= Bash Logic =

<<TableOfContents>>

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== Conditional Logic ==

Any commands and grammars that set exit codes can be used for conditional logic.

{{{
if grep /path/to/file --fixed-strings foo >/dev/null; then
  :
fi
}}}

The `[[` builtin sets the exit code to 0 if a [[Bash/Test|test]] evaluates to true, and 1 otherwise.

{{{
if [[ TEST ]]; then
  :
fi
}}}

The `((` builtin sets the exit code to 0 if an arithmetic expression resolves to any non-zero number, and 1 otherwise. See [[Bash/Arithmetic|here]] for details on valid arithmetic.

{{{
if (( $var - 1 )); then
  :
fi
}}}

----



== Conditional Commands ==

To execute a command conditionally after another command, try:

{{{
true && echo "This only executes because the first command set an exit code of 0"

false || echo "This only executes because the first command set an exit code of 1"
}}}

These operators have equal precedence.

----



== Case Switching Logic ==

{{{
case $INPUT_STRING in
  y)
    echo "Proceeding..."
    ;;
  n)
    echo "Quitting..."
    ;;
  *)
    echo "Please enter y or n only"
    ;;
esac
}}}



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CategoryRicottone