MATLAB_COMMANDLINE - Running MATLAB From a Unix Commandline
MATLAB_COMMANDLINE
Running MATLAB From a Unix Commandline
MATLAB_COMMANDLINE
is a directory of MATLAB programs which
illustrate how MATLAB can be used from the UNIX commandline,
rather than within the usual MATLAB command window.
There may be cases where this mode is more convenient (because
you know what you want MATLAB to do, and you don't want to interact)
or necessary (because you're logging into a remote system, and can't
get X-Windows set up properly to transmit a command window).
Some issues that immediately arise include:
Where is MATLAB?
(how should the program be invoked?)
Where will MATLAB's input come from?
(how do we tell it what to do?)
Where does MATLAB's output go?
(where does the printed output go?)
How does MATLAB know to stop?
Where is MATLAB's visual interface?
(how do we suppress the graphical interface?)
Where is MATLAB's default directory?
(if files are read or written, where will that occur?)
Where does MATLAB's graphical output go?
(what options allow us to create and save graphical information?)
Licensing:
The computer code and data files described and made available on this web page
are distributed under
Related Data and Programs:
FORTRAN90 programs which
issue calls to MATLAB to carry out an auxillary calculation.
MATLAB programs which
contains some examples of scripts and M-files.
MATLAB and C programs which
illustrate how MATLAB can call a C function,
using the MEX facility.
MATLAB programs which
illustrate the use of the Matlab compiler, which allows you
to run a Matlab application outside the Matlab environment.
MATLAB programs which
illustrate how MATLAB can be run in batch mode using the CONDOR
queueing system.
MATLAB and FORTRAN77 programs which
illustrate how MATLAB can call a FORTAN77 function,
using the MEX facility.
examples of making movies using MATLAB;
examples of how the system command can be used to allow MATLAB
to issue commands to the computer operating system (UNIX or DOS);
examples which
illustrate the use of the MOAB job scheduler for a computer cluster.
Reference:
Duane Hanselman, Bruce Littlefield,
Mastering MATLAB 7,
Pearson Prentice Hall, 2005,
ISBN: 0-13-,
LC: QA297.H2963.
The Mathworks,
Using MATLAB, Version 6,
The Mathworks, 2002.
Where is MATLAB?
In order to run MATLAB, you probably simply type
However, this only happens because matlab is in your path,
that is, the executable program is in one of the directories that
the your login shell told the operating system to search.
When you want to run MATLAB in batch mode, you may need to specify
exactly where the MATLAB executable can be found.
(This might not
be necessary if you've set up your path carefully, but it's good to
know in any case.)
To identify exactly where the executable is,
which matlab
The response should be something like:
/usr/local/bin/matlab
This is the "full path name" of MATLAB on your machine.
start up MATLAB with this specification, the operating system will
never return a complaint like "command not found".
Where is MATLAB's Input?
MATLAB expects the user to issue a series of commands.
users are familiar with the idea of MATLAB "script" files, which
are simply text files containing a series of commands to MATLAB
that could have been entered interactively.
A script file typically
has a ".m" filename extension, such as "power_table.m".
The file power_table.m might consist simply of a computation of a table
of squares and cubes, as follows:
fprintf ( 1, '\n' );
fprintf ( 1, '
N-cubed\n' );
fprintf ( 1, '\n' );
for i = 1 : 10
fprintf ( 1, '
%10d\n', i, i^2, i^3 );
During an interactive
session with MATLAB, the commands in the script are executed simply
by invoking the script file's name:
&& power_table
You might suspect that part of the technique for running MATLAB
in batch mode will be to redirect MATLAB's input stream to
the M-file we have created, as in
/usr/local/bin/matlab < power_table.m
This is indeed part of the solution.
Note, however, that when we ran the M-file interactively, that even after
MATLAB carried out all the input commands in power_table.m, it still
expected more input.
If we're not careful, MATLAB will simply
continue to run, expecting more input from us.
The key to using MATLAB in batch mode is this idea of an
Presumably, though, the actual computation we want to
carry out is more complicated than this simple example.
prepare an appropriate M-file that completely defines this
calculation, that is, that instructs MATLAB on all the tasks
we need it to do, including where to find other input files,
what to name the output files, and so on, all without any chance
of interactive correction by us.
As you can imagine, this can
take some thought and patience.
This means that we will need to know precisely some things we often
don't worry about, such as what our default directory will be,
how we can create graphics, and how we can terminate the session
with MATLAB.
Where does MATLAB's output go?
If you simply issue the command
/usr/local/bin/matlab < power_table.m
then MATLAB starts up OK, and it knows where to get its output.
Of course there's output from these commands, and it has to go
somewhere.
In fact, it goes straight to
standard output - in this case, to the user terminal.
if you issue this command, you should see the table
of powers printed out.
That's fine for a test, but probably not
what you want for your big batch computation!
Of course we know what to do - simply redirect the standard output
(MATLAB's responses, that is) to a file:
/usr/local/bin/matlab
power_table_output.txt
This seems logical enough, but if you issue this command, you'll
probably note that the program never seems to terminate.
have to type CONTROL-C to kill it, and you may not actually have
any output in the output file.
