path: root/doc/info.n

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'\" Copyright (c) 1993 The Regents of the University of California.
'\" Copyright (c) 1994-1997 Sun Microsystems, Inc.
'\" Copyright (c) 1993-1997 Bell Labs Innovations for Lucent Technologies
'\" Copyright (c) 1998-2000 Ajuba Solutions
'\" Copyright (c) 2007-2008 Donal K. Fellows
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'\" RCS: @(#) $Id: info.n,v 1.28 2008/09/23 05:05:47 dkf Exp $
'\" 
.so man.macros
.TH info n 8.4 Tcl "Tcl Built-In Commands"
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
info \- Return information about the state of the Tcl interpreter
.SH SYNOPSIS
\fBinfo \fIoption \fR?\fIarg arg ...\fR?
.BE
.SH DESCRIPTION
.PP
This command provides information about various internals of the Tcl
interpreter.
The legal \fIoption\fRs (which may be abbreviated) are:
.TP
\fBinfo args \fIprocname\fR
.
Returns a list containing the names of the arguments to procedure
\fIprocname\fR, in order.  \fIProcname\fR must be the name of a
Tcl command procedure.
.TP
\fBinfo body \fIprocname\fR
.
Returns the body of procedure \fIprocname\fR.  \fIProcname\fR must be
the name of a Tcl command procedure.
.TP
\fBinfo class\fI subcommand class\fR ?\fIarg ...\fR
.VS 8.6
Returns information about the class, \fIclass\fR. The \fIsubcommand\fRs are
described in \fBCLASS INTROSPECTION\fR below.
.VE 8.6
.TP
\fBinfo cmdcount\fR
.
Returns a count of the total number of commands that have been invoked
in this interpreter.
.TP
\fBinfo commands \fR?\fIpattern\fR?
.
If \fIpattern\fR 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 commands written in C and
the command procedures defined using the \fBproc\fR command.
If \fIpattern\fR is specified,
only those names matching \fIpattern\fR are returned.
Matching is determined using the same rules as for \fBstring match\fR.
\fIpattern\fR can be a qualified name like \fBFoo::print*\fR.
That is, it may specify a particular namespace
using a sequence of namespace names separated by double colons (\fB::\fR),
and may have pattern matching special characters
at the end to specify a set of commands in that namespace.
If \fIpattern\fR 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.
.\" Technically, most of this hasn't changed; that's mostly just the
.\" way it always worked. Hardly anyone knew that though.
.TP
\fBinfo complete \fIcommand\fR
.
Returns 1 if \fIcommand\fR 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 multiple lines;  if the
command is not complete, the script can delay evaluating it until additional
lines have been typed to complete the command.
.TP
\fBinfo default \fIprocname arg varname\fR
.
\fIProcname\fR must be the name of a Tcl command procedure and \fIarg\fR
must be the name of an argument to that procedure.  If \fIarg\fR
does not have a default value then the command returns \fB0\fR.
Otherwise it returns \fB1\fR and places the default value of \fIarg\fR
into variable \fIvarname\fR.
.TP
\fBinfo exists \fIvarName\fR
.
Returns \fB1\fR if the variable named \fIvarName\fR exists in the
current context (either as a global or local variable) and has been
defined by being given a value, returns \fB0\fR otherwise.
.TP
\fBinfo frame\fR ?\fInumber\fR?
.
This command provides access to all frames on the stack, even those
hidden from \fBinfo level\fR. If \fInumber\fR 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 \fInumber\fR is
specified, then the result is a dictionary containing the location
information for the command at the \fInumber\fRed level on the stack.
.RS
.PP
If \fInumber\fR is positive (> 0) then it selects a particular stack
level (1 refers to the top-most active command, i.e., \fBinfo frame\fR
itself, 2 to the command it was called from, and so on); otherwise it
gives a level relative to the current command (0 refers to the current
command, i.e., \fBinfo frame\fR itself, -1 to its caller, and so on).
.PP
This is similar to how \fBinfo level\fR works, except that this
subcommand reports all frames, like \fBsource\fRd scripts,
\fBeval\fRs, \fBuplevel\fRs, etc.
