Monday, October 18, 2010

Bash loops

Faced with having to write 160 commands by hand (to split 5000 files into subdirectories, based on the first 3 digits of their 6 digit filenames) I quickly learnt bash loops instead:

for i in `seq 102 189`;
    mkdir $i
    mv $i???.sgf $i/

I.e. it does commands like this:
mkdir 102
  mv 102???.sgf 102/
  mkdir 103
  mv 103???.sgf 103/

UPDATE: In a comment, traxplayer kindly explained how I would make, for instance a filename like 120abc.txt; obviously writing $iabc.txt won't work. The trick is to write $i as ${i}. E.g.
mv ${i}abc.sgf $i/

I just needed to use it, and it worked! This bash script tries to find the last reference to each of XXX06..XXX20 in two logfiles.
rm lastorder.log
touch lastorder.log

for i in `seq 6 9`;
        grep -h XXX0${i} order_verbose.log.old order_verbose.log | tail -1 >> lastorder.log

for i in `seq 10 20`;
        grep -h XXX${i} order_verbose.log.old order_verbose.log | tail -1 >> lastorder.log

By the way, traxplayer also said he prefers to use $(...) instead of `...` for readability:
  for i in $(seq 102 189);

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