syntax.md

Linuxify Shell Interpreter Syntax Reference

Shebang Lines

#!default          # Use internal Linuxify interpreter
#!lish             # Use internal Linuxify interpreter (alias)
#!bash             # Use internal Linuxify interpreter (alias)
#!sh               # Use internal Linuxify interpreter (alias)
#!/path/to/interp  # Use external interpreter

---

Variables

# Assignment
NAME="value"
COUNT=42

# Usage
echo $NAME
echo ${NAME}
echo "Hello $NAME"

# Special variables
$?                 # Exit code of last command

---

Command Substitution

# Using $() - preferred
FILES=$(ls)
COUNT=$(wc -l < file.txt)
echo "Today is $(date)"

# Using backticks - legacy
FILES=`ls`
CURRENT=`pwd`

# In conditions
if [ -n "$(git status)" ]; then
    echo "Git status available"
fi

# Nested commands
echo "Files: $(echo $(ls) | wc -w)"

---

Comments

# This is a comment
echo "hello"  # Inline comment

---

Control Flow

If Statement

if [ condition ]; then
    commands
fi

if [ condition ]; then
    commands
else
    other_commands
fi

if [ condition ]; then
    commands
elif [ other_condition ]; then
    other_commands
else
    fallback_commands
fi

For Loop

for var in item1 item2 item3; do
    echo $var
done

for i in 1 2 3 4 5; do
    echo "Number: $i"
done

While Loop

while [ condition ]; do
    commands
done

Functions

# Define a function
greet() {
    echo "Hello, $1!"
    echo "All args: $@"
    echo "Arg count: $#"
}

# Alternative syntax
function say_hello {
    echo "Hi there, $1!"
}

# Call functions with arguments
greet "World"
greet "Alice" "Bob" "Charlie"

# Positional parameters:
# $0 - function name
# $1-$9 - arguments
# $# - number of arguments
# $@ - all arguments

Case Statement (Switch)

case $variable in
    pattern1)
        commands
        ;;
    pattern2 | pattern3)
        commands
        ;;
    prefix*)
        echo "Starts with prefix"
        ;;
    *suffix)
        echo "Ends with suffix"
        ;;
    *)
        echo "Default case"
        ;;
esac

# Example
check_os() {
    case $1 in
        windows | win)
            echo "Windows detected"
            ;;
        linux | ubuntu)
            echo "Linux detected"
            ;;
        *)
            echo "Unknown OS"
            ;;
    esac
}

---

Test Conditions [ ... ]

File Tests

Operator	Description
-f FILE	File exists
-d FILE	Directory exists
-e FILE	Path exists

String Tests

Operator	Description
-z STR	String is empty
-n STR	String is not empty
a = b	Strings are equal
a == b	Strings are equal
a != b	Strings are not equal

Numeric Tests

Operator	Description
a -eq b	Equal
a -ne b	Not equal
a -lt b	Less than
a -le b	Less than or equal
a -gt b	Greater than
a -ge b	Greater than or equal

---

Operators

Pipes

cmd1 | cmd2              # Pipe output of cmd1 to cmd2

Redirection

cmd > file               # Redirect stdout to file (overwrite)
cmd >> file              # Redirect stdout to file (append)
cmd < file               # Redirect stdin from file

Command Chaining

cmd1 && cmd2             # Run cmd2 only if cmd1 succeeds
cmd1 || cmd2             # Run cmd2 only if cmd1 fails
cmd1; cmd2               # Run commands sequentially
cmd &                    # Run command in background

---

Available Commands

Interpreter Built-ins

Command	Description
echo <args>	Print arguments to stdout
cd <dir>	Change current directory
pwd	Print working directory
export VAR=val	Set environment variable
set	Display all variables
exit [code]	Exit the shell
test <expr>	Evaluate conditional expression
[ expr ]	Same as test
true	Return exit code 0
false	Return exit code 1
help	Display help information

All Linuxify Commands (Fallback)

When running scripts with #!default, ALL Linuxify shell commands are available:

ls, cat, mkdir, rm, mv, cp, touch, chmod, chown, head, tail, grep, find,
wc, sort, uniq, diff, tar, Lino, whoami, hostname, date, uptime, df, ps,
kill, jobs, bg, fg, history, alias, unalias, source, man, clear, wget,
curl, ssh, scp, ping, netstat, ifconfig, setup, registry, sudo, ...

External Commands (Registry & PATH)

Any command registered in the Linuxify registry or available in PATH works:

git, python, node, npm, code, docker, kubectl, sql, gcc, make, ...

Example using external commands in a script:

#!default

git status
python --version
node -e "console.log('Hello from Node!')"

---

Quoting

"double quotes"          # Variables expanded, special chars preserved
'single quotes'          # Literal string, no expansion

---

Example Script

#!default

NAME="World"
COUNT=3

echo "Hello $NAME!"

for i in 1 2 3; do
    if [ $i -eq 2 ]; then
        echo "Found two!"
    else
        echo "Number: $i"
    fi
done

if [ -f "myfile.txt" ]; then
    echo "File exists"
else
    echo "File not found"
fi