= mtbl_merge(1) =

== NAME ==

mtbl_merge - merge MTBL data from multiple input files into a single output file

== SYNOPSIS ==

User-provided functions:

[verse]
^typedef void *
(*mtbl_merge_init_func)(void);^

[verse]
^typedef void
(*mtbl_merge_free_func)(void *clos);^

[verse]
^typedef void
(*mtbl_merge_func)(void *'clos',
        const uint8_t *'key', size_t 'len_key',
        const uint8_t *'val0', size_t 'len_val0',
        const uint8_t *'val1', size_t 'len_val1',
        uint8_t **'merged_val', size_t *'len_merged_val');^

Command line tool:

[verse]
^export MTBL_MERGE_DSO="'libexample.so.0'"^
^export MTBL_MERGE_FUNC_PREFIX="'example_merge'"^
^mtbl_merge^ 'INPUT' ['INPUT']... 'OUTPUT'

== DESCRIPTION ==

^mtbl_merge^(1) is a command-line driver for the ^mtbl_merger^(3) interface.
The ^mtbl_merger^(3) interface requires a user-provided merge function, which
is loaded from a shared object whose filename is specified in the environment
variable 'MTBL_MERGE_DSO'.

The user-provided merge function must have the same type as the
'mtbl_merge_func' function type given above in the synopsis. The symbol name
of the merge function to be loaded from the user-provided DSO will be
constructed by appending "_func" to the string provided in the
'MTBL_MERGE_FUNC_PREFIX' environment variable, which must be non-empty.

Additionally, two optional functions may be provided: an "init" function whose
symbol name is "_init" appended to the function prefix, and a "free" function
whose symbol name is "_free" appended to the function prefix. If the "init"
function exists, it will be called at the beginning, before any calls to the
merge function, and the return value from the init function will be passed as
the first argument to the merge function. If the "free" function exists, it will
be called at the end, after any calls to the merge function, and its argument
will be the return value of the "init" function.

The environment variable 'MTBL_MERGE_BLOCK_SIZE' may optionally be set in order
to configure the MTBL block size (in bytes) of the output file.

== SEE ALSO ==

^mtbl_merger^(3)
