MirBSD Korn Shell

mksh

A free implementation of the Korn shell. Like bash, this is a superset of the Bourne Shell.

Hello World

#!/usr/bin/env mksh

print "Hello World!"

Coding Guide

Language Version

mksh (MirBSD Korn Shell) - Korn shell implementation

Execution Model

• Interpreted shell script
• Code executes directly from source
• Scripts run line-by-line from top to bottom
• Uses shebang #!/usr/bin/env mksh for execution
• Compatible with POSIX shell and extends Korn shell features

Key Characteristics

• Korn shell compatible (superset of Bourne Shell)
• Case-sensitive
• Variables: VAR=value (no spaces around =)
• Command substitution: `command` or $(command)
• String interpolation: "$VAR" or "${VAR}"
• Arrays: set -A ARRAY item1 item2 item3
• Arithmetic expansion: $((expression))
• Pattern matching: [[ string =~ pattern ]] (Korn shell style)
• Uses print command (Korn shell style) instead of echo

Fragment Authoring

Write valid mksh shell commands. Your fragment becomes the script body. The fragment code will execute as part of the shell script.

Fragments are injected at the point where print "Hello World!" appears, so you can replace the print statement or add additional commands.

Available Commands

Standard Unix utilities and mksh built-ins are available:

• print - Print text (Korn shell style)
• echo - Print text (POSIX style, also available)
• printf - Formatted output
• test / [ / [[ - Conditional tests
• if, while, for, until - Control structures
• grep, sed, awk - Text processing
• Standard Unix utilities

Common Patterns

• Output: print "message" or echo "message" or printf "%s\n" "message"
• Variables: NAME="value" and print "$NAME"
• Arrays: set -A ARRAY item1 item2 item3 and print "${ARRAY[@]}"
• Conditionals: if [[ condition ]]; then ... fi
• Loops: for i in 1 2 3 4 5; do print "$i"; done or for i in $(seq 1 5); do print "$i"; done
• Command substitution: RESULT=$(command)
• Arithmetic: $((A + B)) or let "result = A + B"
• Functions: function_name() { ... }
• Here documents: cat <<EOF ... EOF

Examples

# Simple output
print "Hello from fragment!"

# Variables
NAME="Alice"
print "Hello, $NAME!"

# Arithmetic
A=5
B=10
SUM=$((A + B))
print "Sum: $SUM"

# Arrays
set -A FRUITS apple banana cherry
for fruit in "${FRUITS[@]}"; do
    print "Fruit: $fruit"
done

# Conditionals
if [[ "test" == "test" ]]; then
    print "Testing mode"
else
    print "Normal mode"
fi

# Functions
greet() {
    local name="$1"
    print "Hello, $name!"
}

greet "World"

# Command substitution
DATE=$(date)
print "Current date: $DATE"

# Arithmetic loops (using seq)
for i in $(seq 1 5); do
    print "Count: $i"
done

# Multiple statements
print "First line"
print "Second line"
print "Third line"

# Nested conditionals
if [[ -n "$1" ]]; then
    if [[ "$1" == "hello" ]]; then
        print "Greeting received"
    else
        print "Other argument: $1"
    fi
else
    print "No argument provided"
fi

Caveats

• Variable assignment: no spaces around =
• Use [[ for Korn shell-specific tests, [ for POSIX compatibility
• Quote variables to prevent word splitting: "$VAR"
• Arrays use set -A syntax: set -A ARRAY item1 item2 item3
• Array access: "${ARRAY[@]}" for all elements, "${ARRAY[0]}" for first element
• Case-sensitive variable names
• Arithmetic expansion: $((expression)) (no $ inside)
• Function definitions: function_name() { ... } or function function_name { ... }
• Use local keyword inside functions to avoid global variable pollution
• Prefer print over echo for Korn shell style (though echo also works)
• Brace expansion like {1..5} does NOT work in mksh (use explicit lists or seq)

Fraglet Scripts

Echo Args

#!/usr/bin/env -S fragletc --vein=mksh
echo "Args: $*"

Mksh Fortune

#!/usr/bin/env -S fragletc --vein=mksh
# One from the vault: mksh fortunes
print "mksh: the shell that proves you can be small, fast, and POSIX at the same time."

Stdin Upper

#!/usr/bin/env -S fragletc --vein=mksh
while read -r line; do echo "$line" | tr "a-z" "A-Z"; done

Test

#!/usr/bin/env -S fragletc --vein=mksh

print "Hello World!"

Connections

Container Info