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72 Cards in this Set
- Front
- Back
Shell File Order
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/etc/profile .bash_profile .bashrc /etc/bashrc
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Nonlogin shells
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/etc/bashrc, .bashrc
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bash
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knows what a function is
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Path can go anywhere
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True
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Set Path
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PATH=$PATH:$HOME:/whatever
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.(Dot) or source
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will run a file
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()
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Subshell
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$()
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Command substitution
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(())
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Arithmetic evauluation used when the value includes an equal sign.
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$(())
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Arithmetic expansion not for use with an equal sign.
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[]
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test command
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[[]]
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conditional expression adds string comparisons.
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File descriptors
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the place a program sends its output too and gets its input from.
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0
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Standard input
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1
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standard output
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2
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standard error
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>
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shorthand for 1>
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<
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shorthand for 0<
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< filename
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redirects standard input from filename
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> filename
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redirects standard output to filename. unless filename exists and no clobbber is set. If its not set it creates the file.
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>| filename
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redirects standard output even if no clobber is set and the file exists.
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>>
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redirects and appends standard output.unless filename exists and no clobber is set.
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<&m
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Duplicates standard from file descriptor m
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[n]>&m
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Duplicates standard output or file descriptor n if specified from the file descriptor m?
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[n]<&-
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closes standard input or file descriptor n if specified
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[n]>&-
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Closes standard output or file descriptor n if specified.
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#!
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Specifies a shell
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#
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begins a comment
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fork
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to create a process
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exec
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execute the command
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;
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separates commands
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You do not need
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whitespace
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\
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continues a command on the next line
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&
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backgrounds a process
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( )
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groups commands.
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jobs
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lists jobs
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fg
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brings a job to the foreground can also use a %
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bg
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sends a job to the background
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control d
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end of file
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dirs
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displays the contents of the directory stack
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pushd
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pushes a directory to the stack
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popd
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pops a directory off the stack.
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unset
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removes a variable
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readonly
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makes the value of a variable permanent
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declare and typeset
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set attributes and values for shell variables
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declare -a
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declares a variable as an array
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declare -f
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declares a variables to be a function name
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declare -i
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declares a variable to be of type integer
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declare -r
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makes a variable readonly
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declare -x
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exports a variable
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~
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home
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mail
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usually stored in /var/spool/mail/name
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PS1
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primary user prompt
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$
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prompt / user
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#
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root
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PS2
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User prompt ( Secondary )
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PS3
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Menu prompt
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PS4
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Debugging prompt
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IFS
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Internal Field seperator, seperates input fields
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fc
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displays edis and reexecutes commands.
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fc-l
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displays the 16 most recent commands.
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!
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starts a history event
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!!
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the previous command
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!string
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most recent command that started with that sting
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!#
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current command
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Alias
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a short name that the shell translates into a longer name or complex command.
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"" "" quotes
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litteral
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' '
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non litteral
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set -o noclobber
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turns on
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set +o noclobber
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turns off
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0 =
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True
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1 =
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False
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