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@c \version "2.12.0"


@node Running lilypond
@chapter Running @command{lilypond}

This chapter details the technicalities of running LilyPond.

@menu
* Normal usage::
* Command-line usage::
* Error messages::
@end menu


@node Normal usage
@section Normal usage

Most users run LilyPond through a GUI; see 
FIXME FIXME FIXME
@c @rlearning{First steps} if
you have not read this already.


@node Command-line usage
@section Command-line usage

This section contains extra information about using LilyPond on the
command-line.  This may be desirable to pass extra options to the
program.  In addition, there are certain extra @q{helper} programs (such
as @code{midi2ly}) which are only available on the command-line.

By @q{command-line}, we mean the command line in the operating system.
Windows users might be more familiar with the terms @q{DOS shell} or
@q{command shell}; MacOS@tie{}X users might be more familiar with the terms
@q{terminal} or @q{console}.  They should also consult 
FIXME 
@c @ref{Setup for MacOS X}.

Describing how to use this part of an operating system is outside the
scope of this manual; please consult other documentation on this topic
if you are unfamiliar with the command-line.

@menu
* Invoking lilypond::
* Command line options for lilypond::
* Environment variables::
@end menu

@node Invoking lilypond
@subsection Invoking @command{lilypond}

@cindex Invoking @command{lilypond}
@cindex command line options for @command{lilypond}
@cindex options, command line
@cindex switches


The @command{lilypond} executable may be called as follows from the command line.

@example
lilypond [@var{option}]@dots{} @var{file}@dots{}
@end example


When invoked with a filename that has no extension, the @file{.ly}
extension is tried first.  To read input from stdin, use a
dash (@code{-}) for @var{file}.

When @file{filename.ly} is processed it will produce @file{filename.ps}
and @file{filename.pdf} as output.  Several files can be specified;
they will each be processed independently.  @footnote{The status of
GUILE is not reset after processing a @code{.ly} file, so be careful
not to change any system defaults from within Scheme.}

If @file{filename.ly} contains more than one @code{\score}
block, then the rest of the scores will be output in numbered files,
starting with @file{filename-1.pdf}.  In addition, the value of
@code{output-suffix} will be inserted between the basename and the
number.  An input file containing

@example
#(define output-suffix "violin")
\score @{ @dots{} @}
#(define output-suffix "cello")
\score @{ @dots{} @}
@end example

@noindent
will output @var{base}@file{-violin.pdf} and
@var{base}@file{-cello-1.pdf}.


@node Command line options for lilypond
@subsection Command line options for @command{lilypond}

The following options are supported:

@table @code

@item -e,--evaluate=@var{expr}
Evaluate the Scheme @var{expr} before parsing any @file{.ly} files.
Multiple @code{-e} options may be given, they will be evaluated
sequentially.

The expression will be evaluated in the @code{guile-user} module, so
if you want to use definitions in @var{expr}, use

@example
lilypond -e '(define-public a 42)'
@end example

@noindent
on the command-line, and include

@example
#(use-modules (guile-user))
@end example

@noindent
at the top of the @code{.ly} file.

@item -f,--format=@var{format}
which formats should be written.  Choices for @code{format} are
@code{svg}, @code{ps}, @code{pdf}, and @code{png}.

Example: @code{lilypond -fpng @var{filename}.ly}



@item -d,--define-default=@var{var}=@var{val}
This sets the internal program option @var{var} to the Scheme value
@var{val}.  If @var{val} is not supplied, then @var{#t} is used.  To
switch off an option, @code{no-} may be prefixed to @var{var}, e.g.

@cindex point and click, command line

@example
-dno-point-and-click
@end example

@noindent
is the same as
@example
-dpoint-and-click='#f'
@end example

Here are a few interesting options.

@table @samp
@item help
Running @code{lilypond -dhelp} will print all of the @code{-d} options
available.

@item paper-size
This option sets the default paper-size,
@example
-dpaper-size=\"letter\"
@end example

@noindent
Note that the string must be enclosed in escaped quotes ( @code{\"} ).
@c Match " in previous line to help context-sensitive editors

@item safe
Do not trust the @code{.ly} input.

When LilyPond formatting is available through a web server, either the
@code{--safe} or the @code{--jail} option @b{MUST} be passed.  The
@code{--safe} option will prevent inline Scheme code from wreaking
havoc, for example

@quotation
@verbatim
#(system "rm -rf /")
{
  c4^#(ly:export (ly:gulp-file "/etc/passwd"))
}
@end verbatim
@end quotation

The @code{-dsafe} option works by evaluating in-line Scheme
expressions in a special safe module.  This safe module is derived from
GUILE @file{safe-r5rs} module, but adds a number of functions of the
LilyPond API.  These functions are listed in @file{scm/@/safe@/-lily@/.scm}.

In addition, safe mode disallows @code{\include} directives and
disables the use of backslashes in @TeX{} strings.

In safe mode, it is not possible to import LilyPond variables
into Scheme.

@code{-dsafe} does @emph{not} detect resource overuse.  It is still possible to
make the program hang indefinitely, for example by feeding cyclic data
structures into the backend.  Therefore, if using LilyPond on a
publicly accessible webserver, the process should be limited in both
CPU and memory usage.

The safe mode will prevent many useful LilyPond snippets from being
compiled.  The @code{--jail} is a more secure alternative, but
requires more work to set up.

@cindex output format, setting
@item backend
the output format to use for the back-end.  Choices for @code{format} are
@table @code
@item ps
@cindex PostScript output
 for PostScript.

  Postscript files include TTF, Type1 and OTF fonts.  No subsetting of
  these fonts is done.  When using oriental character sets, this can
  lead to huge files.

@item eps
 for encapsulated PostScript.  This dumps every page (system) as a separate
@file{EPS} file, without fonts, and as one collated @file{EPS} file with
all pages (systems) including fonts.

This mode is used by default by @command{lilypond-book}.

@item svg
@cindex SVG (Scalable Vector Graphics)
 for SVG (Scalable Vector Graphics).

 This creates a single SVG file containing the entire music output
 with no embedded fonts.  It is recommended to install the Century
 Schoolbook fonts, included with your LilyPond installation, for
 optimal rendering.  Under UNIX, simply copy these fonts from the
 LilyPond directory (typically
 @file{/usr/share/lilypond/VERSION/fonts/otf/}) to
 @file{~/.fonts/}.  The SVG output should be compatible with any
 SVG editor or user agent.

@item scm
@cindex Scheme dump
 for a dump of the raw, internal Scheme-based drawing commands.

@item null
 do not output a printed score; has the same effect as @code{-dno-print-pages}.
@end table

Example: @code{lilypond -dbackend=svg @var{filename}.ly}

@item preview
Generate an output file containing the titles and the first system

@item print-pages
Generate the full pages, the default.  @code{-dno-print-pages} is
useful in combination with @code{-dpreview}.

@end table



@item -h,--help
Show a summary of usage.

@item -H,--header=@var{FIELD}
Dump a header field to file @file{BASENAME.@var{FIELD}}.

@item --include, -I=@var{directory}
Add @var{directory} to the search path for input files.
@cindex file searching
@cindex search path

@item -i,--init=@var{file}
Set init file to @var{file} (default: @file{init.ly}).

@item -o,--output=@var{FILE}
Set the default output file to @var{FILE}.  The appropriate
suffix will be added (e.g. @code{.pdf} for pdf)

@item --ps
Generate PostScript.

@item --png
Generate pictures of each page, in PNG format.  This implies
@code{--ps}.  The resolution in DPI of the image may be set with
@example
-dresolution=110
@end example

@item --pdf
Generate PDF.  This implies @code{--ps}.



@item -j,--jail=@var{user},@var{group},@var{jail},@var{dir}
Run @command{lilypond} in a chroot jail.

The @code{--jail} option provides a more flexible alternative to
@code{--safe} when LilyPond formatting is available through a web
server or whenever LilyPond executes externally provided
sources.

The @code{--jail} option works by changing the root of @command{lilypond} to
@var{jail} just before starting the actual compilation process.  The user
and group are then changed to match those provided, and the current
directory is changed to @var{dir}.  This setup guarantees that it is not
possible (at least in theory) to escape from the jail.  Note that for
@code{--jail} to work @command{lilypond} must be run as root, which is usually
accomplished in a safe way using @command{sudo}.

