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/home/swipl/lib/swipl/library/mqi.pl
AllApplicationManualNameSummaryHelp

  • swipl
    • library
      • error.pl -- Error generating support
      • apply.pl -- Apply predicates on a list
      • lists.pl -- List Manipulation
      • debug.pl -- Print debug messages and test assertions
      • broadcast.pl -- Event service
      • socket.pl -- Network socket (TCP and UDP) library
      • predicate_options.pl -- Access and analyse predicate options
      • shlib.pl -- Utility library for loading foreign objects (DLLs, shared objects)
      • option.pl -- Option list processing
      • uid.pl
      • unix.pl -- Unix specific operations
      • syslog.pl -- Unix syslog interface
      • thread_pool.pl -- Resource bounded thread management
      • gensym.pl -- Generate unique symbols
      • settings.pl -- Setting management
      • arithmetic.pl -- Extensible arithmetic
      • main.pl -- Provide entry point for scripts
      • readutil.pl -- Read utilities
      • ssl.pl -- Secure Socket Layer (SSL) library
      • crypto.pl -- Cryptography and authentication library
      • filesex.pl -- Extended operations on files
      • doc_http.pl -- Documentation server
      • pldoc.pl -- Process source documentation
      • operators.pl -- Manage operators
      • pairs.pl -- Operations on key-value lists
      • prolog_source.pl -- Examine Prolog source-files
      • sgml.pl -- SGML, XML and HTML parser
      • quasi_quotations.pl -- Define Quasi Quotation syntax
      • uri.pl -- Process URIs
      • url.pl -- Analysing and constructing URL
      • www_browser.pl -- Open a URL in the users browser
      • prolog_colour.pl -- Prolog syntax colouring support.
      • record.pl -- Access compound arguments by name
      • prolog_xref.pl -- Prolog cross-referencer data collection
      • occurs.pl -- Finding and counting sub-terms
      • ordsets.pl -- Ordered set manipulation
      • assoc.pl -- Binary associations
      • ugraphs.pl -- Graph manipulation library
      • memfile.pl
      • xpath.pl -- Select nodes in an XML DOM
      • iostream.pl -- Utilities to deal with streams
      • atom.pl -- Operations on atoms
      • porter_stem.pl
      • solution_sequences.pl -- Modify solution sequences
      • prolog_pack.pl -- A package manager for Prolog
      • prolog_config.pl -- Provide configuration information
      • process.pl -- Create processes and redirect I/O
      • git.pl -- Run GIT commands
      • ctypes.pl -- Character code classification
      • time.pl -- Time and alarm library
      • utf8.pl -- UTF-8 encoding/decoding on lists of character codes.
      • base64.pl -- Base64 encoding and decoding
      • sha.pl -- SHA secure hashes
      • crypt.pl
      • persistency.pl -- Provide persistent dynamic predicates
      • pure_input.pl -- Pure Input from files and streams
      • nb_set.pl -- Non-backtrackable sets
      • xsdp_types.pl -- XML-Schema primitive types
      • uuid.pl -- Universally Unique Identifier (UUID) Library
      • pcre.pl -- Perl compatible regular expression matching for SWI-Prolog
      • aggregate.pl -- Aggregation operators on backtrackable predicates
      • rdf_write.pl -- Write RDF/XML from a list of triples
      • rdf.pl -- RDF/XML parser
      • sgml_write.pl -- XML/SGML writer module
      • archive.pl -- Access several archive formats
      • csv.pl -- Process CSV (Comma-Separated Values) data
      • dialect.pl -- Support multiple Prolog dialects
      • apply_macros.pl -- Goal expansion rules to avoid meta-calling
      • prolog_code.pl -- Utilities for reasoning about code
      • dif.pl -- The dif/2 constraint
      • thread.pl -- High level thread primitives
      • rdf_triple.pl -- Create triples from intermediate representation
      • rdf_parser.pl
      • rewrite_term.pl
      • rbtrees.pl -- Red black trees
      • nb_rbtrees.pl -- Non-backtrackable operations on red black trees
      • pengines.pl -- Pengines: Web Logic Programming Made Easy
      • yall.pl -- Lambda expressions
      • sandbox.pl -- Sandboxed Prolog code
      • prolog_format.pl -- Analyse format specifications
      • random.pl -- Random numbers
      • pengines_io.pl -- Provide Prolog I/O for HTML clients
      • zlib.pl -- Zlib wrapper for SWI-Prolog
      • bdb.pl -- Berkeley DB interface
      • hash_stream.pl -- Maintain a hash on a stream
      • md5.pl -- MD5 hashes
      • pprint.pl -- Pretty Print Prolog terms
      • modules.pl -- Module utility predicates
      • lazy_lists.pl -- Lazy list handling
      • edinburgh.pl -- Some traditional Edinburgh predicates
      • prolog_clause.pl -- Get detailed source-information about a clause
      • prolog_breakpoints.pl -- Manage Prolog break-points
      • dicts.pl -- Dict utilities
      • backcomp.pl -- Backward compatibility
      • paxos.pl -- A Replicated Data Store
      • doc_latex.pl -- PlDoc LaTeX backend
      • system.pl -- System utilities
      • quintus.pl -- Quintus compatibility
      • prolog_debug.pl -- User level debugging tools
      • streampool.pl -- Input multiplexing
      • stomp.pl -- STOMP client.
      • date.pl -- Process dates and times
      • statistics.pl -- Get information about resource usage
      • listing.pl -- List programs and pretty print clauses
      • snowball.pl -- The Snowball multi-lingual stemmer library
      • unicode.pl -- Unicode string handling
      • heaps.pl -- heaps/priority queues
      • files.pl
      • optparse.pl -- command line parsing
      • threadutil.pl -- Interactive thread utilities
      • edit.pl -- Editor interface
      • help.pl -- Text based manual
      • fastrw.pl -- Fast reading and writing of terms
      • redis.pl -- Redis client
      • prolog_stack.pl -- Examine the Prolog stack
      • editline.pl -- BSD libedit based command line editing
      • odbc.pl
      • jpl.pl -- A Java interface for SWI Prolog 7.x
      • zip.pl -- Access resource ZIP archives
      • hashtable.pl -- Hash tables
      • ansi_term.pl -- Print decorated text to ANSI consoles
      • isub.pl -- isub: a string similarity measure
      • terms.pl -- Term manipulation
      • check.pl -- Consistency checking
      • prolog_codewalk.pl -- Prolog code walker
      • prolog_autoload.pl -- Autoload all dependencies
      • shell.pl -- Elementary shell commands
      • wfs.pl -- Well Founded Semantics interface
      • portray_text.pl -- Portray text
      • prolog_jiti.pl -- Just In Time Indexing (JITI) utilities
      • strings.pl -- String utilities
      • plunit.pl -- Unit Testing
      • xmlenc.pl -- XML encryption library
      • prolog_metainference.pl -- Infer meta-predicate properties
      • c14n2.pl -- C14n2 canonical XML documents
      • charsio.pl -- I/O on Lists of Character Codes
      • make.pl -- Reload modified source files
      • writef.pl -- Old-style formatted write
      • qsave.pl -- Save current program as a state or executable
      • sort.pl
      • tables.pl -- XSB interface to tables
      • varnumbers.pl -- Utilities for numbered terms
      • when.pl -- Conditional coroutining
      • intercept.pl -- Intercept and signal interface
      • term_to_json.pl
      • mqi.pl
        • mqi_start/1
        • mqi_version/2
        • mqi_start/0
        • mqi_stop/1
      • increval.pl -- Incremental dynamic predicate modification
      • explain.pl -- Describe Prolog Terms
      • prolog_wrap.pl -- Wrapping predicates
      • win_menu.pl -- Console window menu
      • tty.pl -- Terminal operations
      • test_cover.pl -- Clause coverage analysis
      • table.pl
      • udp_broadcast.pl -- A UDP broadcast proxy
      • xmldsig.pl -- XML Digital signature
      • redis_streams.pl -- Using Redis streams
      • yaml.pl -- Process YAML data
      • prolog_trace.pl -- Print access to predicates
      • prolog_stream.pl -- A stream with Prolog callbacks
      • base32.pl -- Base32 encoding and decoding
      • doc_files.pl -- Create stand-alone documentation files
      • prolog_history.pl -- Per-directory persistent commandline history
      • readline.pl -- GNU readline interface
      • coinduction.pl -- Co-Logic Programming
      • codesio.pl -- I/O on Lists of Character Codes
      • protobufs.pl -- Google's Protocol Buffers ("protobufs")
      • rlimit.pl
      • double_metaphone.pl -- Phonetic string matching
      • oset.pl -- Ordered set manipulation
      • cgi.pl -- Read CGI parameters
      • pdt_console.pl
      • pwp.pl -- Prolog Well-formed Pages
 mqi_start(+Options:list) is semidet
Starts a Prolog Machine Query Interface ('MQI') using Options. The MQI is normally started automatically by a library built for a particular programming language such as the swiplserver Python library, but starting manually can be useful when debugging Prolog code in some scenarios. See the documentation on "Standalone Mode" for more information.

Once started, the MQI listens for TCP/IP or Unix Domain Socket connections and authenticates them using the password provided (or created depending on options) before processing any messages. The messages processed by the MQI are described below.

For debugging, the server outputs traces using the debug/3 predicate so that the server operation can be observed by using the debug/1 predicate. Run the following commands to see them:

  • debug(mqi(protocol)): Traces protocol messages to show the flow of commands and connections. It is designed to avoid filling the screen with large queries and results to make it easier to read.
  • debug(mqi(query)): Traces messages that involve each query and its results. Therefore it can be quite verbose depending on the query. __Options__

    Options is a list containing any combination of the following options. When used in the Prolog top level (i.e. in Standalone Mode), these are specified as normal Prolog options like this:

    mqi_start([unix_domain_socket(Socket), password('a password')])

    When using "Embedded Mode" they are passed using the same name but as normal command line arguments like this:

    swipl --quiet -g mqi_start -t halt -- --write_connection_values=true
    --password="a password" --create_unix_domain_socket=true

    Note the use of quotes around values that could confuse command line processing like spaces (e.g. "a password") and that unix_domain_socket(Variable) is written as --create_unix_domain_socket=true on the command line. See below for more information.

  • port(?Port) The TCP/IP port to bind to on localhost. This option is ignored if the unix_domain_socket/1 option is set. Port is either a legal TCP/IP port number (integer) or a variable term like Port. If it is a variable, it causes the system to select a free port and unify the variable with the selected port as in tcp_bind/2. If the option write_connection_values(true) is set, the selected port is output to STDOUT followed by \n on startup to allow the client language library to retrieve it in "Embedded Mode".
  • unix_domain_socket(?Unix_Domain_Socket_Path_And_File) If set, Unix Domain Sockets will be used as the way to communicate with the server. Unix_Domain_Socket_Path_And_File specifies the fully qualified path and filename to use for the socket.

    To have one generated instead (recommended), pass Unix_Domain_Socket_Path_And_File as a variable when calling from the Prolog top level and the variable will be unified with a created filename. If launching in "Embedded Mode", instead pass --create_unix_domain_socket=true since there isn't a way to specify variables from the command line. When generating the file, a temporary directory will be created using tmp_file/2 and a socket file will be created within that directory following the below requirements. If the directory and file are unable to be created for some reason, mqi_start/1 fails.

    Regardless of whether the file is specified or generated, if the option write_connection_values(true) is set, the fully qualified path to the generated file is output to STDOUT followed by \n on startup to allow the client language library to retrieve it.

    Specifying a file to use should follow the same guidelines as the generated file:

    • If the file exists when the MQI is launched, it will be deleted.
    • The Prolog process will attempt to create and, if Prolog exits cleanly, delete this file (and directory if it was created) when the MQI closes. This means the directory from a specified file must have the appropriate permissions to allow the Prolog process to do so.
    • For security reasons, the filename should not be predictable and the directory it is contained in should have permissions set so that files created are only accessible to the current user.
    • The path must be below 92 bytes long (including null terminator) to be portable according to the Linux documentation.
  • password(?Password) The password required for a connection. If not specified (recommended), the MQI will generate one as a Prolog string type since Prolog atoms are globally visible (be sure not to convert to an atom for this reason). If Password is a variable it will be unified with the created password. Regardless of whether the password is specified or generated, if the option write_connection_values(true) is set, the password is output to STDOUT followed by \n on startup to allow the client language library to retrieve it. This is the recommended way to integrate the MQI with a language as it avoids including the password as source code. This option is only included so that a known password can be supplied for when the MQI is running in Standalone Mode.
  • query_timeout(+Seconds) Sets the default time in seconds that a query is allowed to run before it is cancelled. This can be overridden on a query by query basis. If not set, the default is no timeout (-1).
  • pending_connections(+Count) Sets the number of pending connections allowed for the MQI as in tcp_listen/2. If not provided, the default is 5.
  • run_server_on_thread(+Run_Server_On_Thread) Determines whether mqi_start/1 runs in the background on its own thread or blocks until the MQI shuts down. Must be missing or set to true when running in "Embedded Mode" so that the SWI Prolog process can exit properly. If not set, the default is true.
  • server_thread(?Server_Thread) Specifies or retrieves the name of the thread the MQI will run on if run_server_on_thread(true). Passing in an atom for Server_Thread will only set the server thread name if run_server_on_thread(true). If Server_Thread is a variable, it is unified with a generated name.
  • write_connection_values(+Write_Connection_Values) Determines whether the server writes the port (or generated Unix Domain Socket) and password to STDOUT as it initializes. Used by language libraries to retrieve this information for connecting. If not set, the default is false.
  • write_output_to_file(+File) Redirects STDOUT and STDERR to the file path specified. Useful for debugging the MQI when it is being used in "Embedded Mode". If using multiple MQI instances in one SWI Prolog instance, only set this on the first one. Each time it is set the output will be redirected.
ClioPatria (version V3.1.1-42-gd6a756b-DIRTY)