.PP
Note that for nested commands, like
.QW "foo [bar [x]]" ,
only
.QW x
will be seen by an \fBinfo frame\fR invoked within
.QW x .
This is the same as for \fBinfo level\fR and error stack traces.
.PP
The result dictionary may contain the keys listed below, with the
specified meanings for their values:
.TP
\fBtype\fR
.
This entry is always present and describes the nature of the location
for the command. The recognized values are \fBsource\fR, \fBproc\fR,
\fBeval\fR, and \fBprecompiled\fR.
.RS
.TP
\fBsource\fR\0\0\0\0\0\0\0\0
.
means that the command is found in a script loaded by the \fBsource\fR
command.
.TP
\fBproc\fR\0\0\0\0\0\0\0\0
.
means that the command is found in dynamically created procedure body.
.TP
\fBeval\fR\0\0\0\0\0\0\0\0
.
means that the command is executed by \fBeval\fR or \fBuplevel\fR.
.TP
\fBprecompiled\fR\0\0\0\0\0\0\0\0
.
means that the command is found in a precompiled script (loadable by
the package \fBtbcload\fR), and no further information will be
available.
.RE
.TP
\fBline\fR
.
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
\fBprecompiled\fR. For type \fBsource\fR 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.
.TP
\fBfile\fR
.
This entry is present only for type \fBsource\fR. It provides the
normalized path of the file the command is in.
.TP
\fBcmd\fR
.
This entry provides the string representation of the command. This is
usually the unsubstituted form, however for commands which are a pure
list executed by eval it is the substituted form as they have no other
string representation. Care is taken that the pure-List property of
the latter is not spoiled.
.TP
\fBproc\fR
.
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.
.TP
\fBlambda\fR
.
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.
.TP
\fBlevel\fR
.
This entry is present only if the queried frame has a corresponding
frame returned by \fBinfo level\fR. It provides the index of this
frame, relative to the current level (0 and negative numbers).
.PP
A thing of note is that for procedures statically defined in files the
locations of commands in their bodies will be reported with type
\fBsource\fR and absolute line numbers, and not as type
\fBproc\fR. The same is true for procedures nested in statically
defined procedures, and literal eval scripts in files or statically
defined procedures.
.PP
In contrast, a procedure definition or \fBeval\fR within a dynamically
\fBeval\fRuated environment count linenumbers 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.
.PP
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
\fBeval\fR or procedure body, as that scope is usually easier to find
than any dynamic outer scope.
.PP
The syntactic form \fB{*}\fR is handled like \fBeval\fR. I.e. if it
is given a literal list argument the system tracks the linenumber
within the list words as well, and otherwise all linenumbers are
counted relative to the start of each word (smallest scope)
.RE
.TP
\fBinfo functions \fR?\fIpattern\fR?
.
If \fIpattern\fR is not specified, returns a list of all the math
functions currently defined.
If \fIpattern\fR is specified, only those functions whose name matches
\fIpattern\fR are returned.  Matching is determined using the same
rules as for \fBstring match\fR.
.TP
\fBinfo globals \fR?\fIpattern\fR?
.
If \fIpattern\fR is not specified, returns a list of all the names
of currently-defined global variables.
Global variables are variables in the global namespace.
If \fIpattern\fR is specified, only those names matching \fIpattern\fR
are returned.  Matching is determined using the same rules as for
\fBstring match\fR.
.TP
\fBinfo hostname\fR
.
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.
.TP
\fBinfo level\fR ?\fInumber\fR?
.
If \fInumber\fR 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 \fInumber\fR is specified,
then the result is a list consisting of the name and arguments for the
procedure call at level \fInumber\fR on the stack.  If \fInumber\fR
is positive 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 \fBuplevel\fR command for more information on what stack
levels mean.
.TP
\fBinfo library\fR
.
Returns the name of the library directory in which standard Tcl
scripts are stored.
This is actually the value of the \fBtcl_library\fR
variable and may be changed by setting \fBtcl_library\fR.
See the \fBtclvars\fR manual entry for more information.
