DragonFly On-Line Manual Pages

ODO(1)                                                                  ODO(1)

NAME
       odo - an atomic odometer for the command line

SYNOPSIS
       odo [-c | -i | -r | -s COUNT] [-p] file

DESCRIPTION
       odo atomically updates a count in a file, which will be created if not
       present. The count is text-formatted (e.g. "00012345\n"), and will be
       accurately incremented or reset even when multiple processes attempt to
       change the counter at the same time. (It uses memory mapping and atomic
       compare-and-swap operations to eliminate race conditions.)

       This could be used to track some intermittent event, like services
       being restarted. Since the counter is just a number in a text file,
       it's easy ls to compose odo with other tools.

OPTIONS
       These options impact how the counter is updated:

       -c     Print the current counter value without updating.

       -i     Increment the counter. (This is the default.)

       -r     Reset the counter to 0.

       -s COUNT
              Update the counter to a specific value.

       -p     Print the new value of the counter after updating.

EXIT STATUS
       Returns 0 if the counter has been successfully updated. Returns 1 if
       the file could not be read, created, or written, or if its current
       contents do not match the expected format of a counter file.

EXAMPLES
       This atomically increments a counter in /log/restarts. If the counter
       file does not exist, it is created as 0 and incremented to 1.

           $ odo /log/restarts

       Same, but print the updated count:

           $ odo -p /log/restarts

       Reset the count to 0:

           $ ./odo -r /log/restarts

       Set the count to a number (for testing notifications, perhaps):

           $ ./odo -s 12345 /log/restarts

       Print the current counter value without incrementing:

           $ ./odo -c /log/restarts

       Print usage / help:

           $ ./odo -h

BUGS
       odo's atomicity is only as reliable as the underlying filesystem's.
       Inconsistencies may still occur if used on a non-local filesystems such
       as nfs.

COPYRIGHT
       odo is Copyright (C) 2014 Scott Vokes scott.vokes@atomicobject.com.

SEE ALSO
       runit(8), sqlite3(1), nfsd(8)

                                 November 2014                          ODO(1)