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Updated: Thursday, June 13, 2019
 
 

info (1t)

Name

info - Return information about the state of the Tcl interpreter

Synopsis

info option ?arg arg ...?

Description

info(1t)                     Tcl Built-In Commands                    info(1t)



______________________________________________________________________________

NAME
       info - Return information about the state of the Tcl interpreter

SYNOPSIS
       info option ?arg arg ...?
______________________________________________________________________________

DESCRIPTION
       This  command  provides  information about various internals of the Tcl
       interpreter.  The legal options (which may be abbreviated) are:

       info args procname
              Returns a list containing the names of the arguments  to  proce-
              dure  procname,  in  order.   Procname must be the name of a Tcl
              command procedure.

       info body procname
              Returns the body of procedure procname.  Procname  must  be  the
              name of a Tcl command procedure.

       info class subcommand class ?arg ...
              Returns  information about the class, class. The subcommands are |
              described in CLASS INTROSPECTION below.

       info cmdcount
              Returns a count of the total number of commands that  have  been
              invoked in this interpreter.

       info commands ?pattern?
              If  pattern is not specified, returns a list of names of all the
              Tcl commands visible (i.e. executable without using a  qualified
              name) to the current namespace, including both the built-in com-
              mands written in C and the command procedures defined using  the
              proc  command.  If pattern is specified, only those names match-
              ing pattern are returned.  Matching is determined using the same
              rules as for string match.  pattern can be a qualified name like
              Foo::print*.  That is, it may  specify  a  particular  namespace
              using  a  sequence of namespace names separated by double colons
              (::), and may have pattern matching special  characters  at  the
              end  to specify a set of commands in that namespace.  If pattern
              is a qualified name, the resulting list  of  command  names  has
              each one qualified with the name of the specified namespace, and
              only the commands defined in the named namespace are returned.

       info complete command
              Returns 1 if command is a complete Tcl command in the  sense  of
              having  no  unclosed  quotes,  braces, brackets or array element
              names.  If the command does not appear to be complete then 0  is
              returned.  This command is typically used in line-oriented input
              environments to allow users to type in commands that span multi-
              ple lines;  if the command is not complete, the script can delay
              evaluating it until additional lines have been typed to complete
              the command.

       info coroutine
              Returns  the  name  of the currently executing coroutine, or the |
              empty string if either no coroutine is currently  executing,  or |
              the current coroutine has been deleted (but has not yet returned |
              or yielded since deletion).

       info default procname arg varname
              Procname must be the name of a Tcl  command  procedure  and  arg
              must  be the name of an argument to that procedure.  If arg does
              not have a default value then the command returns 0.   Otherwise
              it  returns  1 and places the default value of arg into variable
              varname.

       info errorstack ?interp?
              Returns, in a form that is programmatically easy to  parse,  the |
              function  names  and arguments at each level from the call stack |
              of the last error in the given interp, or in the current one  if |
              not specified.                                                   |

              This  form  is an even-sized list alternating tokens and parame- |
              ters. Tokens are currently either CALL, UP, or INNER, but  other |
              values  may be introduced in the future. CALL indicates a proce- |
              dure 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 allow to follow complex call paths, INNER homes in on the |
              offending  operation in the innermost procedure call, even going |
              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 tclsh.                                   |

       info exists varName
              Returns  1  if  the variable named varName exists in the current
              context (either as a global or  local  variable)  and  has  been
              defined by being given a value, returns 0 otherwise.

       info frame ?number?
              This  command  provides  access to all frames on the stack, even
              those hidden from info level. If number is not  specified,  this
              command  returns a number giving the frame level of the command.
              This is 1 if the command is invoked at top-level. If  number  is
              specified,  then the result is a dictionary containing the loca-
              tion information for the command at the numbered  level  on  the
              stack.

              If  number  is positive (> 0) then it selects a particular stack
              level (1 refers to the outer-most active command, 2 to the  com-
              mand  it  called, and so on, up to the current frame level which
              refers to info frame itself); otherwise it gives a  level  rela-
              tive  to  the  current command (0 refers to the current command,
              i.e., info frame itself, -1 to its caller, and so on).

              This is similar to how info level works, except that  this  sub-
              command   reports  all  frames,  like  sourced  scripts,  evals,
              uplevels, etc.

              Note that for nested commands, like "foo [bar  [x]]",  only  "x"
              will  be  seen by an info frame invoked within "x".  This is the
              same as for info level and error stack traces.

