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gperf(1)

NAME

       gperf - generate a perfect hash function from a key set

SYNOPSIS

       gperf [OPTION]... [INPUT-FILE]

DESCRIPTION

       GNU `gperf' generates perfect hash functions.

       If  a  long option shows an argument as mandatory, then it is mandatory
       for the equivalent short option also.

   Input file interpretation:
       -e, --delimiters=DELIMITER-LIST
	      Allow user to provide a string  containing  delimiters  used  to
	      separate keywords from their attributes.	Default is ",\n".

       -t, --struct-type
	      Allows  the  user  to  include a structured type declaration for
	      generated code. Any text before %% is  considered  part  of  the
	      type  declaration.  Key  words  and additional fields may follow
	      this, one group of fields per line.

   Language for the output code:
       -L, --language=LANGUAGE-NAME
	      Generates code in the specified language. Languages handled  are
	      currently C++, ANSI-C, C, and KR-C. The default is C.

   Details in the output code:
       -K, --slot-name=NAME
	      Select name of the keyword component in the keyword structure.

       -F, --initializer-suffix=INITIALIZERS
	      Initializers for additional components in the keyword structure.

       -H, --hash-fn-name=NAME
	      Specify name of generated hash function. Default is `hash'.

       -N, --lookup-fn-name=NAME
	      Specify name of  generated  lookup  function.  Default  name  is
	      `in_word_set'.

       -Z, --class-name=NAME
	      Specify  name  of  generated  C++  class.  Default name is `Per-
	      fect_Hash'.

       -7, --seven-bit
	      Assume 7-bit characters.

       -c, --compare-strncmp
	      Generate comparison code using strncmp rather than strcmp.

       -C, --readonly-tables
	      Make the contents of generated  lookup  tables  constant,  i.e.,
	      readonly.

       -G, --global
	      Generate	the  static table of keywords as a static global vari-
	      able, rather than hiding it inside of the lookup function (which
	      is the default behavior).

       -W, --word-array-name=NAME
	      Specify name of word list array. Default name is `wordlist'.

       -S, --switch=COUNT
	      Causes  the  generated  C code to use a switch statement scheme,
	      rather than an array lookup table.  This can lead to a reduction
	      in both time and space requirements for some keyfiles. The COUNT
	      argument determines how many switch statements are generated.  A
	      value  of  1  generates  1 switch containing all the elements, a
	      value of 2 generates 2 tables with 1/2 the elements in each  ta-
	      ble,  etc.  If COUNT is very large, say 1000000, the generated C
	      code does a binary search.

       -T, --omit-struct-type
	      Prevents the transfer of the  type  declaration  to  the	output
	      file.  Use this option if the type is already defined elsewhere.

   Algorithm employed by gperf:
       -k, --key-positions=KEYS
	      Select the key positions used in the hash function.  The	allow-
	      able  choices range between 1-126, inclusive.  The positions are
	      separated by commas, ranges may be used, and key	positions  may
	      occur  in  any  order.   Also, the meta-character '*' causes the
	      generated hash function to consider ALL  key  positions,	and  $
	      indicates  the ``final character'' of a key, e.g., $,1,2,4,6-10.

       -l, --compare-strlen
	      Compare key lengths before  trying  a  string  comparison.  This
	      helps  cut  down on the number of string comparisons made during
	      the lookup.

       -D, --duplicates
	      Handle keywords that hash to duplicate values.  This  is	useful
	      for certain highly redundant keyword sets.

       -f, --fast=ITERATIONS
	      Generate	the  gen-perf.hash  function  ``fast''. This decreases
	      gperf's running time at the cost of minimizing  generated  table
	      size.  The  numeric  argument  represents the number of times to
	      iterate when resolving a collision. `0' means ``iterate  by  the
	      number of keywords''.

       -i, --initial-asso=N
	      Provide an initial value for the associate values array. Default
	      is 0. Setting this value larger helps inflate the  size  of  the
	      final table.

       -j, --jump=JUMP-VALUE
	      Affects the ``jump value'', i.e., how far to advance the associ-
	      ated character value upon collisions. Must  be  an  odd  number,
	      default is 5.

       -r, --random
	      Utilizes randomness to initialize the associated values table.

       -s, --size-multiple=N
	      Affects  the size of the generated hash table. The numeric argu-
	      ment N indicates ``how many times larger or smaller'' the  asso-
	      ciated  value  range should be, in relationship to the number of
	      keys, e.g. a value of 3 means  ``allow  the  maximum  associated
	      value  to  be  about  3  times  larger  than the number of input
	      keys.'' Conversely, a value of -3 means ``make the maximum asso-
	      ciated  value  about  3  times  smaller than the number of input
	      keys. A larger table should decrease the time  required  for  an
	      unsuccessful  search,  at  the  expense  of  extra  table space.
	      Default value is 1.

   Informative output:
       -h, --help
	      Print this message.

       -v, --version
	      Print the gperf version number.

       -d, --debug
	      Enables the debugging option (produces  verbose  output  to  the
	      standard error).

REPORTING BUGS

       Report bugs to <bug-gnu-utils@gnu.org>.

SEE ALSO

       The full documentation for gperf is maintained as a Texinfo manual.  If
       the info and gperf programs are properly installed at  your  site,  the
       command

	      info gperf

       should give you access to the complete manual.

GNU gperf 2.7.2 		September 2000			      GPERF(1)

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