'''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.

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'''package names''' will only deliver all available packages if it has searched all package indices before. To force this, do a dummy '''[package require]''' before:

 catch {package require nonexistentName}
 package names

'''[DGP]''' - To be more precise, [[package names]] returns a list of all the package names that are already known to the [[package]] command. That is not the same as all the names that could become known by operation of the [[package unknown]] callback.

The default [[package unknown]] callback is [[tclPkgUnknown]] and it is that default callback that exhibits the behavior described above -- after one run, all installed package names are known. The [[package unknown]] interface does not require that behavior, and other callbacks may not (IMHO, should not) implement it.

[Lars H]: Feeling slightly Cantorian, I'd propose the following for a foolproof (never loading a package, even if it's got a bizarre name) method of listing all package names:
  proc all_package_names {} {
     if {[package unknown] eq ""} then {
        return [package names]
     }
     set res ""
     while {$res ne [set res [package names]]} {
        uplevel #0 [package unknown] [list $res+1 ""]
     }
     return $res
  }
The idea is that "[[package names]]+1" cannot be the name of a package known to the package database, so telling [package unknown] to search for it will force some additional data to be entered, even for a very lazy package unknown handler.

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See also:

   * [package]
   * [package provide]
   * [package require]
   * [package unknown]
   * [package versions]

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