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 GPERF(1)                      GNU gperf 3.0.4                      GPERF(1)
 FSF                                                                     FSF

                                February 2009

      gperf - generate a perfect hash function from a key set

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

      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.

           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

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 GPERF(1)                      GNU gperf 3.0.4                      GPERF(1)
 FSF                                                                     FSF

                                February 2009

           Specify name of generated lookup function. Default name is

      -Z, --class-name=NAME
           Specify name of generated C++ class. Default name is

      -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 comparisons 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.,

      -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 hiding 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 'stringpool'.

           Use NULL strings instead of empty strings for empty keyword table

      -W, --word-array-name=NAME

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 GPERF(1)                      GNU gperf 3.0.4                      GPERF(1)
 FSF                                                                     FSF

                                February 2009

           Specify name of word list array. Default name is 'wordlist'.

           Specify name of length table array. Default name is

      -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
           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

      -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.

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 GPERF(1)                      GNU gperf 3.0.4                      GPERF(1)
 FSF                                                                     FSF

                                February 2009

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

      -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
           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).

      Written by Douglas C. Schmidt and Bruno Haible.

      Report bugs to <>.

      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

      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

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 GPERF(1)                      GNU gperf 3.0.4                      GPERF(1)
 FSF                                                                     FSF

                                February 2009

      should give you access to the complete manual.

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