Perplexing output from the system() command

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the cyclist
the cyclist 2017-1-19
评论： Jess Crawshaw 2020-4-28
I am running R2106b on a Macbook Pro OS X Yosemite.
In a Terminal window (using bash shell), if I type
which which
I get the expected output
/usr/bin/which
and similarly
which psql
yields
/usr/local/bin/psql
All is well and good so far. But if I issue these same command from within MATLAB, using the system() command, I get output that perplexes me. As expected, when I type
[status cmdout] = system('which which')
I get
status =
0
cmdout =
'/usr/bin/which
'
But from
[status cmdout] = system('which psql')
I get
status =
1
cmdout =
0×0 empty char array
Finally, if I point directly to the known directory (which in my real application I would not know) ...
[status cmdout] = system('which /usr/local/bin/psql')
then the command is found
status =
0
cmdout =
'/usr/local/bin/psql
'
Does anyone have some insight into what is happening here? I am not a Unix expert by any means. But the whole thing seems to be a bit of a shell game. ;-)
(I can add the why I am doing this if needed, but I won't burden folks just yet.)
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Walter Roberson
Walter Roberson 2017-6-23
The causes are described below: when you start MATLAB from the icon, that is not a login shell so your shell setup files are not run and so your PATH environment variable does not include everything you might be expecting.
Jess Crawshaw
Jess Crawshaw 2020-4-28
Your answer below completely fixed my problems, thanks for this

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采纳的回答

Walter Roberson
Walter Roberson 2017-1-25
psql is not on your PATH environment variable inside of MATLAB. When you enter the terminal then that would be a login shell and your bash profile would be executed, but when you start MATLAB from an icon then that is not a login shell and your bash profile would not be executed.
See http://stackoverflow.com/questions/22465332/setting-path-environmental-variables-in-osx-permanently
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the cyclist
the cyclist 2017-1-25
编辑：the cyclist 2017-1-25
Thanks.
For the sake of others who may read this ...
The specific solution for me was to add /usr/local/bin to my MATLAB PATH environment variable. I did this by adding the line
setenv('PATH', [getenv('PATH') ':/usr/local/bin'])
to my startup file.
Walter Roberson
Walter Roberson 2017-9-10
/etc/profile and ~/.bashrc and ~/.bash_profile and ~/.bash_login and ~/.profile are only executed for interactive shells.
/etc/bashrc (Red Hat) or /etc/bash.bashrc (Ubuntu) are executed for non-interactive shells.

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更多回答（1 个）

Nikunj Kothari
Nikunj Kothari 2017-1-25
Are you getting the same output if instead of using system(), you use the exclamation point? The following documentation link elaborates on how to properly run external commands and scripts:
http://www.mathworks.com/help/matlab/matlab_external/run-external-commands-scripts-and-programs.html

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