If you've botched an SVN log entry (typo, etc.), you can fix it as follows:

$ echo "Here is the new, correct log message" > newlog.txt
$ svnadmin setlog myrepos newlog.txt -r 388

Given a log file with a date in the first column, chop up the file into separate file:

$ awk '/^[0-9]/ {print $0 > $1".log"}' logfile.txt

If you have a string that has characters that the shell won't like, you can do a substitution on them:

$ awk '{gsub("/","_",$1); print $1 > $1".log"}' logfile.txt