Special Environment variables
<<<< ^^^^^ >>>>

  •  Called "special parameters" in the bash man page
  • $0 The name of the script file (like argv[0] in C)
    $1, $2, ... The positional arguments (like argv[1], argv[2]... in C)
    $@ Expands to a string containing all positional arguments (but not $0), separated by spaces.
    $# The number of arguments (not counting $0). Similar to argc in C.
    $$ The process ID of the running script (not of the calling process).
    $? The exit status (return value) of the last foreground process. This is used to test the return value of programs run from the script.
    $(command) Expands to the stdout output by the command in the parens. Note that the same effect can be produced by surrounding the command with backticks, but that syntax is becoming depreciated.

    <<<< ^^^^^ >>>>

    Copyright (C) 2005 by Steve Litt, you can freely distribute unmodified copies if this copyright notice and disclaimer are intact.  This material originally appeared on Troubleshooters.Com.

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