shell command executed with "unix" fails in 2021a but works in 2017a

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John 2021-8-31

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https://ww2.mathworks.cn/matlabcentral/answers/1444189-shell-command-executed-with-unix-fails-in-2021a-but-works-in-2017a

评论： John 2021-9-1

To download weather forcast files in grib format from NOAA I build a query like this:

unixstr = '/usr/bin/curl -k https://nomads.ncep.noaa.gov/pub/data/nccf/com/nam/prod/nam.20210831/nam.t00z.awip1200.tm00.grib2 --output nam.t00z.awip1200.tm00.grib2'

and run it with ...

unixstr(unixstr)

With version R2017a it works fine. With version 2021a I get an error:

curl: (48) An unknown option was passed in to libcurl

The status returned is 48.

Executing with ! or system it still fails.

Any suggestions on what is the problem, and what is the workaround?

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John 2021-9-1

在 MATLAB Online 中打开

That was a typo, yes. I am executing ...

unix(unixstr)

Pounding on this some more with my local tech support we solved the problem. It is an issue with the libcurl library that ships with Matlab not matching the curl executable on the host. The workaround was to clear the LD_LIBRAY_PATH.

What we see, checking versions, is:

>> unix('/usr/bin/curl -V');
curl 7.29.0 (x86_64-redhat-linux-gnu) libcurl/7.72.0

which shows libcurl version 7.72.0 which is newer than the one on my local system (7.29.0).

I can clear that from the path by resetting LD_LIBRARY_PATH in my Matlab session, which then shows curl will use the older library matched to the executable:

>> unix('setenv LD_LIBRARY_PATH;/usr/bin/curl -V');
curl 7.29.0 (x86_64-redhat-linux-gnu) libcurl/7.29.0 NSS/3.44

Putting it all together, I prepend the setenv LD_LIBRARY_PATH command to the curl command before I execute it, and I can see the file is downloading

>> unixstr = 'setenv LD_LIBRARY_PATH ;/usr/bin/curl -k  https://nomads.ncep.noaa.gov/pub/data/nccf/com/nam/prod/nam.20210831/nam.t00z.awip1200.tm00.grib2 --output test.grib';
>> unix(unixstr);
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 28.2M  100 28.2M    0     0  9750k      0  0:00:02  0:00:02 --:--:-- 9749k
>> 

John 2021-9-1

I've always wondered why the "unix" and "system" commands don't execute in the same shell environment that launched Matlab? That would be the intent of a user in issuing such a command.

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