Control Flow

Control flow statements direct execution based on conditions and iteration.

Source: src/scripting/control_flow.f90, src/ast/evaluator_simple_real.f90

Overview

fortsh supports all standard shell control flow constructs:

• Conditionals - if/elif/else/fi and case/esac
• Loops - for, while, until
• Functions - Named command groups with local scope

Quick Reference

Conditionals

if [[ $x -gt 0 ]]; then
    echo "positive"
elif [[ $x -lt 0 ]]; then
    echo "negative"
else
    echo "zero"
fi

Case Statements

case $input in
    y|yes) echo "Confirmed" ;;
    n|no)  echo "Cancelled" ;;
    *)     echo "Unknown" ;;
esac

Loops

# Word list
for file in *.txt; do
    echo "$file"
done

# C-style arithmetic
for ((i=0; i<10; i++)); do
    echo $i
done

# While
while read line; do
    echo "$line"
done < file.txt

Functions

greet() {
    local name="$1"
    echo "Hello, $name"
}

greet "World"

Exit Status

Control flow keywords (if, while, done, etc.) reset the exit status to 0 after condition evaluation, per POSIX specification.

The exit status of:

• if/elif/else/fi - status of last executed command
• case/esac - status of last executed command, or 0 if no pattern matched
• for/while/until - status of last executed command, or 0 if body never executed
• Functions - status of last command or explicit return value

Operators