- package forget ?package package ...?
-
Removes all information about each specified package from this interpreter,
including information provided by both package ifneeded and
package provide.
- package ifneeded package version ?script?
-
This command typically appears only in system configuration
scripts to set up the package database.
It indicates that a particular version of
a particular package is available if needed, and that the package
can be added to the interpreter by executing script.
The script is saved in a database for use by subsequent
package require commands; typically, script
sets up auto-loading for the commands in the package (or calls
load and/or source directly), then invokes
package provide to indicate that the package is present.
There may be information in the database for several different
versions of a single package.
If the database already contains information for package
and version, the new script replaces the existing
one.
If the script argument is omitted, the current script for
version version of package package is returned,
or an empty string if no package ifneeded command has
been invoked for this package and version.
- package names
-
Returns a list of the names of all packages in the
interpreter for which a version has been provided (via
package provide) or for which a package ifneeded
script is available.
The order of elements in the list is arbitrary.
- package present ?-exact? package ?version?
-
This command is equivalent to package require except that it
does not try and load the package if it is not already loaded.
- package provide package ?version?
-
This command is invoked to indicate that version version
of package package is now present in the interpreter.
It is typically invoked once as part of an ifneeded script,
and again by the package itself when it is finally loaded.
An error occurs if a different version of package has been
provided by a previous package provide command.
If the version argument is omitted, then the command
returns the version number that is currently provided, or an
empty string if no package provide command has been
invoked for package in this interpreter.
- package require -exact package version
-
This form of the command is translated to the form below using the
bounded requirement "version-(version+1)", making only the given
version acceptable, within the specified level of detail. Deeper
levels are allowed to vary. Examples:
-exact 8 => 8-9
-exact 8.4 => 8.4-8.5
-exact 8.4.14 => 8.4.14-8.4.15
-
For more explanations see below.
- package require package ?requirement...?
-
This command is typically invoked by Tcl code that wishes to use
a particular version of a particular package. The arguments
indicate which package is wanted, and the command ensures that
a suitable version of the package is loaded into the interpreter.
If the command succeeds, it returns the version number that is
loaded; otherwise it generates an error.
A suitable version of the package is any version which satisfies at
least one of the requirements, per the rules of package
vsatisfies. If multiple versions are suitable the implementation
with the highest version is chosen. This last part is additionally
influenced by the selection mode set with package prefer.
In the "stable" selection mode the command will select the highest
stable version satisfying the requirements, if any. If no stable
version satisfies the requirements, the highest unstable version
satisfying the requirements will be selected. In the "latest"
selection mode the command will accept the highest version satisfying
all the requirements, regardless of its stableness.
If a version of package has already been provided (by invoking
the package provide command), then its version number must
satisfy the requirements and the command returns immediately.
Otherwise, the command searches the database of information provided by
previous package ifneeded commands to see if an acceptable
version of the package is available.
If so, the script for the highest acceptable version number is evaluated
in the global namespace;
it must do whatever is necessary to load the package,
including calling package provide for the package.
If the package ifneeded database does not contain an acceptable
version of the package and a package unknown command has been
specified for the interpreter then that command is evaluated in the
global namespace; when
it completes, Tcl checks again to see if the package is now provided
or if there is a package ifneeded script for it.
If all of these steps fail to provide an acceptable version of the
package, then the command returns an error.
- package unknown ?command?
-
This command supplies a ``last resort'' command to invoke during
package require if no suitable version of a package can be found
in the package ifneeded database.
If the command argument is supplied, it contains the first part
of a command; when the command is invoked during a package require
command, Tcl appends one or more additional arguments giving the desired
package name and requirements.
For example, if command is foo bar and later the command
package require test 2.4 is invoked, then Tcl will execute
the command foo bar test 2.4 to load the package.
If no requirements are supplied to the package require command,
then only the name will be added to invoked command.
If the package unknown command is invoked without a command
argument, then the current package unknown script is returned,
or an empty string if there is none.
If command is specified as an empty string, then the current
package unknown script is removed, if there is one.
- package vcompare version1 version2
-
Compares the two version numbers given by version1 and version2.
Returns -1 if version1 is an earlier version than version2,
0 if they are equal, and 1 if version1 is later than version2.
- package versions package
-
Returns a list of all the version numbers of package
for which information has been provided by package ifneeded
commands.
- package vsatisfies version requirement...
-
Returns 1 if the version satisfies at least one of the given
requirements, and 0 otherwise. Each requirement is allowed to
have any of the forms:
- min
-
This form is called "min-bounded".
- min-
-
This form is called "min-unbound".
- min-max
-
This form is called "bounded".
where "min" and "max" are valid version numbers. The legacy syntax is
a special case of the extended syntax, keeping backward
compatibility. Regarding satisfaction the rules are:
- [1]
-
The version has to pass at least one of the listed
requirements to be satisfactory.
- [2]
-
A version satisfies a "bounded" requirement when
- [a]
-
For min equal to the max if, and only if the version
is equal to the min.
- [b]
-
Otherwise if, and only if the version is greater than or equal
to the min, and less than the max, where both min
and max have been padded internally with 'a0'. Note that while
the comparison to min is inclusive, the comparison to
max is exclusive.
- [3]
-
A "min-bounded" requirement is a "bounded" requirement in disguise,
with the max part implicitly specified as the next higher major
version number of the min part. A version satisfies it per the
rules above.
- [4]
-
A version satisfies a "min-unbound" requirement if, and only if
it is greater than or equal to the min, where the min has
been padded internally with 'a0'. There is no constraint to a maximum.
- package prefer ?latest|stable?
-
With no arguments, the commands returns either "latest" or "stable",
whichever describes the current mode of selection logic used by
package require.
When passed the argument "latest", it sets the selection logic mode to
"latest".
When passed the argument "stable", if the mode is already "stable",
that value is kept. If the mode is already "latest", then the attempt
to set it back to "stable" is ineffective and the mode value remains
"latest".
When passed any other value as an argument, raise an invalid argument
error.
When an interpreter is created, its initial selection mode value is set to
"stable" unless the environment variable TCL_PKG_PREFER_LATEST
is set. If that environment variable is defined (with any value) then
the initial (and permanent) selection mode value is set to "latest".
To test to see if the Snack package is available and load if it is
(often useful for optional enhancements to programs where the loss of
the functionality is not critical) do this: