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info(3tcl) Tcl Built-In Commands info(3tcl) 





NAME


info - Information about the state of the Tcl interpreter






SYNOPSIS


info option ?arg arg ...?








DESCRIPTION


Available commands:



  

  
Returns the names of the parameters to the procedure named
      procname.

  

  
Returns the body of the procedure named procname.

  

  
Returns information about the class named class. See CLASS
      INTROSPECTION below.

  

  
Returns the total number of commands evaluated in this interpreter.

  

  
Returns a the type of the command named commandName. Built-in types
      are:







  

  
commandName was created by interp alias. In a safe
      interpreter an alias is only visible if both the alias and the target are
      visible.

  

  
commandName was created by coroutine.

  

  
commandName was created by namespace ensemble.

  

  
commandName was created by namespace import.

  

  
commandName was created by the Tcl_CreateObjCommand
      interface directly without further registration of the type of
    command.

  

  
commandName is the public command that represents an instance of
      oo::object or one of its subclasses.

  

  
commandName is the private command, my by default, that
      represents an instance of oo::object or one of its subclasses.

  

  
commandName was created by proc.

  

  
commandName was created by interp create.

  

  
commandName was created by zlib stream.







  

  
Returns the names of all commands visible in the current namespace. If
      pattern is given, returns only those names that match according to
      string match. Only the last component of pattern is a
      pattern. Other components identify a namespace. See NAMESPACE
      RESOLUTION in the namespace(3tcl) documentation.

  

  
Returns 1 if command is a complete command, and 0 otherwise.
      Typically used in line-oriented input environments to allow users to type
      in commands that span multiple lines.

  

  
Returns 1 if varName is a constant variable (see const) and
      0 otherwise.

  

  
Returns the list of constant variables (see const) in the current
      scope, or the list of constant variables matching pattern (if that
      is provided) in a manner similar to info vars.

  

  
Returns the name of the current coroutine, or the empty string if
      there is no current coroutine or the current coroutine has been
    deleted.

  

  
If the parameter parameter for the procedure named procname
      has a default value, stores that value in varname and returns
      1. Otherwise, returns 0.

  

  
Returns a description of the active command at each level for the last
      error in the current interpreter, or in the interpreter named
      interp if given.






The description is a dictionary of tokens and parameters. Tokens
    are currently either CALL, UP, or INNER, but other
    values may be introduced in the future. CALL indicates a command
    call, and its parameter is the corresponding info level 0.
    UP indicates a shift in variable frames generated by uplevel
    or similar, and applies to the previous CALL item. Its parameter is
    the level offset. INNER identifies the “inner context”,
    which is the innermost atomic command or bytecode instruction that raised
    the error, along with its arguments when available. While CALL and
    UP provide a trail of the call path, INNER provides details of
    the offending operation in the innermost procedure call, even to
    sub-expression granularity.


This information is also present in the -errorstack entry
    of the options dictionary returned by 3-argument catch; info
    errorstack is a convenient way of retrieving it for uncaught errors at
    top-level in an interactive interpreter.





  

  
Returns 1 if a variable named varName is visible and has
      been defined, and 0 otherwise.

  

  
Returns the depth of the call to info frame itself. Otherwise,
      returns a dictionary describing the active command at the depth,
      which counts all commands visible to info level, plus commands that
      don't create a new level, such as eval, source, or
      uplevel. The frame depth is always greater than the current
    level.






If depth is greater than 0 it is the frame at that
    depth. Otherwise it is the number of frames up from the current frame.


As with info level and error traces, for nested commands
    like “foo [bar [x]]”, only “x” is seen by
    info frame invoked within “x”.


The dictionary may contain the following keys:



  

  
Always present. Possible values are source, proc,
      eval, and precompiled.







  

  
A script loaded via the source command.

  

  
The body of a procedure that could not be traced back to a line in a
      particular script.

  

  
The body of a script provided to eval or uplevel.

  

  
A precompiled script (loadable by the package tbcload), and no
      further information is available.







