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#
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Super User
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$
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normal user
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date
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display current date and time
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cal
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display current month calendar
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df
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displays disk usages
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free
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display memory usage
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cd
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change the current diretcory
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ls
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list the directory
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file
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Determine file type
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less
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view file contents
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cp
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copy the files
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mv
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move the files from one folder to other
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mkdir
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creates a directory
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rm
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remove files and directories
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ln
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create Hard and symbolic link
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i
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interactive
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same in mv
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a
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copy files and directories of all attributes, ownership and permission
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-
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r
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recursively copies directories and contents
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same in mv
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u
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copy the files that don't exists
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same in mv
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v
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verbose, informative message
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same in mv
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echo $(ls)
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ls -l $(which cp)
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new method
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ls -l
which cp |
back tick, old method
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ps
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reports snap shot of current process
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top
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diskplays task
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jobs
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list active jobs
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bg
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place a job in the background
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fg
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place a job in the foreground
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kill
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send a signal to process
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killall
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kill process by name
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ps aux
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BSD style ouptut
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fg %1
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jobs
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kill -1 13456
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kill process id 13456
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ps -eo pid,comm,cmd,start,etime
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to get process elapsed time
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cmin
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match attributes/files/dir modified, n minutes
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cnewer
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match file/dir whose content or attribute were last modified n*24 ago
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ctime n
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match file or direct whose content or attribute were modified n*24 hrs ago
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empty
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match empty files and directories
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group name
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match files or direc belonging to group name
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iname
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pattern like the iname test but case insensitive
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inum n
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match files with inode number
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mmin n
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match files or dir whose content were modified n minutes ago
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mtime n
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match files or dir whose content were modified n*24 hours ago
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name pattern
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match files and dir with specified wildcard pattern
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nouser
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match files and dir that don't belong to valid user
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nogroup
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match files and dir that don't belong to valid group
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perm mode
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match files and directories set to specified mode
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samefile name
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matches files that share the same inode number as file name
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size n
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match file size of n
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type c
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match file type of c
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user
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match file and directories belong to user
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and
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or
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not
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delete
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ls
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print
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quite
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depth
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to process a directory files before the dir itself
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maxdepth
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max num of level that find will descend into a directory when performing test and action
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mindepth
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min num of level that find will descend into a directory when performing test and action
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mount
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direct find not to traverse directories that mounter on other filesystem
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clear
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clears the screen
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history
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stores the history
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script file
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capture all command execution in a file
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type
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Indicate how command name is interpreted
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which
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display which executable program will be executed
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man
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Display manual page
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apropos
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Display appropriate command
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info
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Display command Info entry
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whatis
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Display brief description of command
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alias
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create an alias for command
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dmidecode
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provides valueable inisights into system hardware configuration
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lscpu
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provides detailed information about cpu
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1
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User commands
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2
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Programming interface for system calls
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3
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Programming interface for C Library
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4
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Special files such devies nodes and drivers
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5
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file formats
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6
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Games and screen savers
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7
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misc
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8
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system administrator commands
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cat
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concatenates files
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sort
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sort the file
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uniq
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report or omit repeated lines
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grep
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print lines matching pattern
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head
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prints first few lines of file
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tail
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prints las few lines of file
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tee
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reads stdin and send output to stdout and file
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wc
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count number of line, words, and bytes
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ls -l /usr/bin >file
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default stdout to file
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ls -l /usr/bin 2>file
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redirects stderr to file
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ls -l /usr/bin > ls-output 2>&1
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redirects stderr & stdout to file
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ls -l /usr/bin &> ls-output
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redirects stderr & stdout to file
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ls -l /usr/bin 2> /dev/null
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/dev/null bitbucket
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pipelines
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ls -l /usr/bin/ | tee out | sort
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tee reads stdin and writes to files and stdout
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echo *
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expands all files in the path
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echo D*
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expands all files with starting D
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$((expression))
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Arithematic expression
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echo $(($((5*2))3))
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75
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ls -l
which cp |
backtick instead of expression
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echo Front-{A,B,C}-Back
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Front-A-Back, Front-B-Back, Front-C-Back
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echo {Z..A}
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Z Y X W V U .....A
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mkdir {2009..2011}-0{1..9} {2009..2011}-{10..12}
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creates a directory for 12 months in 2009 to 2011
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printenv
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Print part of all of the environment
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set
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set shell options
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export
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export environment to subsequently executed programs
