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CentOS 7.0 - man page for gperf (centos section 1)

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GPERF(1)				       FSF					 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.

   Output file location:
       --output-file=FILE Write output to specified file.

       The results are written to standard output if no output file is specified or if it is -.

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

       -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.

       --ignore-case
	      Consider	upper  and  lower  case  ASCII characters as equivalent. Note that locale
	      dependent case mappings are ignored.

   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-function-name=NAME
	      Specify name of generated hash function. Default is 'hash'.

       -N, --lookup-function-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 'Perfect_Hash'.

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

       -l, --compare-lengths
	      Compare  key  lengths  before  trying a string comparison. This is necessary if the
	      keywords contain NUL bytes. It also helps cut down on the number of string  compar-
	      isons made during the lookup.

       -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.

       -E, --enum
	      Define  constant values using an enum local to the lookup function rather than with
	      defines.

       -I, --includes
	      Include the necessary system include file <string.h> at the beginning of the code.

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

       -P, --pic
	      Optimize	the  generated table for inclusion in shared libraries.  This reduces the
	      startup time of programs using a shared library containing the generated code.

       -Q, --string-pool-name=NAME
	      Specify name of string pool generated by option --pic.  Default  name  is  'string-
	      pool'.

       --null-strings
	      Use NULL strings instead of empty strings for empty keyword table entries.

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

       --length-table-name=NAME
	      Specify name of length table array. Default name is 'lengthtable'.

       -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 gener-
	      ated.  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 table, 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 allowable choices range
	      between 1-255, 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.

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

       -m, --multiple-iterations=ITERATIONS
	      Perform multiple choices of the -i and -j values, and choose the best results. This
	      increases the running time by a factor of ITERATIONS but does a good job minimizing
	      the generated table size.

       -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 associated character value
	      upon collisions. Must be an odd number, default is 5.

       -n, --no-strlen
	      Do not include the length of the keyword when computing the hash function.

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

       -s, --size-multiple=N
	      Affects the size of the generated hash table. The numeric argument N indicates "how
	      many times larger or smaller" the associated 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
	      1/3 means "make the maximum associated value about 3 times smaller than the  number
	      of  input keys". A larger table should decrease the time required for an unsuccess-
	      ful 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).

AUTHOR
       Written by Douglas C. Schmidt and Bruno Haible.

REPORTING BUGS
       Report bugs to <bug-gnu-gperf@gnu.org>.

COPYRIGHT
       Copyright (C) 1989-1998, 2000-2004, 2006-2007, 2009 Free Software Foundation, Inc.
       This is free software; see the source for copying conditions.  There is NO  warranty;  not
       even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

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 3.0.4 			  February 2009 				 GPERF(1)
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