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File system Root
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/ - top of file hierarchy
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Path
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either absolute or relative
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pwd
|
present working directory
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cd
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change directory
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~
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indicates home directory
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..
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moving up to folder above current
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.
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current folder
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ls
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lists all
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ls -F
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lists only folders
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ls -l
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show details
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ls -a
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show hidden files
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ls -al
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show hidden files + details
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mkdir
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creates folders
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rmdir
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removes folders
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cp
|
copy
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mv
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move; can also be used to rename a file
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rm
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remove command
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-i
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adds interactivity; warning if will delete an existing file
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ls -al
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10 charactesr; (1)file type + (9)file permissions
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rwx
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read, write, execute
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owner, group, world
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order which permissions are displayed
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r
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4 - indicates read permission
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w
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2 - indicates write permission
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x
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1 - indicates execute permission
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r-x
|
read and execute (5)
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755
|
rwe-er-er
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IF/THEN
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if [ <condition> ] then <commands> fi
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fi
|
terminates IF/THEN
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if_[_<equation>_]
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|
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-eq
|
is equal to (integer)
|
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-ne
|
is not equal to (integer)
|
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-gt
|
greater than (integer)
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-lt
|
less than (integer)
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-ge
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greater than or equal to (integer)
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-le
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less than or equal to (integer)
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=
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is equal to (string)
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!=
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is not equal to (string)
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ELIF
|
alternative to nested-if statements
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read
|
reads user input
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bash <directory> <variables>
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remember to put variables at end if variables are needed for command
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grep <word>
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print lines matching a pattern
|
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redirect operator
|
(>) send output to file instead of displaying on screen
|
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append operator
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(>>) appends data instead of displaying on screen
|
|
cut -d" "
|
cut empty columns
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cut -d, -f1,2,4
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cuts out only columns 1,2,4
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|
sort
|
sorts alphabetically
|
|
sort -n
|
sorts numerically
|
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uniq
|
removes duplicate lines from a text file; MUST BE SORTED FORT
|
|
tr "abc" "xyz"
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subsitute <v1> to <v2>
|
|
tr "[:lower:]""[:upper:]"
|
specify all lowercase letters to turn uppercase
|
|
new variable
|
supply variable name and its value; no spaces inbetween
|
|
variable1=2
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valid; no spaces between equals
|
|
$((<equation>))
|
arithmetic expansion
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echo $<variable>
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prints <variable value>
|
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" "
|
does not affect use
|
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' '
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used literally, does not call variables
|
|
$USER
|
lists current user
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$PWD
|
prints present working directory
|
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$HOME
|
home directory of current user
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$RANDOM
|
o and 32767
|
|
sleep #
|
sleeps for # seconds
|
|
find
|
search for files
|
|
find [where to start searching from][expression to fine][-options][what to find]
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takes 2 arguements; where to search & what to find; wildcards can be used
|
|
find /home -user alice -empty
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finds files in the home folder from alice which are empty
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Wildcards
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|
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?
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matches a single character
|
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*
|
matches any zero or more characters
|
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[x..y]
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matches a range of letters or numbers
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Examples
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|
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ls
|
lists all files + extensions
|
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ls *.doc
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lists only files with .doc extensions
|
|
re - r <target>
|
removes folders with content; be very careful
|
|
while
|
run until a specific conditions is met
|
|
CTRL+C
|
to close script
|
|
vim "filename"
|
starts up in command mode
|
|
i
|
insert mode - start typing
|
|
:w
|
write
|
|
:q
|
quit vim type
|
|
:wp
|
save and quit
|
|
:q!
|
quit w/o saving
|
|
/word
|
search towards end of file for first occurance of word
|
|
?word
|
search towards beginning of the file for the word
|
|
n
|
search for next occurance
|
|
N
|
search for previous occurance
|
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less
|
view file contents one screen at a time
|
|
head
|
top of file to see if it is the one you need
|
|
head -3
|
show the first three results
|
|
tail
|
bottom of file to see new log entries
|
|
-n
|
default output of ten line
|
|
-n#
|
changes number of lines outputed
|
|
-n & -n#
|
to be used with head or tail
|
|
YUM
|
|
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YUM
|
yellowdog updater modifier - package modifier
|
|
chmod
|
updates permissions on files and folders
|
|
su
|
grants super user privileges
|
|
ls -laF
|
lists all folders + access
|
|
chmod 775 engineering
|
changes permissions for the engineering folders
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|
chown
|
change ownership
|
|
chgrp
|
change group
|
|
chown dave README
|
changes owner of README to dave
|
|
chgrp sales_grp README
|
changes the group that can access README to sales_grp
|
|
aescrypt
|
secret key encryption
|
|
-e
|
encrypt the file
|
|
-d
|
decrypt the file
|
|
-p <password>
|
password to use; if omitted, the command will prompt the user
|
|
-o <filename>
|
output file
|
|
md5sum
|
easy way to generate a checksum
|
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#! /bin/bash
|
turns list of commands into one command // no need for bash ...
|
|
for var in <item/directory> do <commands> done
|
how to format for loops
|
|
Sequences
|
{#..#}
|
|
#..#
|
first # starting value .. second# ending value
|
|
#1..#2..#3
|
#3 is increment between each number series
|
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Cheatography n. The art of mapping complex subjects into clear, instantly navigable reference guides.
