[Swift-user] Unix find as external mapper

[Neil Best]

I tried to use find as an external mapper in a way that seemed fairly
natural to me:

file monthly[] <ext; exec="find data/nc -mindepth 1 -type d -printf
'[%f] %p.nc\n'\|.txt'">;

When I run this find by itself at the command line the output looks like this:

$ find data/nc -mindepth 1 -type d -printf '[%f] %p.nc\n' | head
[197901] data/nc/197901.nc
[197903] data/nc/197903.nc
[197904] data/nc/197904.nc
[197902] data/nc/197902.nc
[197905] data/nc/197905.nc
[197906] data/nc/197906.nc
[197907] data/nc/197907.nc
[197908] data/nc/197908.nc
[197909] data/nc/197909.nc
[197910] data/nc/197910.nc

The find actually looks at directories.  These .nc files don't exist
yet, but each one will be an aggregation of the .nc files within the
folder of the same name using this command:

cdo mergetime data/nc/197901/*.single.nc data/nc/197901.nc

I thought I could then do a nested foreach over years and months to
execute the invocations.

I presume that the external mapper is treating the exec argument as a
command name and not parsing the arguments.  Using the other
parameters in the ext construct would force me to write a wrapper
script for the find invocation since all of the arguments must have
names apparently.

Do I have this right?  Maybe there is a more straightforward approach.