back 36

Change user id or become superuser.

Options:

- provide an environment similar to what the user would expect had the usser logged in directly.

-c command: specify a command to be executed.

If the command is more than one word in length, it needs to be quoted.

Front 37

yum

Back 37

yum remove package : remove/uninstall package

yum info [package] -display : information about a package

Front 38

ls

Back 38

ls: list directory contents.

cd [dir]: changes the current directory to dir. Without a dir.it navigates to home directory.

pwd: displays the present working directory name.

cat [file] : concatenates and displays files to view contents of a file

Front 39

Directories symbols

Back 39

. This directory

.. The parent directory

/ directory separator. Directories end in a forward slash and this is often assumed.

Front 40

| pipes

Back 40

Means take the standard output from the preceding command and pass it as the standard input to the following command.

$strings bluetrain.mp3 | grep -i john

If the first command displays error messages those will not be passed to the second command. Those error messages are called "standard error" output.

$string bluetrain.mp3 | grep -i john |head -l

Front 41

| pipes

Back 41

$grep bob /etc/password |less

$ls -l /usr/bin/ | less

$ps -ef | more

Front 42

$EDITOR

Back 42

Environment variable that has which program to use for editing.

crontab -e

invokes the editor specified by the $EDITOR environment variable.