.\" DO NOT MODIFY THIS FILE!  It was generated by help2man 1.23.

.TH GPERF "1" "January 2017" "GNU gperf 3.1" FSF

.SH NAME

gperf \- generate a perfect hash function from a key set

.SH SYNOPSIS

.B gperf

[\fIOPTION\fR]... [\fIINPUT-FILE\fR]

.SH DESCRIPTION

GNU 'gperf' generates perfect hash functions.

.PP

If a long option shows an argument as mandatory, then it is mandatory

for the equivalent short option also.

.SS "Output file location:"

.HP

\fB\-\-output\-file\fR=\fIFILE\fR Write output to specified file.

.PP

The results are written to standard output if no output file is specified

or if it is -.

.SS "Input file interpretation:"

.TP

\fB\-e\fR, \fB\-\-delimiters\fR=\fIDELIMITER\-LIST\fR

Allow user to provide a string containing delimiters

used to separate keywords from their attributes.

Default is ",".

.TP

\fB\-t\fR, \fB\-\-struct\-type\fR

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.

.TP

\fB\-\-ignore\-case\fR

Consider upper and lower case ASCII characters as

equivalent. Note that locale dependent case mappings

are ignored.

.SS "Language for the output code:"

.TP

\fB\-L\fR, \fB\-\-language\fR=\fILANGUAGE\-NAME\fR

Generates code in the specified language. Languages

handled are currently C++, ANSI-C, C, and KR-C. The

default is ANSI-C.

.SS "Details in the output code:"

.TP

\fB\-K\fR, \fB\-\-slot\-name\fR=\fINAME\fR

Select name of the keyword component in the keyword

structure.

.TP

\fB\-F\fR, \fB\-\-initializer\-suffix\fR=\fIINITIALIZERS\fR

Initializers for additional components in the keyword

structure.

.TP

\fB\-H\fR, \fB\-\-hash\-function\-name\fR=\fINAME\fR

Specify name of generated hash function. Default is

\&'hash'.

.TP

\fB\-N\fR, \fB\-\-lookup\-function\-name\fR=\fINAME\fR

Specify name of generated lookup function. Default

name is 'in_word_set'.

.TP

\fB\-Z\fR, \fB\-\-class\-name\fR=\fINAME\fR

Specify name of generated C++ class. Default name is

\&'Perfect_Hash'.

.TP

\fB\-7\fR, \fB\-\-seven\-bit\fR

Assume 7-bit characters.

.TP

\fB\-l\fR, \fB\-\-compare\-lengths\fR

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.

.TP

\fB\-c\fR, \fB\-\-compare\-strncmp\fR

Generate comparison code using strncmp rather than

strcmp.

.TP

\fB\-C\fR, \fB\-\-readonly\-tables\fR

Make the contents of generated lookup tables

constant, i.e., readonly.

.TP

\fB\-E\fR, \fB\-\-enum\fR

Define constant values using an enum local to the

lookup function rather than with defines.

.TP

\fB\-I\fR, \fB\-\-includes\fR

Include the necessary system include file <string.h>

at the beginning of the code.

.TP

\fB\-G\fR, \fB\-\-global\-table\fR

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).

.TP

\fB\-P\fR, \fB\-\-pic\fR

Optimize the generated table for inclusion in shared

libraries.  This reduces the startup time of programs

using a shared library containing the generated code.

.TP

\fB\-Q\fR, \fB\-\-string\-pool\-name\fR=\fINAME\fR

Specify name of string pool generated by option \fB\-\-pic\fR.

Default name is 'stringpool'.

.TP

\fB\-\-null\-strings\fR

Use NULL strings instead of empty strings for empty

keyword table entries.

.TP

\fB\-\-constants\-prefix\fR=\fIPREFIX\fR

Specify prefix for the constants like TOTAL_KEYWORDS.

.TP

\fB\-W\fR, \fB\-\-word\-array\-name\fR=\fINAME\fR

Specify name of word list array. Default name is

\&'wordlist'.

.TP

\fB\-\-length\-table\-name\fR=\fINAME\fR

Specify name of length table array. Default name is

\&'lengthtable'.

.TP

\fB\-S\fR, \fB\-\-switch\fR=\fICOUNT\fR

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.

.TP

\fB\-T\fR, \fB\-\-omit\-struct\-type\fR

Prevents the transfer of the type declaration to the

output file. Use this option if the type is already

defined elsewhere.

.SS "Algorithm employed by gperf:"

.TP

\fB\-k\fR, \fB\-\-key\-positions\fR=\fIKEYS\fR

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.

.TP

\fB\-D\fR, \fB\-\-duplicates\fR

Handle keywords that hash to duplicate values. This

is useful for certain highly redundant keyword sets.

.TP

\fB\-m\fR, \fB\-\-multiple\-iterations\fR=\fIITERATIONS\fR

Perform multiple choices of the \fB\-i\fR and \fB\-j\fR 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.

.TP

\fB\-i\fR, \fB\-\-initial\-asso\fR=\fIN\fR

Provide an initial value for the associate values

array. Default is 0. Setting this value larger helps

inflate the size of the final table.

.TP

\fB\-j\fR, \fB\-\-jump\fR=\fIJUMP\-VALUE\fR

Affects the "jump value", i.e., how far to advance

the associated character value upon collisions. Must

be an odd number, default is 5.

.TP

\fB\-n\fR, \fB\-\-no\-strlen\fR

Do not include the length of the keyword when

computing the hash function.

.TP

\fB\-r\fR, \fB\-\-random\fR

Utilizes randomness to initialize the associated

values table.

.TP

\fB\-s\fR, \fB\-\-size\-multiple\fR=\fIN\fR

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.

.SS "Informative output:"

.TP

\fB\-h\fR, \fB\-\-help\fR

Print this message.

.TP

\fB\-v\fR, \fB\-\-version\fR

Print the gperf version number.

.TP

\fB\-d\fR, \fB\-\-debug\fR

Enables the debugging option (produces verbose

output to the standard error).

.SH AUTHOR

Written by Douglas C. Schmidt and Bruno Haible.

.SH "REPORTING BUGS"

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

.SH COPYRIGHT

Copyright \(co 1989-2017 Free Software Foundation, Inc.

License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

.br

This is free software: you are free to change and redistribute it.

There is NO WARRANTY, to the extent permitted by law.

.SH "SEE ALSO"

The full documentation for

.B gperf

is maintained as a Texinfo manual.  If the

.B info

and

.B gperf

programs are properly installed at your site, the command

.IP

.B info gperf

.PP

should give you access to the complete manual.