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    The great GNU Bourne-Again Shell[edit]

    Bash is the shell, or command language interpreter, that will appear in the GNU Operating System.

    Bash is an sh-compatible shell that incorporates useful features from the Korn shell (ksh) and C shell (csh).

    Bash Links[edit]

    Useful Keyboard combinations in Bash[edit]

    With control (crtl)[edit]

    • crtl-a = start of line
    • crtl-e = end of line
    • crtl-l = clears the screen, like command clear
    • crtl-p = previous command from history, like page up key
    • crtl-r = reverse search in history(incremental)

    With escape(esc)[edit]

    • esc-f = one word forward
    • esc-b = one word backward

    Operators[edit]

    Assignment Operators[edit]

    =
    

    All-purpose assignment operator, which works for both arithmetic and string assignments.Do not confuse the "=" assignment operator with the = test operator.

    Arithmetic Operators[edit]

    +
    

    plus

    -
    

    minus

    *
    

    multiplication

    /
    

    division

    **
    

    exponentiation

    %
    

    modulo, or mod (returns the remainder of an integer division operation)

    +=
    

    "plus-equal" (increment variable by a constant). let "var += 5" results in var being incremented by 5.

    -=
    

    "minus-equal" (decrement variable by a constant)

    *=
    

    "times-equal" (multiply variable by a constant). let "var *= 4" results in var being multiplied by 4.

    /=
    

    "slash-equal" (divide variable by a constant)

    %=
    

    "mod-equal" (remainder of dividing variable by a constant)

    Logical Operators[edit]

    &&
    

    and (logical). if [ $condition1 ] && [ $condition2 ]

    ||
    

    or (logical). if [ $condition1 ] || [ $condition2 ]

    Dont confuse those with #Conditional executing.

    Comparison Operators[edit]

    Integers[edit]
    -eq
    

    is equal to. if [ "$a" -eq "$b" ]

    -ne
    

    is not equal to. if [ "$a" -ne "$b" ]

    -gt
    

    is greater than. if [ "$a" -gt "$b" ]

    -ge
    

    is greater than or equal to if. [ "$a" -ge "$b" ]

    -lt
    

    is less than. if [ "$a" -lt "$b" ]

    -le
    

    is less than or equal to. if [ "$a" -le "$b" ]

    <
    

    is less than. (within double parentheses) (("$a" < "$b"))

    <=
    

    is less than or equal to. (within double parentheses). (("$a" <= "$b"))

    >
    

    is greater than (within double parentheses). (("$a" > "$b"))

    >=
    

    is greater than or equal to (within double parentheses). (("$a" >= "$b"))


    Strings[edit]
    =
    

    is equal to. if [ "$a" = "$b" ]

    ==
    

    is equal to. if [ "$a" == "$b" ]

    !=
    

    is not equal to. if [ "$a" != "$b" ]

    <
    

    is less than, in ASCII alphabetical order

    >
    

    is greater than, in ASCII alphabetical order

    -z
    

    string is "null", that is, has zero length

    -n
    

    string is not "null".

    Bitwise Operators[edit]

    <<
    

    bitwise left shift (multiplies by 2 for each shift position)

    <<=
    

    "left-shift-equal" let "var <<= 2" results in var left-shifted 2 bits (multiplied by 4)

    >>
    

    bitwise right shift (divides by 2 for each shift position)

    >>=
    

    "right-shift-equal" (inverse of <<=)

    &
    

    bitwise and

    &=
    

    bitwise and-equal

    |
    

    bitwise OR

    |=
    

    bitwise OR-equal

    ~
    

    bitwise negate

    !
    

    bitwise NOT

    ^
    

    bitwise XOR

    ^=
    

    bitwise XOR-equal


    Misc Operators[edit]

    ,
    

    comma operator . The comma operator chains together two or more arithmetic operations. All the operations are evaluated (with possible side effects), but only the last operation is returned.

    Conditional executing[edit]

    command1 && command2
    

    command2 is executed if, and only if, command1 returns an exit status of zero. (exit status zero means succesful)

    command1 || command2
    

    command2 is executed if and only if command1 returns a non-zero exit status. (non-zero exit status means failed)

    command1 && command2 || command3 
    

    if command1 is executed successfully then shell will run command2 and if command1 is not successful then command3 is executed.

    Wildcards / regex[edit]

    These can be used on filenames.

    *
    

    zero or more characters

    ?
    

    exactly one character

    [abcde]
    

    exactly one character listed

    [a-e]
    

    exactly one character in the given range

    [!abcde]
    

    any character that is not listed

    [!a-e]
    

    any character that is not in the given range

    {debian,linux}
    

    exactly one entire word in the options given

    You can use wildcards with any command that accepts file names as arguments.

    also see: Bash Scripts

    <man>bash</man>

    Bash built-in commands[edit]

    GNU bash, version 2.05a.0(1)-release (i386-pc-linux-gnu)
    These shell commands are defined internally.  Type `help' to see this list.
    Type 'help name' to find out more about the function `name'.
    Use 'info bash' to find out more about the shell in general.
    
    A star (*) next to a name means that the command is disabled.
    
     %[DIGITS | WORD] [&]               . filename
     :                                  [ arg... ]
     alias [-p] [name[=value] ... ]     bg [job_spec]
     bind [-lpvsPVS] [-m keymap] [-f fi break [n]
     builtin [shell-builtin [arg ...]]  case WORD in [PATTERN [| PATTERN].
     cd [-PL] [dir]                     command [-pVv] command [arg ...]
     compgen [-abcdefgjkvu] [-o option] complete [-abcdefgjkvu] [-pr] [-o 
     continue [n]                       declare [-afFrxi] [-p] name[=value
     dirs [-clpv] [+N] [-N]             disown [-h] [-ar] [jobspec ...]
     echo [-neE] [arg ...]              enable [-pnds] [-a] [-f filename] 
     eval [arg ...]                     exec [-cl] [-a name] file [redirec
     exit [n]                           export [-nf] [name ...] or export 
     false                              fc [-e ename] [-nlr] [first] [last
     fg [job_spec]                      for NAME [in WORDS ... ;] do COMMA
     function NAME { COMMANDS ; } or NA getopts optstring name [arg]
     hash [-r] [-p pathname] [-t] [name help [-s] [pattern ...]
     history [-c] [-d offset] [n] or hi if COMMANDS; then COMMANDS; [ elif
     jobs [-lnprs] [jobspec ...] or job kill [-s sigspec | -n signum | -si
     let arg [arg ...]                  local name[=value] ...
     logout                             popd [+N | -N] [-n]
     printf format [arguments]          pushd [dir | +N | -N] [-n]
     pwd [-PL]                          read [-ers] [-t timeout] [-p promp
     readonly [-anf] [name ...] or read return [n]
     select NAME [in WORDS ... ;] do CO set [--abefhkmnptuvxBCHP] [-o opti
     shift [n]                          shopt [-pqsu] [-o long-option] opt
     source filename                    suspend [-f]
     test [expr]                        time [-p] PIPELINE
     times                              trap [arg] [signal_spec ...] or tr
     true                               type [-apt] name [name ...]
     typeset [-afFrxi] [-p] name[=value ulimit [-SHacdflmnpstuv] [limit]
     umask [-p] [-S] [mode]             unalias [-a] [name ...]
     unset [-f] [-v] [name ...]         until COMMANDS; do COMMANDS; done
     variables - Some variable names an wait [n]
     while COMMANDS; do COMMANDS; done  { COMMANDS ;
    

    use help <command>, f.e help shift to get more information about the commands.

    Bash on Mac OS X[edit]

    Bash on Windows[edit]

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