COMMAND1; or COMMAND2
or is used to execute a command if the previous command was not successful
(returned a status of something other than 0).
or statements may be used as part of the condition in an and or while block. See
the documentation for if and while for examples.
or does not change the current exit status itself, but the command it runs most
likely will. The exit status of the last foreground command to exit can always
be accessed using the $status variable.
The following code runs the make command to build a program. If the build
succeeds, the program is installed. If either step fails, make clean is run,
which removes the files created by the build process.
make; and make install; or make clean