Extract part of file name using KornShell

I have a file name, for example: xxdatafile_20110120123030_12342.dat. I want to extract "XXdatafile_" from the file name.

How do I do that u开发者_运维百科sing Ksh on Unix?

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$ file=xxdatafile_20110120123030_12342.dat
$ echo ${file%%_*}
xxdatafile