That's because MATLAB, after reading
all the input in power_table.m, doesn't terminate, it just
waits patiently for you, just as it would in interactive mode.
We need to tell MATLAB when it's time to die!
How Does MATLAB Know to Stop?
When you want to end an interactive MATLAB session, you probably
go up to a pull-down menu and select QUIT.
However, we'll
have no access to menus in a batch job.
Instead, to get MATLAB to
terminate the session, we need to use the exit command.
So if we add an exit statement as the last line of our
power_table.m script, we can run it as follows:
/usr/local/bin/matlab
power_table_output.txt
It should be the case that this program begins, runs, and terminates,
all in an orderly fashion.
The output file includes our desired
results (plus some other junk).
The MathWorks, Inc.
Version 7.3.0.298 (R2006b)
August 03, 2006
To get started, type one of these: helpwin, helpdesk, or demo.
For product information, visit .
>> >> >> >> >> >> >> >> >> >> >>
However, you probably also noticed, after you issued the command,
that a MATLAB X-Window showed up, with the MATLAB logo.
because MATLAB doesn't quite realize that we're only interested in
a batch session.
It's establishing an X-Window connection to the
current display.
For now, this is a minor annoyance, but we'll
actually want to suppress this behavior entirely.
Where is MATLAB's visual interface?
On a UNIX system, MATLAB uses the X-Windows Interface to interact
with the user.
In a batch execution, this communication is not
necessary.
We don't need the initial "splash" which displays the MATLAB logo.
We can turn this off with the -nosplash option.
We also don't want the interactive menu window to be
set up, which can be suppressed with the -nodisplay option
Two other options are available which may be useful in suppressing
visual output and logs, the -nojvm option ("no Java Virtual
Machine") and -nodesktop.
Now our statement to run a batch job might look like this:
/usr/local/bin/matlab -nosplash -nodisplay -nojvm -nodesktop
power_table_output.txt
Of course, you can experiment to see which options are necessary.
I seem to be able to use the simpler commands:
matlab -nosplash
power_table_output.txt
Where is MATLAB's default directory?
When you use MATLAB as a simple calculator, you may not care
that MATLAB defines a working directory, which is the default location
where files will be created, and where certain things like user
M-files will be looked for.
If you have used M-files, you know that the easiest way to access them
is to "move" MATLAB's current working directory to the directory
containing your M- of course, you could also modify MATLAB's
"path", or even write out the full directory information needed to
find the file you are referring to.
When using MATLAB in batch, however, you'll probably need to know
where MATLAB sets its default working directory.
how to change the default working directory.
how to change the working directory at any time.
To find out where MATLAB sets its default working directory,
simply start the program up in interactive mode, and issue the
command pwd.
This directory is the same place that your
MATLAB batch jobs will start out in.
To change the default working directory (once and for all),
you need to create a file called startup.m with the
appropriate command, and place this file somewhere in the
MATLAB path (which you may or may not be able to do!).
The appropriate command to put in startup.m is
simply a cd command that moves to the directory
where you want to work.
cd /Users/burkardt/public_html/m_src/matlab_batch
that it is placed somewhere in the MATLAB path.
If the startup.m file cannot be used to reset the
default initial working directory, you just have to insert
a similar cd command in the main M-file that you want to
execute in batch.
When you explicitly move MATLAB's working
directory, you gain the ability to easily access all the M-files in
that directory, and to know how to access files you wish to
read or write.
Where does MATLAB's graphical output go?
Despite the fact that we've suppressed the visual interface interface
to MATLAB, we can still generate graphics...we won't see them of course,
unless we are careful to save them to files.
Perhaps the simplest example of a MATLAB graphics command is the
basic plot(x,y) command that makes a line plot of data.
So now let us suppose that our M-file generates some data,
as before, but rather than printing it, or writing it to a text
file, we wish to create a graphics file using the plot command.
One way to do this is simply to follow the plot command by
a version of the print command that "prints" the image
to a graphics file:
print -dpng 'power_plot.png';
Here the -dpng switch specifies that we wish to create
a PNG graphics file, and the second argument is simply the name
of the file to be created.
The graphics file created will be
stored in the current working directory.
Examples and Tests:
POWER_TABLE is an example in which we simply want to print a
table of powers of integers.
is a MATLAB M file which carries out the commands, and is
terminated by an exit command, so it is appropriate for
batch use.
is the output file from the simple batch invocation:
/usr/local/bin/matlab -nosplash -nodisplay
power_table_output.txt
POWER_WRITE is similar to POWER_TABLE except that the
table of integer powers is written to a file.
is a MATLAB M file which writes a table to a file.
is the file created by the program.
is the output file from the simple batch invocation:
/usr/local/bin/matlab -nosplash -nodisplay
power_write_output.txt
POWER_PLOT is similar to POWER_TABLE except that the
data is (X,Y) data, with X evenly spaced and Y randomized, and we
wish to plot the data, and export it as a PNG graphics file.
is a MATLAB M file which creates the data, plots it and exports it.
is the PNG graphics file created by the program.
is the output file from the simple batch invocation:
/usr/local/bin/matlab -nosplash -nodisplay
power_plot_output.txt
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Last revised on 24 April 2009.