MATLAB: Perplexing output from the system() command

bashMATLABshellsystem

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.)

Best Answer

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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