Yesterday, I needed to clobber a bunch of similarly-named database schemas on my development machine. I could have selected and deleted 40 times in Navicat, but I thought I’d try to write a one-liner instead:

`

mysql -u root -e “show databases;” | grep _3_6 | xargs -IDB_NAME mysql -u root -e “drop database DB_NAME;”
`

The first part pulls the database names all the database names. The second part culls any schema names that don’t match “_3_6”, and the last part executes a DROP DATABASE command for each matching schema name.

The clever bit is the “-I” flag to xargs, which sets a token to be replaced with the argument in the command string. In this case, the schema name (“pp_development_3_6”) is dropped in wherever xargs sees the string “DB_NAME” in the command.

_Wikipedia attributes the xargs utility to PWB/UNIX. It may have been written by Dick Haight, who is, apparently, the 10 of Clubs in the Unix 25th Anniversary Playing Card deck, which, apparently, exists.
_