Provided by: locate_4.4.2-1ubuntu3_i386 bug

NAME

       locatedb - front-compressed file name database

DESCRIPTION

       This  manual  page  documents the format of file name databases for the
       GNU version of locate.  The file name databases contain lists of  files
       that  were  in  particular directory trees when the databases were last
       updated.

       There can be multiple databases.   Users  can  select  which  databases
       locate  searches  using an environment variable or command line option;
       see locate(1).  The system administrator can choose the  file  name  of
       the  default  database,  the  frequency  with  which  the databases are
       updated, and the directories for which they contain entries.  Normally,
       file  name  databases  are  updated  by  running  the  updatedb program
       periodically, typically nightly; see updatedb(1).

GNU LOCATE02 database format

       This is the default format of  databases  produced  by  updatedb.   The
       updatedb  program  runs frcode to compress the list of file names using
       front-compression, which reduces the database size by a factor of 4  to
       5.   Front-compression  (also  known  as incremental encoding) works as
       follows.

       The database entries are a sorted list (case-insensitively, for  users'
       convenience).   Since the list is sorted, each entry is likely to share
       a prefix (initial string) with the previous entry.  Each database entry
       begins  with  an  signed  offset-differential  count byte, which is the
       additional number of characters of prefix of the preceding entry to use
       beyond the number that the preceding entry is using of its predecessor.
       (The counts can be negative.)  Following the count is a null-terminated
       ASCII remainder -- the part of the name that follows the shared prefix.

       If  the  offset-differential  count  is  larger than can be stored in a
       signed byte (+/-127), the byte has the value 0x80 (binary 10000000) and
       the  actual  count  follows  in a 2-byte word, with the high byte first
       (network byte order).  This count can also be negative  (the  sign  bit
       being in the first of the two bytes).

       Every  database begins with a dummy entry for a file called `LOCATE02',
       which locate checks for to  ensure  that  the  database  file  has  the
       correct format; it ignores the entry in doing the search.

       Databases  can  not be concatenated together, even if the first (dummy)
       entry is trimmed from all but the first database.  This is because  the
       offset-differential  count  in  the  first  entry  of  the  second  and
       following databases will be wrong.

       In the future, the data within the locate database may not be sorted in
       any  particular  order.   To  obtain sorted results, pipe the output of
       locate through sort -f.

slocate database format

       The slocate program uses a database format similar to,  but  not  quite
       the  same as, GNU locate.  The first byte of the database specifies its
       security level.  If the security level is 0, slocate will  read,  match
       and  print  filenames  on  the basis of the information in the database
       only.  However, if the security level byte is 1, slocate omits  entries
       from  its  output  if  the invoking user is unable to access them.  The
       second byte of the database is zero.  The second byte  is  followed  by
       the  first  database  entry.   The  first  entry in the database is not
       preceded by  any  differential  count  or  dummy  entry.   Instead  the
       differential count for the first item is assumed to be zero.

       Starting  with  the  second  entry  (if  any)  in the database, data is
       interpreted as for the GNU LOCATE02 format.

Old Locate Database format

       There is also an old database format, used  by  Unix  locate  and  find
       programs  and earlier releases of the GNU ones.  updatedb runs programs
       called bigram and code to produce old-format databases.  The old format
       differs  from  the above description in the following ways.  Instead of
       each entry starting with an offset-differential count byte  and  ending
       with a null, byte values from 0 through 28 indicate offset-differential
       counts from -14 through 14.  The byte  value  indicating  that  a  long
       offset-differential  count  follows  is  0x1e (30), not 0x80.  The long
       counts are stored in host byte order, which is not necessarily  network
       byte order, and host integer word size, which is usually 4 bytes.  They
       also represent a count 14 less than their value.   The  database  lines
       have  no  termination  byte; the start of the next line is indicated by
       its first byte having a value <= 30.

       In addition, instead of starting with a dummy entry, the  old  database
       format  starts  with  a  256  byte table containing the 128 most common
       bigrams in the file list.  A bigram is a pair of adjacent bytes.  Bytes
       in  the  database that have the high bit set are indexes (with the high
       bit cleared) into the bigram table.  The bigram and offset-differential
       count  coding makes these databases 20-25% smaller than the new format,
       but makes them not 8-bit clean.  Any byte in a file name that is in the
       ranges  used  for  the  special  codes is replaced in the database by a
       question mark, which not coincidentally is the shell wildcard to  match
       a single character.

EXAMPLE

       Input to frcode:
       /usr/src
       /usr/src/cmd/aardvark.c
       /usr/src/cmd/armadillo.c
       /usr/tmp/zoo

       Length of the longest prefix of the preceding entry to share:
       0 /usr/src
       8 /cmd/aardvark.c
       14 rmadillo.c
       5 tmp/zoo

       Output  from  frcode, with trailing nulls changed to newlines and count
       bytes made printable:
       0 LOCATE02
       0 /usr/src
       8 /cmd/aardvark.c
       6 rmadillo.c
       -9 tmp/zoo

       (6 = 14 - 8, and -9 = 5 - 14)

SEE ALSO

       find(1), locate(1), locatedb(5), xargs(1), Finding  Files  (on-line  in
       Info, or printed)

BUGS

       The   best   way   to   report   a   bug   is   to   use  the  form  at
       http://savannah.gnu.org/bugs/?group=findutils.  The reason for this  is
       that  you  will  then  be able to track progress in fixing the problem.
       Other comments about locate(1)  and  about  the  findutils  package  in
       general  can  be  sent  to the bug-findutils mailing list.  To join the
       list, send email to bug-findutils-request@gnu.org.

                                                                   LOCATEDB(5)