              The result dictionary may contain the keys  listed  below,  with
              the specified meanings for their values:

              type   This  entry is always present and describes the nature of
                     the location for the command. The recognized  values  are
                     source, proc, eval, and precompiled.

                     source
                            means that the command is found in a script loaded
                            by the source command.

                     proc
                            means that the command  is  found  in  dynamically
                            created procedure body.

                     eval
                            means  that  the  command  is  executed by eval or
                            uplevel.

                     precompiled
                            means that the command is found in a  pre-compiled
                            script  (loadable  by the package tbcload), and no
                            further information will be available.

              line   This entry provides the number of the line the command is
                     at inside of the script it is a part of. This information
                     is not present for type precompiled. For type source this
                     information  is  counted relative to the beginning of the
                     file, whereas for the last two types the line is  counted
                     relative to the start of the script.

              file   This  entry  is present only for type source. It provides
                     the normalized path of the file the command is in.

              cmd    This entry provides the string representation of the com-
                     mand. This is usually the unsubstituted form, however for
                     commands which are a canonically-constructed list  (e.g.,
                     as  produced  by the list command) executed by eval it is
                     the substituted form as they have no other string  repre-
                     sentation.  Care  is taken that the canonicality property
                     of the latter is not spoiled.

              proc   This entry is present only if the command is found in the
                     body  of  a  regular  Tcl procedure. It then provides the
                     name of that procedure.

              lambda This entry is present only if the command is found in the
                     body  of  an  anonymous  Tcl procedure, i.e. a lambda. It
                     then provides the entire  definition  of  the  lambda  in
                     question.

              level  This  entry  is  present  only if the queried frame has a
                     corresponding frame returned by info level.  It  provides
                     the index of this frame, relative to the current level (0
                     and negative numbers).

              A thing of note is that for  procedures  statically  defined  in
              files the locations of commands in their bodies will be reported
              with type source and absolute line  numbers,  and  not  as  type
              proc.  The  same  is  true  for  procedures nested in statically
              defined procedures, and literal eval scripts in files or  stati-
              cally defined procedures.

              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  usu-
              ally 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 possi-
              ble 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)

       info functions ?pattern?
              If pattern is not specified, returns a  list  of  all  the  math
              functions  currently  defined.   If  pattern  is specified, only
              those functions whose name matches pattern are returned.  Match-
              ing is determined using the same rules as for string match.

       info globals ?pattern?
              If  pattern is not specified, returns a list of all the names of
              currently-defined global variables.  Global variables are  vari-
              ables  in  the  global namespace.  If pattern is specified, only
              those names matching pattern are returned.  Matching  is  deter-
              mined using the same rules as for string match.

       info hostname
              Returns  the  name  of  the computer on which this invocation is
              being executed.  Note that 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.

       info level ?number?
              If number is not specified, this command returns a number giving
              the  stack  level of the invoking procedure, or 0 if the command
              is invoked at top-level.   If  number  is  specified,  then  the
              result  is  a  list consisting of the name and arguments for the
              procedure call at level number on the stack.  If number is posi-
              tive  then  it selects a particular stack level (1 refers to the
              top-most active procedure, 2 to the procedure it called, and  so
              on); otherwise it gives a level relative to the current level (0
              refers to the current procedure, -1 to its caller, and  so  on).
              See  the uplevel command for more information on what stack lev-
              els mean.

       info library
              Returns the name of the library directory in which standard  Tcl
              scripts   are  stored.   This  is  actually  the  value  of  the
              tcl_library variable and may be changed by setting tcl_library.

       info loaded ?interp?
              Returns a list describing all of the  packages  that  have  been
              loaded  into interp with the load command.  Each list element is
              a sub-list with two elements consisting of the name of the  file
              from  which  the package was loaded and the name of the package.
              For statically-loaded packages the file name will  be  an  empty
              string.   If  interp is omitted then information is returned for
              all packages loaded in any interpreter in the process.  To get a
              list of just the packages in the current interpreter, specify an
              empty string for the interp argument.

       info locals ?pattern?
              If pattern is not specified, returns a list of all the names  of
              currently-defined  local  variables,  including arguments to the
              current procedure, if any.  Variables defined with  the  global,
              upvar   and  variable commands will not be returned.  If pattern
              is specified, only those names matching  pattern  are  returned.
              Matching is determined using the same rules as for string match.

       info nameofexecutable
              Returns  the  full  path  name of the binary file from which the
              application was invoked.  If Tcl  was  unable  to  identify  the
              file, then an empty string is returned.

       info object subcommand object ?arg ...
              Returns  information  about  the object, object. The subcommands |
              are described in OBJECT INTROSPECTION below.

       info patchlevel
              Returns the value of the global variable  tcl_patchLevel,  which
              holds the exact version of the Tcl library by default.

       info procs ?pattern?
              If  pattern is not specified, returns a list of all the names of
              Tcl command procedures in the current namespace.  If pattern  is
              specified,  only  those procedure names in the current namespace
              matching pattern are returned.  Matching is determined using the
              same  rules as for string match.  If pattern contains any names-
              pace separators, they are used to select a namespace relative to
              the  current  namespace  (or relative to the global namespace if
              pattern starts with ::) to match within; the matching pattern is
              taken to be the part after the last namespace separator.

       info script ?filename?
              If a Tcl script file is currently being evaluated (i.e. there is
              a call to Tcl_EvalFile active or there is an  active  invocation
              of  the  source  command), then this command returns the name of
              the innermost file being processed.  If filename  is  specified,
              then  the  return value of this command will be modified for the
              duration of the active invocation to return that name.  This  is
              useful  in virtual file system applications.  Otherwise the com-
              mand returns an empty string.

       info sharedlibextension
              Returns the extension used on this platform  for  the  names  of
              files  containing  shared  libraries  (for  example,  .so  under
              Solaris).  If shared libraries are not supported on  this  plat-
              form then an empty string is returned.

       info tclversion
              Returns  the  value  of  the  global variable tcl_version, which
              holds the major and minor version of the Tcl library by default.

       info vars ?pattern?
              If pattern is not specified, returns a list of all the names  of
              currently-visible  variables.   This  includes  locals  and cur-
              rently-visible globals.  If pattern  is  specified,  only  those
              names  matching  pattern  are  returned.  Matching is determined
              using the same rules as for string  match.   pattern  can  be  a
              qualified  name  like  Foo::option*.   That is, it may specify a
              particular namespace using a sequence of namespace  names  sepa-
              rated  by double colons (::), and may have pattern matching spe-
              cial characters at the end to specify a set of variables in that
              namespace.   If  pattern is a qualified name, the resulting list
              of variable names has each matching namespace variable qualified
              with  the  name of its namespace.  Note that a currently-visible
              variable may not yet "exist" if it has  not  been  set  (e.g.  a
              variable declared but not set by variable).

   CLASS INTROSPECTION
       The following subcommand values are supported by info class:            |

       info class call class method
              Returns  a  description  of  the method implementations that are |
              used to provide a stereotypical instance of class's  implementa- |
              tion  of method (stereotypical instances being objects instanti- |
              ated 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, and unknown for  a  method |
              that is invoked as part of unknown method handling), a word giv- |
              ing 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 implemen- |
              tations  actually  use  next  to transfer control along the call |
              chain.                                                           |

       info class constructor class
              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.

       info class definition class method
              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  argu- |
              ments  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.

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

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

       info class forward class method
              This subcommand returns the argument list for  the  method  for- |
              warding called method that is set on the class called class.

       info class instances class ?pattern?
              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.

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

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

              -private
                     If  the  -private flag is given, the list of methods will |
                     also include the private (i.e. non-exported)  methods  of |
                     the  class  (and superclasses and mixins, if -all is also |
                     given).                                                   |

       info class methodtype class method
              This subcommand returns a description of the type of implementa- |
              tion  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.

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

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

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

       info class variables class
              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).     |

   OBJECT INTROSPECTION                                                        |
       The following subcommand values are supported by info object:

       info object call object method
              Returns  a  description  of  the method implementations that are |
              used to provide object's implementation of  method.   This  con- |
              sists  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, fil- |
              ter for an applied filter, 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  quali- |
              fied  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 implemen- |
              tations actually use next to transfer  control  along  the  call |
              chain.                                                           |

       info object class object ?className?
              If  className  is  unspecified, 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.

       info object definition object method
              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 ele- |
              ment is the body of the method.

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

       info object forward object method
              This subcommand returns the argument list for  the  method  for- |
              warding called method that is set on the object called object.

       info object isa category object ?arg?
              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 sup- |
              ported categories are:

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

              info object isa metaclass object
                     This  returns whether object is a class that can manufac- |
                     ture classes (i.e. is oo::class or a subclass of it).

              info object isa mixin object class
                     This returns whether class is directly mixed into object. |

              info object isa object object
                     This returns whether object really is an object.          |

              info object isa typeof object class
                     This returns whether class is the type  of  object  (i.e. |
                     whether object is an instance of class or one of its sub- |
                     classes, whether direct or indirect).                     |

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

              -all   If  the  -all  flag  is  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 super- |
                     classes of those classes.

              -private
                     If the -private flag is given, the list of  methods  will |
                     also  include  the private (i.e. non-exported) methods of |
                     the object (and classes, if -all is also given).          |

       info object methodtype object method
              This subcommand returns a description of the type of implementa- |
              tion 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.

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

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

       info object variables object
              This subcommand returns a list of all variables that  have  been |
              declared  for  the  object named object (i.e. that are automati- |
              cally present in the object's methods).

       info object vars object ?pattern?
              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 cur- |
              rently 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 illus- |
       trates 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  imple- |
       mented  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]                  |
              }                                                                |


ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:


       +---------------+------------------+
       |ATTRIBUTE TYPE | ATTRIBUTE VALUE  |
       +---------------+------------------+
       |Availability   | runtime/tcl-8    |
       +---------------+------------------+
       |Stability      | Uncommitted      |
       +---------------+------------------+
SEE ALSO
       global(n),   oo::class(n),   oo::define(n),   oo::object(n),   proc(n), |
       self(n), tcl_library(n), tcl_patchLevel(n), tcl_version(n)

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



NOTES
       This    software    was    built    from    source     available     at
       https://github.com/oracle/solaris-userland.    The  original  community
       source was downloaded from  http://prdownloads.sourceforge.net/tcl/tcl-
       core8.6.7-src.tar.gz

       Further information about this software can be found on the open source
       community website at https://www.tcl.tk/.



Tcl                                   8.4                             info(1t)