DERP(1)                                                   DERP(1)

     NAME
          derp - directory-examining recursive compare

     SYNOPSIS
          derp [ -qcutDL ] [ -p perms ] myfile oldfile yourfile

     DESCRIPTION
          Derp recursively compares the two directories myfile and
          yourfile using a third common backup directory oldfile as
          reference. The changes found are printed to standard output,
          one per line, with the file status describing either sides
          actions followed by tabulator and the relative file path
          which might be empty in case when the changed files refers
          to the ones given at program arguments.

          The possible status codes:

          an   File added in myfile

          na   File added in yourfile

          aa!  Both sides added different files with the same name

          mn   File was modified in myfile

          nm   File was modified in yourfile

          mm!  File was changed differently in myfile and yourfile

          dn   File was deleted in myfile

          nd   File was deleted in yourfile

          md!  File was modified in myfile but deleted in yourfile

          dm!  File was modified in yourfile but deleted in myfile

          Errors are printed to standard error unless -q option is
          specified. The program is terminated when errors are encoun-
          tered unless the -c option is given. This can be useful if
          files are not accessible due to file permission or media
          corruption.

          The -u option will consider changes of file owner and group.
          When omitted, file ownership is ignored.

          The -p option sets the octal mask perms of bits to check in
          the file permissions. The default ignores file permissions.

          When modification times are comparable then the -t option

     DERP(1)                                                   DERP(1)

          can be used to quickly find changes. If specified, files are
          considered unchanged if the name, file size and the modifi-
          cation time matches. This is useful when comparing /n/dump
          archives on the same fileserver.

          Files are considered the same if they are from the same
          mount and their qid (see stat(5)) matches. For directories,
          the access time is also compared. If the access time was
          disabled on the fileserver, then all directories need to be
          compared using the -D option.

          Some filesystems like hgfs(4) do not always return exact
          file size in stat, so the length check can be disabled with
          the -L option.

     SOURCE
          /sys/src/cmd/derp.c

     SEE ALSO
          cmp(1), diff(1), history(1), fs(4), hgfs(4)

     DIAGNOSTICS
          The exit status is set to 'errors' when errors were encoun-
          tered.

     HISTORY
          Derp first appeared in 9front (November, 2012).