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alias
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create an alias for command
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echo This is a test
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This is a test; space is stripped
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echo "This is a test"
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This is a test
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echo '$(echo foo) $((2+2))'
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$(echo foo) $((2+2))
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echo the total is $500.00
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$5 is undefined variable so it supress the value, output will be like the total is 00.00
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locate
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find files by name
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find
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search for files in a dir
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xargs
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build and exec cmd lines from stdin
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touch
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change the file times
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stat
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display file or filesystem status
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Ping
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Send ICMP packets
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traceroute
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Print route packets to a network
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netstat
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print network connection, routing table, interface stats
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ftp/lftp
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Internet file transfer program
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wget
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Non Interactive network downloader
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ssh
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OpenSSH SSH Client (remote login program)
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scp
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secure copy
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sftp
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Secure File transfer program
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gzip
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Compress or expand files
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bzip2
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A block sorting file compressor
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tap
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tape archving utility
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zip
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Package and compress files
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rsync
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remote file and dir synchronization
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unzip
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Unzip the gzip files
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cat -A $FILE
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To find any CTRL character introduced
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sort file1.txt file2.txt file3.txt > final_sorted_list.txt
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sort all files once
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ls - l | sort -nr -k 5
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key field 5th column
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sort --key=1,1 --key=2n distor.txt
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key field 1,1 sort and second column sort by numeric
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sort foo.txt | uniq -c
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to find repetition
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cut -f 3 distro.txt
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cut column 3
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cut -c 7-10
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cut character 7 - 10
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cut -d ':' -f 1 /etc/password
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delimiter :
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sort -k 3.7nbr -k 3.1nbr -k 3.4nbr distro.txt
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3 rd field 7 the character, 3rd field 1 character
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paste file1.txt file2.txt > newfile.txt
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merge two files
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join file1.txt file2.txt
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join on common two fields
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cat
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concatenate files and print stdout
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sort
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sort lines of text files
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uniq
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report or omite repeated lines
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cut
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remove section from each line of files
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paste
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merge lines of files
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join
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join lines of two files on a common field
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comm
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compare two sorted files line by line
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diff
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compare files
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patch
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apply a diff file to original
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tr
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translate
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sed
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stream editor
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aspel
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interactive spell checker
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id
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display user identity
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chmod
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change's file mode
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umask
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set the default file permission
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su
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Run a shell as another user
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sudo
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Execute command as another user
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chown
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changes file's owner
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chgrp
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change file groups owner
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passwd
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change a user password
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- | rwx | rw- | r--
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type | owner | group | world
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000
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---
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001
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--x
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010
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-w-
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011
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-wx
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100
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r--
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101
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r-x
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110
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rw-
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111
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rwx
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ugo
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user, group, others
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u+x
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giving exeute permission for user
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u=rw,o=x
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giveing user read write and others execute perm
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Debian Style (.dep)
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Debain, ubuntu, xandros, Linspire
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RedHat style(.rpm)
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Fedora, CentOS, Redhat Enterprise, OpenSUSE, Mandriva, PCLinuxOS
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debian
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apt-get install package_name
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redhat
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yum install package_name
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mount
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mount a filesystem
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ummount
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unmount a file system
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fdisk
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partition table manipulator
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fsck
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check and repair filesystem
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fdformat
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format floppy disk
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mkfs
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create a file system
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dd
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write a block oriented data directly to a device
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genisoimage
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create an ISO 9660 image file
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wodim
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Write data to optical storage device
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md5sum
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calculate md5sum
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i
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ignore case
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v
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invert match
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c
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print number of matches
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l
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print the name of each file that contain matches
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L
|
print only the names of files that don't match
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n
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print match line with the number
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h
|
for multiple output supress the output of filename
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grep -h '.zip' file.list
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. is any character
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grep -h '^zip' file.list
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starts with zip
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grep -h 'zip$' file.list
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ends with zip
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grep -h '^zip$' file.list
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containing only zip
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grep -h '[^bz]zip' file.list
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not containing b and z
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grep -h '^[A-Za-z0-9]' file.list
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file containing any valid names
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?
|
match element zero or one time
|
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*
|
match an element zero or more times
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+
|
Match an element one or more times
|
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{}
|
match an element specfic number of times
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diff -c
|
context format
|
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diff -u
|
unified format
|
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diff -Naur oldfile newfile > diff_file
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write the diff to diff file
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patch < diff_file
|
applied to oldfile directly.
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echo "secret text" | tr a-zA-Z n-za-mN-ZA-M
|
frperg grkg | ROT13 Encoding
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echo "frperg grkg" | tr a-zA-Z n-za-mN-ZA-M
|
secret text | ROT13 Decoding
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Backup of superblock
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dumpe2fs /dev/sdX | grep -i superblock
|
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Restore of superblock
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fsck -b 32768 /dev/sdX
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dumps ext2/ext3/ext4 filesystem info including inode locations
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dumpe2fs /dev/sdX
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interactive tool to inspect inodes
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debugfs /dev/sdX
|
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shows inode number and metadata
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stat filename
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