MATLAB: Does adding a semicolon (;) at the end of SYSTEM command in MATLAB 7.6 (R2008a) does not suppress the output display

MATLABsemi-colon

I am trying to use SYSTEM function and I add a semicolon at the end of my MATLAB statement. I expect MATLAB to suppress any output generated from that statement, but it still displays the output.

Reproduction steps:

system('cd');

As I have added a semicolon at the end I expect nothing to be displayed on the command line after the system command is executed. But it still displays the path of current directory.

Best Answer

The ability to suppress the output of SYSTEM function is not available in MATLAB 7.6 (R2008a).

To work around this issue, store the outputs of SYSTEM command in some variable. For instance:

[status,result]=system('cd');

If the command runs successfully, 'status' is 0 and 'result' contains the output from command. If command fails or does not exist on your operating system, 'status' is a nonzero value and 'result' contains an explanatory message.

Related Solutions

MATLAB: Do SYSTEM commands (like LS) not function as expected when I call them from MATLAB 7.11 (R2010b)

This behavior is due to interactions between MATLAB system command and underlying Linux shell. In particular, some terminal settings could lead to additional characters being returned by the call to the Unix shell.

To work around this issue try the following within MATLAB:

Before issuing any commands on the MATLAB command prompt:

1) Set MATLAB_SHELL environment variable to /bin/sh:

>> setenv('MATLAB_SHELL','/bin/sh');

2) Test the command that is causing the error.

3) Modify your .bashrc/.cshrc files to set MATLAB_SHELL to /bin/sh

Note: it is possible for step 1 to not fix the issue on its own. If just setting MATLAB_SHELL within MATLAB does not resolve the issue:

1) Shut down MATLAB

2) Modify your .bashrc/.cshrc files to set MATLAB_SHELL to /bin/sh

3) Open a new Linux terminal

4) Start MATLAB

5) verify whether you get correct output

If neither approaches resolve the issue, and you are issuing custom Linux commands via the SYSTEM call or the ! operator try the following:

If your command takes the format:

>> [a, b] = system('foo')

replace it with

>> [a, b] = system('foo < /dev/null')

Using the < /dev/null redirect will disable interactive input from MATLAB and should remove character corruption from the output.

MATLAB: Are changes lost in MATLAB 7.0 (R14) when using the “!” (bang) operator or the SYSTEM function to change environmental variables

This information has been added to the documentation in Release 14 Service Pack 2 (R14SP2). For previous releases, please read below for any possible workarounds:

When you use the ! (bang) operator or SYSTEM, a new thread is created for the commands. So, in the new process, the environmental variables are changed. However, once the commands are completed, the process is ended. When you check afterwards, the environmental variables are unchanged because you are looking at the same thread as before.

In order to execute commands with specific environmental variables set, place all of the commands inside the call to SYSTEM. One helpful note, you can separate commands in DOS using an ampersand (&) and a semi-colon (;) on UNIX.

Alternatively, you can set the environmental variables before starting MATLAB.

Best Answer

Related Solutions

MATLAB: Do SYSTEM commands (like LS) not function as expected when I call them from MATLAB 7.11 (R2010b)

MATLAB: Are changes lost in MATLAB 7.0 (R14) when using the “!” (bang) operator or the SYSTEM function to change environmental variables

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