.TP
\fBinfo loaded \fR?\fIinterp\fR?
.
Returns a list describing all of the packages that have been loaded into
\fIinterp\fR with the \fBload\fR 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 \fIinterp\fR 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 \fIinterp\fR argument.
.TP
\fBinfo locals \fR?\fIpattern\fR?
.
If \fIpattern\fR 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 \fBglobal\fR, \fBupvar\fR  and
\fBvariable\fR commands will not be returned.
If \fIpattern\fR is specified, only those names matching \fIpattern\fR
are returned.  Matching is determined using the same rules as for
\fBstring match\fR.
.TP
\fBinfo nameofexecutable\fR
.
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.
.TP
\fBinfo object\fI subcommand object\fR ?\fIarg ...\fR
.VS 8.6
Returns information about the object, \fIobject\fR. The \fIsubcommand\fRs are
described in \fBOBJECT INTROSPECTION\fR below.
.VE 8.6
.TP
\fBinfo patchlevel\fR
.
Returns the value of the global variable \fBtcl_patchLevel\fR; see
the \fBtclvars\fR manual entry for more information.
.TP
\fBinfo procs \fR?\fIpattern\fR?
.
If \fIpattern\fR is not specified, returns a list of all the
names of Tcl command procedures in the current namespace.
If \fIpattern\fR is specified,
only those procedure names in the current namespace
matching \fIpattern\fR are returned.
Matching is determined using the same rules as for
\fBstring match\fR.
If \fIpattern\fR contains any namespace separators, they are used to
select a namespace relative to the current namespace (or relative to
the global namespace if \fIpattern\fR starts with \fB::\fR) to match
within; the matching pattern is taken to be the part after the last
namespace separator.
.TP
\fBinfo script\fR ?\fIfilename\fR?
.
If a Tcl script file is currently being evaluated (i.e. there is a
call to \fBTcl_EvalFile\fR active or there is an active invocation
of the \fBsource\fR command), then this command returns the name
of the innermost file being processed.  If \fIfilename\fR 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 command returns an empty string.
.TP
\fBinfo sharedlibextension\fR
.
Returns the extension used on this platform for the names of files
containing shared libraries (for example, \fB.so\fR under Solaris).
If shared libraries are not supported on this platform then an empty
string is returned.
.TP
\fBinfo tclversion\fR
.
Returns the value of the global variable \fBtcl_version\fR; see
the \fBtclvars\fR manual entry for more information.
.TP
\fBinfo vars\fR ?\fIpattern\fR?
.
If \fIpattern\fR is not specified,
returns a list of all the names of currently-visible variables.
This includes locals and currently-visible globals.
If \fIpattern\fR is specified, only those names matching \fIpattern\fR
are returned.  Matching is determined using the same rules as for
\fBstring match\fR.
\fIpattern\fR can be a qualified name like \fBFoo::option*\fR.
That is, it may specify a particular namespace
using a sequence of namespace names separated by double colons (\fB::\fR),
and may have pattern matching special characters
at the end to specify a set of variables in that namespace.
If \fIpattern\fR 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
.QW exist
if it has not
been set (e.g. a variable declared but not set by \fBvariable\fR).
.SS "CLASS INTROSPECTION"
.VS 8.6
.PP
The following \fIsubcommand\fR values are supported by \fBinfo class\fR:
.VE 8.6
.TP
\fBinfo class constructor\fI class\fR
.VS 8.6
This subcommand returns a description of the definition of the constructor of
class \fIclass\fR. The defintion 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 \fBproc\fR or a method defintion, and the second
element is the body of the constructor. If no constructor is present, this
returns the empty list.
.VE 8.6
.TP
\fBinfo class definition\fI class method\fR
.VS 8.6
This subcommand returns a description of the definition of the method named
\fImethod\fR of class \fIclass\fR. The defintion 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 \fBproc\fR or a method defintion, and
the second element is the body of the method.
.VE 8.6
.TP
\fBinfo class destructor\fI class\fR
.VS 8.6
This subcommand returns the body of the destructor of class \fIclass\fR. If no
destructor is present, this returns the empty string.