Setting up a jail is a slightly delicate matter, as we must be sure that
LilyPond is able to find whatever it needs to compile the source
@emph{inside the jail}.  A typical setup comprises the following items:

@table @asis
@item Setting up a separate filesystem
A separate filesystem should be created for LilyPond, so that it can be
mounted with safe options such as @code{noexec}, @code{nodev}, and
@code{nosuid}.  In this way, it is impossible to run executables or to
write directly to a device from LilyPond.  If you do not want to create a
separate partition, just create a file of reasonable size and use it to
mount a loop device.  A separate filesystem also guarantees that LilyPond
cannot write more space than it is allowed.

@item Setting up a separate user
A separate user and group (say, @code{lily}/@code{lily}) with low
privileges should be used to run LilyPond inside the jail.  There should
be a single directory writable by this user, which should be passed in
@var{dir}.

@item Preparing the jail
LilyPond needs to read a number of files while running.  All these files
are to be copied into the jail, under the same path they appear in the
real root filesystem.  The entire content of the LilyPond installation
(e.g., @file{/usr/share/lilypond})
should be copied.

If problems arise, the simplest way to trace them down is to run
LilyPond using @command{strace}, which will allow you to determine which
files are missing.

@item Running LilyPond
In a jail mounted with @code{noexec} it is impossible to execute any external
program.  Therefore LilyPond must be run with a backend that does not
require any such program.  As we already mentioned, it must be also run
with superuser privileges (which, of course, it will lose immediately),
possibly using @command{sudo}.  It is a good idea to limit the number of
seconds of CPU time LilyPond can use (e.g., using @command{ulimit
-t}), and, if your operating system supports it, the amount of memory
that can be allocated.
@end table


@item -v,--version
Show version information.

@item -V,--verbose
Be verbose: show full paths of all files read, and give timing
information.

@item -w,--warranty
Show the warranty with which GNU LilyPond comes. (It comes with
@strong{NO WARRANTY}!)
@end table

@node Environment variables
@subsection Environment variables


@cindex LANG
@cindex LILYPOND_DATADIR

@command{lilypond} recognizes the following environment variables:
@table @code
@item LILYPOND_DATADIR
This specifies a directory where locale messages and
data files will be looked up by default.  The directory should contain
subdirectories called @file{ly/}, @file{ps/}, @file{tex/}, etc.

@item LANG
This selects the language for the warning messages.

@item LILYPOND_GC_YIELD
With this variable the memory footprint and performance can be
adjusted.  It is a percentage tunes memory management behavior.  With
higher values, the program uses more memory, with smaller values, it
uses more CPU time.  The default value is @code{70}.

@end table


@node Error messages
@section Error messages

@cindex error messages
Different error messages can appear while compiling a file:

@table @emph

@item Warning
@cindex warning
Something looks suspect.  If you are requesting something out of the
ordinary then you will understand the message, and can ignore it.
However, warnings usually indicate that something is wrong with the
input file.

@item Error
Something is definitely wrong.  The current processing step (parsing,
interpreting, or formatting) will be finished, but the next step will
be skipped.

@item Fatal error
@cindex error
@cindex fatal error
Something is definitely wrong, and LilyPond cannot continue.  This
happens rarely.  The most usual cause is misinstalled fonts.

@item Scheme error
@cindex trace, Scheme
@cindex call trace
@cindex Scheme error
Errors that occur while executing Scheme code are caught by the Scheme
interpreter.  If running with the verbose option (@code{-V} or
@code{--verbose}) then a call trace of the offending
function call is printed.

@item Programming error
@cindex Programming error
There was some internal inconsistency.  These error messages are
intended to help the programmers and debuggers.  Usually, they can be
ignored.  Sometimes, they come in such big quantities that they obscure
other output.

@item Aborted (core dumped)
This signals a serious programming error that caused the program to
crash.  Such errors are considered critical.  If you stumble on one,
send a bug-report.
@end table

@cindex errors, message format
If warnings and errors can
be linked to some part of the input file, then error messages have the
following form

@example
@var{filename}:@var{lineno}:@var{columnno}: @var{message}
@var{offending input line}
@end example

A line-break is inserted in the offending line to indicate the column
where the error was found.  For example,

@example
test.ly:2:19: error: not a duration: 5
  @{ c'4 e'
           5 g' @}
@end example

These locations are LilyPond's best guess about where the warning or
error occurred, but (by their very nature) warnings and errors occur
when something unexpected happens.  If you can't see an error in the
indicated line of your input file, try checking one or two lines
above the indicated position.