Command Reference


The most common commands and options are shown in section Invoking GHDL. Here the advanced and experimental features are described.

Environment variables


Misc commands

There are a few GHDL commands which are seldom useful.

Help [-h]

--help, -h

Display (on the standard output) a short description of the all the commands available. If the help switch is followed by a command switch, then options for this later command are displayed:

ghdl --help
ghdl -h
ghdl -h command

Display config [--disp-config]

--disp-config <[options]>

Display the program paths and options used by GHDL. This may be useful to track installation errors.

Display standard [--disp-standard]

--disp-standard <[options]>

Display the std.standard package.

Version [--version]

--version, -v

Display the GHDL version and exit.

File commands

The following commands act on one or several files. These are not analyzed, therefore, they work even if a file has semantic errors.

Pretty print [--pp-html]

--pp-html <[options] file...>

The files are just scanned and an html file, with syntax highlighting is generated on standard output. Since the files are not even parsed, erroneous files or incomplete designs can be pretty printed.

The style of the html file can be modified with the --format= option:

  • By default or when the --format=html2 option is specified, the output is an HTML 2.0 file, with colours set through <FONT> tags.
  • When the --format=css option is specified, the output is an HTML 4.0 file, with colours set through a CSS file, whose name is ghdl.css. See Cross-reference_command, for more details about this CSS file.

Find [-f]

-f <file...>

The files are scanned, parsed and the names of design units are displayed. Design units marked with two stars are candidate to be at the apex of a design hierarchy.

Chop [--chop]

--chop <files...>

The provided files are read, and a file is written in the current directory for every design unit. Each filename is build according to the type:

  • For an entity declaration, a package declaration or a configuration the file name is NAME.vhdl, where NAME is the name of the design unit.
  • For a package body, the filename is NAME-body.vhdl.
  • Finally, for an architecture ARCH of an entity ENTITY, the filename is ENTITY-ARCH.vhdl.

Since the input files are parsed, this command aborts in case of syntax error. The command aborts too if a file to be written already exists.

Comments between design units are stored into the most adequate files.

This command may be useful to split big files, if your computer has not enough memory to compile such files. The size of the executable is reduced too.

Lines [--lines]

--lines <files...>

Display on the standard output lines of files preceded by line number.

GCC/LLVM only commands

Bind [--bind]

--bind <[options] primary_unit [secondary_unit]>

Performs only the first stage of the elaboration command; the list of objects files is created but the executable is not built. This command should be used only when the main entry point is not GHDL.


--mb-comments, -C

Allow multi-bytes chars in a comment


Use synthesizer rules for component binding. During elaboration, if a component is not bound to an entity using VHDL LRM rules, try to find in any known library an entity whose name is the same as the component name.

This rule is known as synthesizer rule.

There are two key points: normal VHDL LRM rules are tried first and entities are searched only in known library. A known library is a library which has been named in your design.

This option is only useful during elaboration.


Use COMMAND as the command name for the compiler. If COMMAND is not a path, then it is searched in the path.


Use COMMAND as the command name for the assembler. If COMMAND is not a path, then it is searched in the path. The default is as.


Use COMMAND as the linker driver. If COMMAND is not a path, then it is searched in the path. The default is gcc.

Passing options to other programs


These options are only available with GCC/LLVM.

For many commands, GHDL acts as a driver: it invokes programs to perform the command. You can pass arbitrary options to these programs.

Both the compiler and the linker are in fact GCC programs. See the GCC manual for details on GCC options.


Pass OPTION as an option to the compiler.


Pass OPTION as an option to the assembler.


Pass OPTION as an option to the linker.