NAME

       ctl - interface for examination and modification of the library’s internal state.

DESCRIPTION

       The CTL namespace is organized in a tree structure.  Starting from the root, each node can
       be either internal, containing other elements, or a leaf.  Internal nodes  themselves  can
       only  contain other nodes and cannot be entry points.  There are two types of those nodes:
       named and indexed.  Named nodes have  string  identifiers.   Indexed  nodes  represent  an
       abstract  array  index  and  have  an  associated  string identifier.  The index itself is
       provided by the user.  A collection of indexes present on the path of an  entry  point  is
       provided to the handler functions as name and index pairs.

       Entry  points  are  the  leaves of the CTL namespace structure.  Each entry point can read
       from the internal state, write to the internal state, exec a function or a combination  of
       these operations.

       The entry points are listed in the following format:

       name  | r(ead)w(rite)x(ecute) | global/- | read argument type | write argument type | exec
       argument type | config argument type

       A description  of  pmem_ctl  functions  can  be  found  on  the  following  manual  pages:
       libpmemblk_ctl_get(3), libpmemlog_ctl_get(3), libpmemobj_ctl_get(3)

CTL EXTERNAL CONFIGURATION

       In  addition  to  direct  function  call, each write entry point can also be set using two
       alternative methods.

       The first method is to load a configuration directly from the PMEMBLK_CONF/  PMEMLOG_CONF/
       PMEMOBJ_CONF  environment  variable.   A properly formatted ctl config string is a single-
       line sequence of queries separated by `;':

              query0;query1;...;queryN

       A single query is constructed from the name of the ctl write entry point and the argument,
       separated by `=':

              entry_point=entry_point_argument

       The  entry  point  argument type is defined by the entry point itself, but there are three
       predefined primitives:

              *) integer: represented by a sequence of [0-9] characters that form
                  a single number.
              *) boolean: represented by a single character: y/n/Y/N/0/1, each
                  corresponds to true or false. If the argument contains any
                  trailing characters, they are ignored.
              *) string: a simple sequence of characters.

       There are also complex argument types that are formed from the primitives separated  by  a
       `,':

              first_arg,second_arg

       In summary, a full configuration sequence looks like this:

              (first_entry_point)=(arguments, ...);...;(last_entry_point)=(arguments, ...);

       As an example, to set both prefault at_open and at_create variables:

              PMEMBLK_CONF="prefault.at_open=1;prefault.at_create=1"

       The  second  method  of loading an external configuration is to set the PMEMBLK_CONF_FILE/
       PMEMLOG_CONF_FILE/ PMEMOBJ_CONF_FILE environment variable to point to a file that contains
       a  sequence  of  ctl  queries.   The parsing rules are all the same, but the file can also
       contain white-spaces and comments.

       To create a comment, simply use `#' anywhere in a line and everything afterwards, until  a
       new line, will be ignored.

       An example configuration file:

              #########################
              # My pmemblk configuration
              #########################
              #
              # Global settings:
              prefault. # modify the behavior of pre-faulting
                  at_open = 1; # prefault when the pool is opened

              prefault.
                  at_create = 0; # but don't prefault when it's created

              # Per-pool settings:
              # ...

SEE ALSO

       libpmemblk_ctl_get(3), libpmemlog_ctl_get(3), libpmemobj_ctl_get(3) and <https://pmem.io>