Conditionals in Bash

If statements

  • Conditional blocks start with if and end with the inversion fi (this is a common syntactic pattern in bash)
  • The conditional expression must be placed in square brackets with spaces either side. The spaces matter: if you omit them, the code will not run
  • We designate the code to run when the conditional is met with then
  • We can incorporate else if logic with elif

Basic example

if [ -e $var ]; then
  # Do something
else
  # Do something else
fi

If, else

if [ "$myMove" -eq "$opponentMove" ]; then
    (( totalScore+=myMove+3 ))
  elif [ $absDiff -eq 2 ] && [ "$myMove" -gt "$opponentMove" ]; then
    (( totalScore+=myMove))
  elif [ $absDiff -eq 2 ] && [ "$opponentMove" -gt "$myMove" ]; then
    (( totalScore+=myMove+6))
  elif [ $absDiff -eq 1 ] && [ "$opponentMove" -gt "$myMove" ]; then
    (( totalScore+=myMove))
  elif [ $absDiff -eq 1 ] && [ "$myMove" -gt "$opponentMove" ]; then
    (( totalScore+=myMove+6))
  fi

Nested conditionals

if [[ "$line" =~ ^$ ]]; then
  if [[ "$runningTotal" -gt "$highest" ]]; then
    (( highest=runningTotal ))
  fi
  # Reset running sum
  (( runningTotal=0 ))
fi
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