.VE 8.6
.TP
\fBinfo class filters\fI class\fR
.VS 8.6
This subcommand returns the list of filter methods set on the class.
.VE 8.6
.TP
\fBinfo class forward\fI class method\fR
.VS 8.6
This subcommand returns the argument list for the method forwarding called
\fImethod\fR that is set on the class called \fIclass\fR.
.VE 8.6
.TP
\fBinfo class instances\fI class\fR ?\fIpattern\fR?
.VS 8.6
This subcommand returns a list of instances of class \fIclass\fR. If the
optional \fIpattern\fR argument is present, it constrains the list of returned
instances to those that match it according to the rules of \fBstring match\fR.
.VE 8.6
.TP
\fBinfo class methods\fI class\fR ?\fIoptions...\fR?
.VS 8.6
This subcommand returns a list of all public (i.e. exported) methods of the
class called \fIclass\fR. Any of the following \fIoption\fRs may be
specified, controlling exactly which method names are returned:
.RS
.VE 8.6
.TP
\fB\-all\fR
.VS 8.6
If the \fB\-all\fR 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.
.VE 8.6
.TP
\fB\-private\fR
.VS 8.6
If the \fB\-private\fR 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 \fB\-all\fR is also given).
.RE
.VE 8.6
.TP
\fBinfo class mixins\fI class\fR
.VS 8.6
This subcommand returns a list of all classes that have been mixed into the
class named \fIclass\fR.
.VE 8.6
.TP
\fBinfo class subclasses\fI class\fR ?\fIpattern\fR?
.VS 8.6
This subcommand returns a list of direct subclasses of class \fIclass\fR. If
the optional \fIpattern\fR argument is present, it constrains the list of
returned classes to those that match it according to the rules of \fBstring
match\fR.
.VE 8.6
.TP
\fBinfo class superclasses\fI class\fR
.VS 8.6
This subcommand returns a list of direct superclasses of class \fIclass\fR in
inheritance precedence order.
.VE 8.6
.TP
\fBinfo class variables\fI class\fR
.VS 8.6
This subcommand returns a list of all variables that have been declared for
the class named \Iclass\fR (i.e. that are automatically present in the
class's methods, constructor and destructor).
.SS "OBJECT INTROSPECTION"
.PP
The following \fIsubcommand\fR values are supported by \fBinfo object\fR:
.VE 8.6
.TP
\fBinfo object class\fI object\fR ?\fIclassName\fR?
.VS 8.6
If \fIclassName\fR is unspecified, this subcommand returns class of the
\fIobject\fR object. If \fIclassName\fR is present, this subcommand returns a
boolean value indicating whether the \fIobject\fR is of that class.
.VE 8.6
.TP
\fBinfo object definition\fI object method\fR
.VS 8.6
This subcommand returns a description of the definition of the method named
\fImethod\fR of object \fIobject\fR. The defintion 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 \fBproc\fR or a method defintion,
and the second element is the body of the method.
.VE 8.6
.TP
\fBinfo object filters\fI object\fR
.VS 8.6
This subcommand returns the list of filter methods set on the object.
.VE 8.6
.TP
\fBinfo object forward\fI object method\fR
.VS 8.6
This subcommand returns the argument list for the method forwarding called
\fImethod\fR that is set on the object called \fIobject\fR.
.VE 8.6
.TP
\fBinfo object isa\fI category object\fR ?\fIarg\fR?
.VS 8.6
This subcommand tests whether an object belongs to a particular category,
returning a boolean value that indicates whether the \fIobject\fR argument
meets the criteria for the category. The supported categories are:
.VE 8.6
.RS
.TP
\fBinfo object isa class\fI object\fR
.VS 8.6
This returns whether \fIobject\fR is a class (i.e. an instance of
\fBoo::class\fR or one of its subclasses).
.VE 8.6
.TP
\fBinfo object isa metaclass\fI object\fR
.VS 8.6
This returns whether \fIobject\fR is a class that can manufacture classes
(i.e. is \fBoo::class\fR or a subclass of it).
