bash.txt

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BASH

$0             - Name of the script itself
$1, $2, etc.   - Positional parameters
$*             - Positional parameters as a single word (within double quotes)
$@             - Positional parameters as separate words (within double quotes)
$#             - Number of positional parameters
$?             - Exit status of the most recently executed command
$$             - Process ID of the shell

${1//[0-9]/}   - Removes all digits from $1
${1//[!0-9]/}  - Removes all except digits from $1

DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
  // Gets the script's source file pathname, strips it to just the path portion,
  // cds to that path, then uses pwd to return the (effectively) full path of
  // the script.


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CONDITIONAL ACTIONS

rm foobar && echo "Success"
rm foobar || echo "Fail"
rm foobar && echo "Success" || echo "Fail"


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EXAMPLES:

if [[ -z "$@" ]]; then
  echo "Need arguments like: alfa1"
  exit 1
fi

if [[ $1 == alpha* ]]; then
  echo "ALPHA"
elif [[ $1 == beta* ]]; then
  echo "BETA"
else
  echo "Failed to detect alpha/beta"
  exit 1
fi