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tm(3tcl) | Tcl Built-In Commands | tm(3tcl) |
NAME¶
tm - Facilities for locating and loading of Tcl ModulesSYNOPSIS¶
::tcl::tm::path add ?path...? ::tcl::tm::path remove ?path...? ::tcl::tm::path list ::tcl::tm::roots ?path...?
DESCRIPTION¶
This document describes the facilities for locating and loading Tcl Modules (see MODULE DEFINITION for the definition of a Tcl Module). The following commands are supported:- ::tcl::tm::path add ?path...?
- The paths are added at the head to the list of module paths, in order of appearance. This means that the last argument ends up as the new head of the list.
The command enforces the restriction that no path may be an ancestor directory
of any other path on the list. If any of the new paths violates this
restriction an error will be raised, before any of the paths have been added.
In other words, if only one path argument violates the restriction then none
will be added.
If a path is already present as is, no error will be raised and no action will
be taken.
Paths are searched later in the order of their appearance in the list. As they
are added to the front of the list they are searched in reverse order of
addition. In other words, the paths added last are looked at first.
- ::tcl::tm::path remove ?path...?
- Removes the paths from the list of module paths. The command silently ignores all paths which are not on the list.
- ::tcl::tm::path list
- Returns a list containing all registered module paths, in the order that they are searched for modules.
- ::tcl::tm::roots ?path...?
- Similar to path add, and layered on top of it. This command takes a list of paths, extends each with “ tclX/site-tcl”, and “ tclX /X.y”, for major version X of the Tcl interpreter and minor version y less than or equal to the minor version of the interpreter, and adds the resulting set of paths to the list of paths to search.
This command is used internally by the system to set up the system-specific
default paths.
The command has been exposed to allow a build system to define additional root
paths beyond those described by this document.
MODULE DEFINITION¶
A Tcl Module is a Tcl Package contained in a single file, and no other files required by it. This file has to be sourceable. In other words, a Tcl Module is always imported via:source module_file
([_[:alpha:]][:_[:alnum:]]*)-([[:digit:]].*)\.tm
package vcompare $version 0
FINDING MODULES¶
The directory tree for storing Tcl modules is separate from other parts of the filesystem and independent of auto_path. Tcl Modules are searched for in all directories listed in the result of the command ::tcl::tm::path list. This is called the Module path. Neither the auto_path nor the tcl_pkgPath variables are used. All directories on the module path have to obey one restriction:
For any two directories, neither is an ancestor directory of the other.
This is required to avoid ambiguities in package naming. If for example the two
directories “ foo/” and “ foo/cool”
were on the path a package named cool::ice could be found via the names
cool::ice or ice, the latter potentially obscuring a package
named ice, unqualified.
Before the search is started, the name of the requested package is translated
into a partial path, using the following algorithm:
All occurrences of “ ::” in the package name are replaced
by the appropriate directory separator character for the platform we are on.
On Unix, for example, this is “ /”.
Example:
The requested package is encoding::base64. The generated partial path is
“ encoding/base64”.
After this translation the package is looked for in all module paths, by
combining them one-by-one, first to last with the partial path to form a
complete search pattern. Note that the search algorithm rejects all files
where the filename does not match the regular expression given in the section
MODULE DEFINITION. For the remaining files provide scripts are
generated and added to the package ifneeded database.
The algorithm falls back to the previous unknown handler when none of the found
module files satisfy the request. If the request was satisfied the fall-back
is ignored.
Note that packages in module form have no control over the index
and provide scripts entered into the package database for them. For a
module file MF the index script is always:
package ifneeded PNAME PVERSION [list source MF]
source MF
MF = /module_path/PNAME′-PVERSION.tm
DEFAULT PATHS¶
The default list of paths on the module path is computed by a tclsh as follows, where X is the major version of the Tcl interpreter and y is less than or equal to the minor version of the Tcl interpreter. All the default paths are added to the module path, even those paths which do not exist. Non-existent paths are filtered out during actual searches. This enables a user to create one of the paths searched when needed and all running applications will automatically pick up any modules placed in them. The paths are added in the order as they are listed below, and for lists of paths defined by an environment variable in the order they are found in the variable.SYSTEM SPECIFIC PATHS¶
- file normalize [info library]/../tclX/X. y
- In other words, the interpreter will look into a directory specified by its major version and whose minor versions are less than or equal to the minor version of the interpreter.
For example for Tcl 8.4 the paths searched are:
This definition assumes that a package defined for Tcl X.y
can also be used by all interpreters which have the same major number X
and a minor number greater than y.
[info library]/../tcl8/8.4 [info library]/../tcl8/8.3 [info library]/../tcl8/8.2 [info library]/../tcl8/8.1 [info library]/../tcl8/8.0
- file normalize EXEC/tclX/X.y
- Where EXEC is file normalize [info nameofexecutable]/../lib or file normalize [::tcl::pkgconfig get libdir,runtime]
This sets of paths is handled equivalently to the set coming before, except that
it is anchored in EXEC_PREFIX. For a build with PREFIX =
EXEC_PREFIX the two sets are identical.
SITE SPECIFIC PATHS¶
- file normalize [info library]/../tclX/site-tcl
- Note that this is always a single entry because X is always a specific value (the current major version of Tcl).
USER SPECIFIC PATHS¶
- $::env(TCLX_y_TM_PATH)
- A list of paths, separated by either : (Unix) or ; (Windows). This is user and site specific as this environment variable can be set not only by the user's profile, but by system configuration scripts as well.
- $::env(TCLX.y_TM_PATH)
- Same meaning and content as the previous variable. However the use of dot '.' to separate major and minor version number makes this name less to non-portable and its use is discouraged. Support of this variable has been kept only for backward compatibility with the original specification, i.e. TIP 189.
$::env(TCL8.4_TM_PATH) $::env(TCL8_4_TM_PATH) $::env(TCL8.3_TM_PATH) $::env(TCL8_3_TM_PATH) $::env(TCL8.2_TM_PATH) $::env(TCL8_2_TM_PATH) $::env(TCL8.1_TM_PATH) $::env(TCL8_1_TM_PATH) $::env(TCL8.0_TM_PATH) $::env(TCL8_0_TM_PATH)
SEE ALSO¶
package(3tcl), Tcl Improvement Proposal #189 “ Tcl Modules” (online at http://tip.tcl.tk/189.html), Tcl Improvement Proposal #190 “ Implementation Choices for Tcl Modules” (online at http://tip.tcl.tk/190.html)KEYWORDS¶
modules, package8.5 | Tcl |