.VE 8.6
.TP
\fBinfo object isa mixin\fI object class\fR
.VS 8.6
This returns whether \fIclass\fR is directly mixed into \fIobject\fR.
.VE 8.6
.TP
\fBinfo object isa object\fI object\fR
.VS 8.6
This returns whether \fIobject\fR really is an object.
.VE 8.6
.TP
\fBinfo object isa typeof\fI object class\fR
.VS 8.6
This returns whether \fIclass\fR is the type of \fIobject\fR (i.e. whether
\fIobject\fR is an instance of \fIclass\fR or one of its subclasses, whether
direct or indirect).
.RE
.VE 8.6
.TP
\fBinfo object methods\fI object\fR ?\fIoption...\fR?
.VS 8.6
This subcommand returns a list of all public (i.e. exported) methods of the
object called \fIobject\fR. Any of the following \fIoption\fRs may be
specified, controlling exactly which method names are returned:
.RS
.VE 8.6
.TP
\fB\-all\fR
.VS 8.6
If the \fB\-all\fR 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 superclasses of those classes.
.VE 8.6
.TP
\fB\-private\fR
.VS 8.6
If the \fB\-private\fR flag is given, the list of methods will also include
the private (i.e. non-exported) methods of the object (and classes, if
\fB\-all\fR is also given).
.RE
.VE 8.6
.TP
\fBinfo object mixins\fI object\fR
.VS 8.6
This subcommand returns a list of all classes that have been mixed into the
object named \fIobject\fR.
.VE 8.6
.TP
\fBinfo object variables\fI object\fR
.VS 8.6
This subcommand returns a list of all variables that have been declared for
the object named \fIobject\fR (i.e. that are automatically present in the
object's methods).
.VE 8.6
.TP
\fBinfo object vars\fI object\fR ?\fIpattern\fR?
.VS 8.6
This subcommand returns a list of all variables in the private namespace of
the object named \fIobject\fR. If the optional \fIpattern\fR argument is
given, it is a filter (in the syntax of a \fBstring match\fR glob pattern)
that constrains the list of variables returned. Note that this is different
from the lit returned by \fBinfo object variables\fR; that can include
variables that are currently unset, whereas this can include variables that
are not automatically included by any of \fIobject\fR's methods (or those of
its class, superclasses or mixins).
.VE 8.6
.SH EXAMPLES
.PP
This command prints out a procedure suitable for saving in a Tcl
script:
.PP
.CS
proc printProc {procName} {
    set result [list proc $procName]
    set formals {}
    foreach var [\fBinfo args\fR $procName] {
        if {[\fBinfo default\fR $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 [\fBinfo body\fR $procName]]
}
.CE
.SS "EXAMPLES WITH OBJECTS"
.VS 8.6
.PP
Every object necessarily knows what its class is; this information is
trivially extractable through introspection:
.CS
oo::class create c
c create o
puts [\fBinfo object class\fR o]
                     \fI\(-> prints "::c"\fR
puts [\fBinfo object class\fR c]
                     \fI\(-> prints "::oo::class"\fR
.CE
.PP
The introspection capabilities can be used to discover what class implements a
method and get how it is defined. This procedure illustrates how:
.CS
proc getDef {obj method} {
    if {$method in [\fBinfo object methods\fR $obj]} {
        # Assume no forwards
        return [\fBinfo object definition\fR $obj $method]
    }
    set cls [\fBinfo object class\fR $obj]
    while {$method ni [\fBinfo class methods\fR $cls]} {
        # Assume the simple case
        set cls [lindex [\fBinfo class superclass\fR $cls] 0]
        if {$cls eq {}} {
            error "no definition for $method"
        }
    }
    # Assume no forwards
    return [\fBinfo class definition\fR $cls $method]
}
.CE
.VE 8.6
.SH "SEE ALSO"
.VS 8.6
global(n), oo::class(n), oo::define(n), oo::object(n), proc(n), self(n)
.VE 8.6
.SH KEYWORDS
command, information, interpreter, introspection, level, namespace,
.VS 8.6
object,
.VE 8.6
procedure, variable
.\" Local Variables:
.\" mode: nroff
.\" End: