NAME

crystal - compiler for the Crystal language

SYNOPSIS

crystal command [switches] programfile — [arguments]

DESCRIPTION

Crystal is a statically type-checked programming language. It was created with the beauty of Ruby and the performance of C in mind.

USAGE

You can compile and run a program by invoking the compiler with a single filename:

crystal some_program.cr

Crystal files usually end with the .cr extension, though this is not mandatory.

Alternatively you can use the run command:

crystal run some_program.cr

To create an executable use the build command:

crystal build some_program.cr

This will create an executable named "some_program".

Note that by default the generated executables are not fully optimized. To turn optimizations on, use the --release flag:

crystal build --release some_program.cr

Make sure to always use --release for production-ready executables and when performing benchmarks.

The optimizations are not turned on by default because the compile times are much faster without them and the performance of the program is still pretty good without them, so it allows to use the crystal command almost to be used as if it was an interpreter.

OPTIONS

The crystal command accepts the following options

init

init TYPE [DIR | NAME DIR]

Generates a new Crystal project.

TYPE is one of:

lib Creates a library skeleton
app Creates an application skeleton

This initializes the lib/app project folder as a git repository, with a license file, a README file, a shard.yml for use with shards (the Crystal dependency manager), a .gitignore file, and src and spec folders.

DIR - directory where project will be generated

NAME - name of project to be generated (default: basename of DIR)

Options:

-f, --force

Force overwrite existing files.

-s, --skip-existing

Skip existing files.

build

build [options] [programfile] [--] [arguments]

Compile program.

Options:

--cross-compile

Generate an object file for cross compilation and prints the command to build the executable. The object file should be copied to the target system and the printed command should be executed there. This flag mainly exists for porting the compiler to new platforms, where possible run the compiler on the target platform directly.

-d, --debug

Generate the output with symbolic debug symbols. These are read when debugging the built program with tools like lldb, gdb, valgrind etc. and provide mappings to the original source code for those tools.

--no-debug

Generate the output without any symbolic debug symbols.

-D FLAG, --define FLAG

Define a compile-time flag. This is useful to conditionally define types, methods, or commands based on flags available at compile time. The default flags are from the target triple given with --target-triple or the hosts default, if none is given.

--emit [asm|llvm-bc|llvm-ir|obj]

Comma separated list of types of output for the compiler to emit. You can use this to see the generated LLVM IR, LLVM bitcode, assembly, and object files.

--frame-pointers [auto|always|non-leaf]

Control the preservation of frame pointers. The default value, --frame-pointers=auto, will preserve frame pointers on debug builds and try to omit them on release builds (certain platforms require them to stay enabled). --frame-pointers=always will always preserve them, and non-leaf will only force their preservation on non-leaf functions.

-f text|json, --format text|json

Format of output. Defaults to text. The json format can be used to get a more parser-friendly output.

--error-trace

Show full error trace.

--ll

Dump LLVM assembly file to output directory.

--link-flags FLAGS

Pass additional flags to the linker. Though you can specify those flags on the source code, this is useful for passing environment specific information directly to the linker, like non-standard library paths or names. For more information on specifying linker flags on source, you can read the "C bindings" section of the documentation available on the official web site.

--mcpu CPU

Specify a specific CPU to generate code for. This will pass a -mcpu flag to LLVM, and is only intended to be used for cross- compilation. For a list of available CPUs, pass --mcpu help when building any Crystal source code. Passing --mcpu native will pass the host CPU name to tune performance for the host.

--mattr CPU

Override or control specific attributes of the target, such as whether SIMD operations are enabled or not. The default set of attributes is set by the current CPU. This will pass a -mattr flag to LLVM, and is only intended to be used for cross-compilation. For a list of available attributes, invoke "llvm-as < /dev/null | llc -march=xyz -mattr=help".

Specifies a specific code model to generate code for. This will pass a --code-model flag to LLVM.

--no-color

Disable colored output.

--no-codegen

Don’t do code generation, just parse the file.

-o

Specify filename of output.

--prelude

Specify prelude to use. The default one initializes the garbage collector. You can also use --prelude=empty to use no preludes. This can be useful for checking code generation for a specific source code file.

-O LEVEL

Optimization mode: 0 (default), 1, 2, 3. See OPTIMIZATIONS for details.

--release

Compile in release mode. Equivalent to -O3 --single-module

--error-trace

Show full stack trace. Disabled by default, as the full trace usually makes error messages less readable and not always deliver relevant information.

-s, --stats

Print statistics about the different compiler stages for the current build. Output time and used memory for each compiler process.

-p, --progress

Print statistics about the progress for the current build.

-t, --time

Print statistics about the execution time.

--single-module

Generate a single LLVM module. By default, one LLVM module is created for each type in a program. --release implies this option.

--threads NUM

Maximum number of threads to use for code generation. The default is 8 threads.

--target TRIPLE

Enable target triple; intended to use for cross-compilation. See llvm documentation for more information about target triple.

--verbose

Display the commands executed by the system.

--static

Create a statically linked executable.

--stdin-filename FILENAME

Source file name to be read from STDIN.

docs

Generate documentation from comments using a subset of markdown. The output is saved in html format on the created docs/ folder. More information about documentation conventions can be found at <https://crystal-lang.org/docs/conventions/documenting_code.html>.

Options:

--project-name NAME

Set the project name. The default value is extracted from shard.yml if available.

In case no default can be found, this option is mandatory.

--project-version VERSION

Set the project version. The default value is extracted from current git commit or shard.yml if available.

In case no default can be found, this option is mandatory.

--json-config-url URL

Set the URL pointing to a config file (used for discovering versions).

--source-refname REFNAME

Set source refname (e.g. git tag, commit hash). The default value is extracted from current git commit if available.

If this option is missing and can’t be automatically determined, the generator can’t produce source code links.

--source-url-pattern URL

Set URL pattern for source code links. The default value is extracted from git remotes ("origin" or first one) if available and the provider’s URL pattern is recognized.

Supported replacement tags:

%{refname}

commit reference

%{path}

path to source file inside the repository

%{filename}

basename of the source file

%{line}

line number

If this option is missing and can’t be automatically determined, the generator can’t produce source code links.

-o DIR, --output DIR

Set the output directory (default: ./docs).

-b URL, --canonical-base-url URL

Indicate the preferred URL with rel="canonical" link element.

-b URL, --sitemap-base-url URL

Set the sitemap base URL. Sitemap will only be generated when this option is set.

--sitemap-priority PRIO

Set the priority assigned to sitemap entries (default: 1.0).

--sitemap-changefreq FREQ

Set the changefreq assigned to sitemap entries (default: never).

env

env [variables]

Print Crystal-specific environment variables in a format compatible with shell scripts. If one or more variable names are given as arguments, it prints only the value of each named variable on its own line.

Variables:

CRYSTAL_CACHE_DIR

Please see ENVIRONMENT VARIABLES.

CRYSTAL_EXEC_PATH

Please see ENVIRONMENT VARIABLES.

CRYSTAL_LIBRARY_PATH

Please see ENVIRONMENT VARIABLES.

CRYSTAL_PATH

Please see ENVIRONMENT VARIABLES.

CRYSTAL_VERSION

Contains Crystal version.

eval

eval [options] [source]

Evaluate code from arguments or, if no arguments are passed, from the standard input. Useful for experiments.

Options:

-d, --debug

--no-debug

Generate the output without any symbolic debug symbols.

-D FLAG, --define FLAG

Define a compile-time flag. This is useful to conditionally define types, methods, or commands based on flags available at compile time. The default flags are from the target triple given with --target-triple or the hosts default, if none is given.

--error-trace

Show full error trace.

-O LEVEL

Optimization mode: 0 (default), 1, 2, 3. See OPTIMIZATIONS for details.

--release

Compile in release mode. Equivalent to -O3 --single-module

-s, --stats

Print statistics about the different compiler stages for the current build. Output time and used memory for each compiler process.

-p, --progress

Print statistics about the progress for the current build.

-t, --time

Print statistics about the execution time.

--no-color

Disable colored output.

play

play [options] [file]

Starts the crystal playground server on port 8080, by default.

Options:

-p PORT, --port PORT

Run the playground on the specified port. Default is 8080.

-b HOST, --binding HOST

Bind the playground to the specified IP.

-v, --verbose

Display detailed information of the executed code.

run

run [options] [programfile] [--] [arguments]

The default command. Compile and run program.

Options: Same as the build options.

spec

spec [options] [files]

Compile and run specs (in spec directory).

Options:

-d, --debug

--no-debug

Generate the output without any symbolic debug symbols.

-D FLAG, --define FLAG

--error-trace

Show full error trace.

-O LEVEL

Optimization mode: 0 (default), 1, 2, 3. See OPTIMIZATIONS for details.

--release

Compile in release mode. Equivalent to -O3 --single-module

-s, --stats

Print statistics about the different compiler stages for the current build. Output time and used memory for each compiler process.

-p, --progress

Print statistics about the progress for the current build.

-t, --time

Print statistics about the execution time.

--no-color

Disable colored output.

tool

tool [tool] [switches] [programfile] [--] [arguments]

Run a tool. The available tools are: context, dependencies, expand, flags, format, hierarchy, implementations, types, and unreachable.

Tools:

context

Show context for given location.

dependencies

Show tree of required source files.

Options:

-D FLAG, --define=FLAG

Define a compile-time flag. This is useful to con ditionally define types, methods, or commands based on flags available at compile time. The default flags are from the target triple given with --tar get-triple or the hosts default, if none is given.

-f FORMAT, --format=FORMAT

Output format 'tree' (default), 'flat', 'dot', or 'mermaid'.

-i PATH, --include=PATH

Include path in output.

-e PATH, --exclude=PATH

Exclude path in output.

--error-trace

Show full error trace.

--prelude

Specify prelude to use. The default one initializes the garbage collector. You can also use --pre lude=empty to use no preludes. This can be useful for checking code generation for a specific source code file.

--verbose

Show skipped and heads of filtered paths

expand

Show macro expansion for given location.

flags

Print all macro 'flag?' values

format

Format project, directories and/or files with the coding style used in the standard library. You can use the --checkflag to check whether the formatter would make any changes.

hierarchy

Show hierarchy of types from file. Also show class and struct members, with type and size. Types can be filtered with a regex by using the -e flag.

implementations

Show implementations for a given call. Use --cursor to specify the cursor position. The format for the cursor position is file:line:column.

types

Show type of main variables of file.

unreachable

Show methods that are never called. The text output is a list of lines with columns separated by tab.

Output fields:

count

sum of all calls to this method (only with --tallies option; otherwise skipped)

location

pathname, line and column, all separated by colon name

lines

length of the def in lines annotations

Options:

-D FLAG, --define=FLAG

Define a compile-time flag. This is useful to con ditionally define types, methods, or commands based on flags available at compile time. The default flags are from the target triple given with --target-triple or the hosts default, if none is given.

-f FORMAT, --format=FORMAT

Output format 'text' (default), 'json', 'codecov', or 'csv'.

--tallies

Print reachable methods and their call counts as well.

--check

Exit with error if there is any unreachable code.

-i PATH, --include=PATH

Include path in output.

-e PATH, --exclude=PATH

Exclude path in output (default: lib).

--error-trace

Show full error trace.

--prelude

Specify prelude to use. The default one initializes the garbage collector. You can also use --prelude=empty to use no preludes. This can be useful for checking code generation for a specific source code file.

clear_cache

Clear the compiler cache (located at 'CRYSTAL_CACHE_DIR').

help

Show help. Option --help or -h can also be added to each command for command-specific help.

version

Show version.

OPTIMIZATIONS

The optimization level specifies the codegen effort for producing optimal code. It’s a trade-off between compilation performance (decreasing per optimization level) and runtime performance (increasing per optimization level).

Production builds should usually have the highest optimization level. Best results are achieved with --release which also implies --single-module

-O0

No optimization (default)

-O1

Low optimization

-O2

Middle optimization

-O3

High optimization

-Os

Middle optimization with focus on file size

-Oz

Middle optimization aggressively focused on file size

ENVIRONMENT VARIABLES

CRYSTAL_CACHE_DIR

Defines path where Crystal caches partial compilation results for faster subsequent builds. This path is also used to temporarily store executables when Crystal programs are run with 'crystal run' rather than 'crystal build'.

CRYSTAL_EXEC_PATH

Determines the path where crystal looks for external sub-commands.

CRYSTAL_LIBRARY_PATH

Defines paths where Crystal searches for (binary) libraries. Multiple paths can be separated by ":". These paths are passed to the linker as -L flags.

The pattern '$ORIGIN' at the start of the path expands to the directory where the compiler binary is located. For example, '$ORIGIN/../lib/crystal' resolves the standard library path relative to the compiler location in a generic way, independent of the absolute paths (assuming the relative location is correct).

CRYSTAL_PATH

Defines paths where Crystal searches for required source files. Multiple paths can be separated by ":".

The pattern '$ORIGIN' at the start of the path expands to the directory where the compiler binary is located. For example, '$ORIGIN/../share/crystal/src' resolves the standard library path relative to the compiler location in a generic way, independent of the absolute paths (assuming the relative location is correct).

CRYSTAL_OPTS

Defines options for the Crystal compiler to be used besides the command line arguments. The syntax is identical to the command line arguments. This is handy when using Crystal in build setups, for example 'CRYSTAL_OPTS=--debug make build'.