  

  
The line number of of the command inside its script. Not available for
      precompiled commands. When the type is source, the line
      number is relative to the beginning of the file, whereas for the last two
      types it is relative to the start of the script.

  

  
For type source, provides the normalized path of the file that
      contains the command.

  

  
The command before substitutions were performed.

  

  
For type prod, the name of the procedure containing the
    command.

  

  
For a command in a script evaluated as the body of an unnamed routine via
      the apply command, the definition of that routine.

  

  
For a frame that corresponds to a level, (to be determined).




When a command can be traced to its literal definition in some
    script, e.g. procedures nested in statically defined procedures, and literal
    eval scripts in files or statically defined procedures, its type is
    source and its location is the absolute line number in the script.
    Otherwise, its type is proc and its location is its line number
    within the body of the procedure.


In contrast, procedure definitions and eval within a
    dynamically evaluated environment count line numbers relative to the
    start of their script, even if they would be able to count relative to the
    start of the outer dynamic script. That type of number usually makes more
    sense.


A different way of describing this behaviour is that file-based
    locations are tracked as deeply as possible, and where this is not possible
    the lines are counted based on the smallest possible eval or
    procedure body, as that scope is usually easier to find than any dynamic
    outer scope.


The syntactic form {*} is handled like eval. I.e. if
    it is given a literal list argument the system tracks the line number within
    the list words as well, and otherwise all line numbers are counted relative
    to the start of each word (smallest scope)





  

  
If pattern is not given, returns a list of all the math functions
      currently defined. If pattern is given, returns only those names
      that match pattern according to string match.

  

  
If pattern is not given, returns a list of all the names of
      currently-defined global variables. Global variables are variables in the
      global namespace. If pattern is given, only those names matching
      pattern are returned. Matching is determined using the same rules
      as for string match.

  

  
Returns the name of the current host.






This name is not guaranteed to be the fully-qualified domain name
    of the host. Where machines have several different names, as is common on
    systems with both TCP/IP (DNS) and NetBIOS-based networking installed, it is
    the name that is suitable for TCP/IP networking that is returned.





  

  
If number is not given, the level this routine was called from.
      Otherwise returns the complete command active at the given level. If
      number is greater than 0, it is the desired level.
      Otherwise, it is number levels up from the current level. A
      complete command is the words in the command, with all substitutions
      performed, meaning that it is a list. See uplevel for more
      information on levels.

  

  
Returns the value of tcl_library, which is the name of the library
      directory in which the scripts distributed with Tcl scripts are
    stored.

  

  
Returns the name of each file loaded in interp by the load
      command with prefix prefix . If prefix is not given, returns
      a list where each item is the name of the loaded file and the prefix for
      which the file was loaded. For a statically-loaded package the name of the
      file is the empty string. For interp, the empty string is the
      current interpreter.

  

  
If pattern is given, returns the name of each local variable
      matching pattern according to string match. Otherwise,
      returns the name of each local variable. A variables defined with the
      global, upvar or variable is not local.

  

  
Returns the absolute pathname of the program for the current interpreter.
      If such a file can not be identified an empty string is returned.

  

  
Returns information about the object named object.
      subcommand is described OBJECT INTROSPECTION below.

  

  
Returns the value of the global variable tcl_patchLevel, in which
      the exact version of the Tcl library initially stored.

  

  
Returns the names of all visible procedures. If pattern is given,
      returns only those names that match according to string match. Only
      the final component in pattern is actually considered a pattern.
      Any qualifying components simply select a namespace. See NAMESPACE
      RESOLUTION in the namespace(3tcl) documentation.

  

  
Returns the pathname of the innermost script currently being evaluated, or
      the empty string if no pathname can be determined. If filename is
      given, sets the return value of any future calls to info script for
      the duration of the innermost active script. This is useful in virtual
      file system applications.

  

  
Returns the extension used on this platform for names of shared libraries,
      e.g. .so under Solaris. Returns the empty string if shared
      libraries are not supported on this platform.

  

  
Returns the value of the global variable tcl_version, in which the
      major and minor version of the Tcl library are stored.

  

  
If pattern is not given, returns the names of all visible
      variables. If pattern is given, returns only those names that match
      according to string match. Only the last component of
      pattern is a pattern. Other components identify a namespace. See
      NAMESPACE RESOLUTION in the namespace(3tcl) documentation.
      When pattern is a qualified name, results are fully qualified.






A variable that has been declared but not yet given a value will
    be included in the results.






CLASS INTROSPECTION


The following subcommand values are supported by info
    class:



  

  
Returns a description of the method implementations that are used to
      provide a stereotypical instance of class's implementation of
      method (stereotypical instances being objects instantiated by a
      class without having any object-specific definitions added). This consists
      of a list of lists of four elements, where each sublist consists of a word
      that describes the general type of method implementation (being one of
      method for an ordinary method, filter for an applied filter,
      private for a private method, and unknown for a method that
      is invoked as part of unknown method handling), a word giving the name of
      the particular method invoked (which is always the same as method
      for the method type, and “unknown” for the
      unknown type), a word giving the fully qualified name of the class
      that defined the method, and a word describing the type of method
      implementation (see info class methodtype).






Note that there is no inspection of whether the method
    implementations actually use next to transfer control along the call
    chain, and the call chains that this command files do not actually contain
    private methods.





  

  
This subcommand returns a description of the definition of the constructor
      of class class. The definition is described as a two element list;
      the first element is the list of arguments to the constructor in a form
      suitable for passing to another call to proc or a method
      definition, and the second element is the body of the constructor. If no
      constructor is present, this returns the empty list.

  

  
This subcommand returns a description of the definition of the method
      named method of class class. The definition is described as
      a two element list; the first element is the list of arguments to the
      method in a form suitable for passing to another call to proc or a
      method definition, and the second element is the body of the method.

  

  
This subcommand returns the definition namespace for kind
      definitions of the class class; the definition namespace only
      affects the instances of class, not class itself. The
      kind can be either -class to return the definition namespace
      used for oo::define, or -instance to return the definition
      namespace used for oo::objdefine; the -class kind is default
      (though this is only actually useful on classes that are subclasses of
      oo::class).






If class does not provide a definition namespace of the
    given kind, this command returns the empty string. In those circumstances,
    the oo::define and oo::objdefine commands look up which
    definition namespace to use using the class inheritance hierarchy.





  

  
This subcommand returns the body of the destructor of class class.
      If no destructor is present, this returns the empty string.

  

  
This subcommand returns the list of filter methods set on the class.

  

  
This subcommand returns the argument list for the method forwarding called
      method that is set on the class called class.

  

  
This subcommand returns a list of instances of class class. If the
      optional pattern argument is present, it constrains the list of
      returned instances to those that match it according to the rules of
      string match.

  

  
This subcommand returns a list of all public (i.e. exported) methods of
      the class called class. Any of the following options may be
      given, controlling exactly which method names are returned:







  

  
If the -all flag is given, and the -scope flag is not given,
      the list of methods will include those methods defined not just by the
      class, but also by the class's superclasses and mixins.

  

  
If the -private flag is given, and the -scope flag is not
      given, the list of methods will also include the non-exported methods of
      the class (and superclasses and mixins, if -all is also given).
      Note that this naming is an unfortunate clash with true private methods;
      this option name is retained for backward compatibility.

  

  
Returns a list of all methods on class that have the given
      visibility scope. When this option is supplied, both the
      -all and -private options are ignored. The valid values for
      scope are:







  

  
Only methods with public scope (i.e., callable from anywhere by any
      instance of this class) are to be returned.

  

  
Only methods with unexported scope (i.e., only callable via
      my) are to be returned.

  

  
Only methods with private scope (i.e., only callable from within
      this class's methods) are to be returned.









  

  
This subcommand returns a description of the type of implementation used
      for the method named method of class class. When the result
      is method, further information can be discovered with info
      class definition, and when the result is forward,
      further information can be discovered with info class forward.

  

  
This subcommand returns a list of all classes that have been mixed into
      the class named class.

  

  
This subcommand returns a sorted list of properties defined on the class
      named class. The options define exactly which properties are
      returned:







  

  
With this option, the properties from the superclasses and mixins of the
      class are also returned.

  

  
This option (the default behavior) asks for the readable properties to be
      returned. Only readable or writable properties are returned, not
    both.

  

  
This option asks for the writable properties to be returned. Only readable
      or writable properties are returned, not both.







  

  
This subcommand returns a list of direct subclasses of class class.
      If the optional pattern argument is present, it constrains the list
      of returned classes to those that match it according to the rules of
      string match.

  

  
This subcommand returns a list of direct superclasses of class
      class in inheritance precedence order.

  

  
This subcommand returns a list of all variables that have been declared
      for the class named class (i.e. that are automatically present in
      the class's methods, constructor and destructor). If the -private
      option is given, this lists the private variables declared instead.








OBJECT INTROSPECTION


The following subcommand values are supported by info
    object:



  

  
Returns a description of the method implementations that are used to
      provide object's implementation of method. This consists of
      a list of lists of four elements, where each sublist consists of a word
      that describes the general type of method implementation (being one of
      method for an ordinary method, filter for an applied filter,
      private for a private method, and unknown for a method that
      is invoked as part of unknown method handling), a word giving the name of
      the particular method invoked (which is always the same as method
      for the method type, and “unknown” for the
      unknown type), a word giving what defined the method (the fully
      qualified name of the class, or the literal string object if the
      method implementation is on an instance), and a word describing the type
      of method implementation (see info object methodtype).






Note that there is no inspection of whether the method
    implementations actually use next to transfer control along the call
    chain, and the call chains that this command files do not actually contain
    private methods.





  

  
If className is not given, this subcommand returns class of the
      object object. If className is present, this subcommand
      returns a boolean value indicating whether the object is of that
      class.

  

  
Returns the unique creation identifier for the object object. This
      creation identifier is unique to the object (within a Tcl interpreter) and
      cannot be controlled at object creation time or altered afterwards.






Implementation note: the creation identifier is used to
    generate unique identifiers associated with the object, especially for
    private variables.





  

  
This subcommand returns a description of the definition of the method
      named method of object object. The definition is described
      as a two element list; the first element is the list of arguments to the
      method in a form suitable for passing to another call to proc or a
      method definition, and the second element is the body of the method.

  

  
This subcommand returns the list of filter methods set on the object.

  

  
This subcommand returns the argument list for the method forwarding called
      method that is set on the object called object.

  

  
This subcommand tests whether an object belongs to a particular category,
      returning a boolean value that indicates whether the object
      argument meets the criteria for the category. The supported categories
      are:







  

  
This returns whether object is a class (i.e. an instance of
      oo::class or one of its subclasses).

  

  
This returns whether object is a class that can manufacture classes
      (i.e. is oo::class or a subclass of it).

  

  
This returns whether class is directly mixed into
    object.

  

  
This returns whether object really is an object.

  

  
This returns whether class is the type of object (i.e.
      whether object is an instance of class or one of its
      subclasses, whether direct or indirect).







  

  
This subcommand returns a list of all public (i.e. exported) methods of
      the object called object. Any of the following options may
      be given, controlling exactly which method names are returned:







  

  
If the -all flag is given, and the -scope flag is not given,
      the list of methods will include those methods defined not just by the
      object, but also by the object's class and mixins, plus the superclasses
      of those classes.

  

  
If the -private flag is given, and the -scope flag is not
      given, the list of methods will also include the non-exported methods of
      the object (and classes, if -all is also given). Note that this
      naming is an unfortunate clash with true private methods; this option name
      is retained for backward compatibility.

  

  
Returns a list of all methods on object that have the given
      visibility scope. When this option is supplied, both the
      -all and -private options are ignored. The valid values for
      scope are:







  

  
Only methods with public scope (i.e., callable from anywhere) are
      to be returned.

  

  
Only methods with unexported scope (i.e., only callable via
      my) are to be returned.

  

  
Only methods with private scope (i.e., only callable from within
      this object's instance methods) are to be returned.









  

  
This subcommand returns a description of the type of implementation used
      for the method named method of object object. When the
      result is method, further information can be discovered with
      info object definition, and when the result is
      forward, further information can be discovered with info object
      forward.

  

  
This subcommand returns a list of all classes that have been mixed into
      the object named object.

  

  
This subcommand returns the name of the internal namespace of the object
      named object.

  

  
This subcommand returns a sorted list of properties defined on the object
      named object. The options define exactly which properties
      are returned:







  

  
With this option, the properties from the class, superclasses and mixins
      of the object are also returned.

  

  
This option (the default behavior) asks for the readable properties to be
      returned. Only readable or writable properties are returned, not
    both.

  

  
This option asks for the writable properties to be returned. Only readable
      or writable properties are returned, not both.







  

  
This subcommand returns a list of all variables that have been declared
      for the object named object (i.e. that are automatically present in
      the object's methods). If the -private option is given, this lists
      the private variables declared instead.

  

  
This subcommand returns a list of all variables in the private namespace
      of the object named object. If the optional pattern argument
      is given, it is a filter (in the syntax of a string match glob
      pattern) that constrains the list of variables returned. Note that this is
      different from the list returned by info object variables; that can
      include variables that are currently unset, whereas this can include
      variables that are not automatically included by any of object's
      methods (or those of its class, superclasses or mixins).










EXAMPLES


This command prints out a procedure suitable for saving in a Tcl
    script:






proc printProc {procName} {


    set result [list proc $procName]


    set formals {}


    foreach var [info args $procName] {


        if {[info default $procName $var def]} {


            lappend formals [list $var $def]


        } else {


            # Still need the list-quoting because variable


            # names may properly contain spaces.


            lappend formals [list $var]


        }


    }


    puts [lappend result $formals [info body $procName]]
}






EXAMPLES WITH OBJECTS


Every object necessarily knows what its class is; this information
    is trivially extractable through introspection:






oo::class create c
c create o
puts [info object class o]


                     → prints "::c"
puts [info object class c]


                     → prints "::oo::class"




The introspection capabilities can be used to discover what class
    implements a method and get how it is defined. This procedure illustrates
    how:






proc getDef {obj method} {


    foreach inf [info object call $obj $method] {


        lassign $inf calltype name locus methodtype


        # Assume no forwards or filters, and hence no $calltype


        # or $methodtype checks...


        if {$locus eq "object"} {


            return [info object definition $obj $name]


        } else {


            return [info class definition $locus $name]


        }


    }


    error "no definition for $method"
}




This is an alternate way of looking up the definition; it is
    implemented by manually scanning the list of methods up the inheritance
    tree. This code assumes that only single inheritance is in use, and that
    there is no complex use of mixed-in classes (in such cases, using info
    object call as above is the simplest way of doing this by far):






proc getDef {obj method} {


    if {$method in [info object methods $obj]} {


        # Assume no forwards


        return [info object definition $obj $method]


    }


    set cls [info object class $obj]


    while {$method ni [info class methods $cls]} {


        # Assume the simple case


        set cls [lindex [info class superclass $cls] 0]


        if {$cls eq ""} {


            error "no definition for $method"


        }


    }


    # Assume no forwards


    return [info class definition $cls $method]
}










SEE ALSO


global(3tcl), oo::class(3tcl), oo::define(3tcl), oo::object(3tcl),
    proc(3tcl), self(3tcl), tcl_library(3tcl), tcl_patchLevel(3tcl),
    tcl_version(3tcl)






KEYWORDS


command, information, interpreter, introspection, level,
    namespace, object, procedure, variable







  

    8.4
    Tcl