Conditionals

Use @if, @elif, @else, and @end to conditionally execute commands inside a recipe.

Basic If/Else

task install:
    @if env(CI)
        npm ci
    @else
        npm install
    @end

If/Elif/Else

task deploy:
    @if env(PRODUCTION)
        echo "Deploying to production"
    @elif env(STAGING)
        echo "Deploying to staging"
    @else
        echo "Deploying to development"
    @end

Condition Functions

Function	Description
env(VAR)	True if environment variable is set and non-empty
exists(path)	True if file or directory exists
command(name)	True if command exists in PATH
eq(a, b)	True if strings are equal
neq(a, b)	True if strings are not equal
is_watching()	True if running in watch mode (-w)
is_dry_run()	True if running in dry-run mode (-n)
is_verbose()	True if running in verbose mode (-v)
is_macos()	True if running on macOS
is_linux()	True if running on Linux
is_windows()	True if running on Windows
is_unix()	True if running on Unix-like OS (Linux, macOS, BSD)
is_platform(name)	True if running on the specified platform

How Arguments Are Resolved

eq(), neq(), and exists() all resolve their arguments before evaluating. The resolution order is:

1. $VAR or ${VAR} — looked up as an environment variable
2. {{var}} — looked up as a Jake variable (from your Jakefile)
3. Plain identifier — looked up as a Jake variable
4. Quoted string — used as a literal value

env_var    = "staging"        # Jake variable

task deploy:
    # $ENV resolves as environment variable
    @if eq($DEPLOY_ENV, production)
        echo "Deploying to prod"
    @end

    # Jake variable via plain identifier
    @if eq(env_var, staging)
        echo "Deploying to staging"
    @end

    # Jake variable via {{}} syntax
    @if eq({{env_var}}, staging)
        echo "Same thing"
    @end

    # Quoted literal — always the string "production"
    @if eq($DEPLOY_ENV, "production")
        echo "Explicit string comparison"
    @end

Unresolved variables (not found anywhere) silently become empty strings. A missing variable won’t error — the condition just evaluates against "".

Limitation: Positional Arguments

Positional arguments ($1, $2, {{$1}}) do not work inside condition expressions. Condition strings are evaluated before variable expansion, so {{$1}} in a condition is treated as a lookup for a variable literally named $1, which never exists.

Use named recipe parameters instead:

# Works
task deploy env="staging":
    @if eq(env, production)
        echo "Deploying to production!"
    @else
        echo "Deploying to {{env}}"
    @end

$ jake deploy env=production

String Comparison

Compare Jake variables, environment variables, or literals:

task build:
    @if eq($BUILD_MODE, release)
        cargo build --release
    @else
        cargo build
    @end

mode = "debug"

task compile:
    @if neq(mode, release)
        echo "Building in debug mode"
    @end

File Existence

exists() checks whether a file or directory exists on disk. Pass a path, a Jake variable, or a quoted string:

task setup:
    @if exists(node_modules)
        echo "Dependencies already installed"
    @else
        npm install
    @end

task build:
    @if exists(dist/index.html)
        echo "Already built, skipping"
    @else
        npm run build
    @end

Note: exists() only handles a single whole-path variable reference (exists({{dir}})) — it doesn’t expand variables inline within a path string like exists({{dir}}/file.txt).

Environment Variables

env(VAR) is true if the variable is set and non-empty:

task install:
    @if env(CI)
        npm ci
    @else
        npm install
    @end

task deploy:
    @if env(PRODUCTION)
        echo "Deploying to production"
    @elif env(STAGING)
        echo "Deploying to staging"
    @else
        echo "Deploying to development"
    @end

Command Availability

Check if tools are available before using them:

task build:
    @if command(docker)
        docker build -t myapp .
    @elif command(podman)
        podman build -t myapp .
    @else
        echo "No container runtime found"
    @end

task deploy:
    @if command(kubectl)
        kubectl apply -f k8s/
    @else
        echo "kubectl not installed — skipping deploy"
    @end

Works with absolute paths too:

task check:
    @if command(/usr/local/bin/custom-tool)
        /usr/local/bin/custom-tool run
    @end

Runtime State

Check how jake was invoked:

task build:
    @if is_watching()
        echo "Watch mode: skipping expensive lint"
    @else
        npm run lint
    @end
    npm run build

task deploy:
    @if is_dry_run()
        echo "[DRY RUN] Would deploy to production"
    @else
        rsync dist/ server:/var/www/
    @end

task test:
    @if is_verbose()
        npm test -- --verbose
    @else
        npm test
    @end

Platform Detection

task install:
    @if is_macos()
        brew install ripgrep
    @elif is_linux()
        apt-get install ripgrep
    @elif is_windows()
        choco install ripgrep
    @end

Use is_unix() for commands that work on all Unix-like systems (Linux, macOS, BSDs):

task permissions:
    @if is_unix()
        chmod +x ./script.sh
    @end

Use is_platform() to match any platform by OS tag name:

task build:
    @if is_platform(freebsd)
        gmake build
    @else
        make build
    @end

Error Behavior

If a condition expression is malformed or uses an unknown function, Jake treats it as false and skips the block — no error is produced. If you see a block silently not executing, double-check the condition syntax.

Nesting

@if blocks can be nested to arbitrary depth:

task deploy:
    @if env(CI)
        @if is_macos()
            echo "CI on macOS"
        @else
            echo "CI on Linux/Windows"
        @end
    @else
        echo "Local build"
    @end