Linux batch "export" options

[Bill B]

I saw some example batch programs that had lines like...
export SORTIN=sort/TESTSORT.IN[RECFM=FT,LRECL=80]

I specified a LRECL and BLKSIZE in my DCB but only gave a filename in the export, none of those extra export file options within the brackets...if that's what they are? It seemed to work. Do they serve a purpose?

Thanks,

Bill