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The source code for Tcl is managed by fossil. Tcl developers coordinate all changes to the Tcl source code at

Tcl Source Code

Release Tcl 9.0.1 arises from the check-in with tag core-9-0-1.

Changes since Tcl 9.0.0

Release Tcl 9.0.0 arises from the check-in with tag core-9-0-0.

Highlighted differences between Tcl 9.0 and Tcl 8.6 are summarized below, with focus on changes important to programmers using the Tcl library and writing Tcl scripts.

Major Features

64-bit capacity: Data values larger than 2Gb

  • Strings can be any length (that fits in your available memory)
  • Lists and dictionaries can have very large numbers of elements

Internationalization of text

  • Full Unicode range of codepoints
  • New encodings: utf-16/utf-32/ucs-2(le|be), CESU-8, etc.
  • encoding options -profile, -failindex manage encoding of I/O.
  • msgcat supports custom locale search list
  • source defaults to -encoding utf-8

Zip filesystems and attached archives.

  • Packaging of the Tcl script library with the Tcl binary library, meaning that the TCL_LIBRARY environment variable is usually not required.
  • Packaging of an application into a virtual filesystem is now a supported core Tcl feature.

Unix notifiers available using epoll() or kqueue()

  • This relieves limits on file descriptors imposed by legacy select() and fixes a performance bottleneck.

Incompatibilities

Notable incompatibilities

  • Unqualified varnames resolved in current namespace, not global. Note that in almost all cases where this causes a change, the change is actually the removal of a latent bug.
  • No --disable-threads build option. Always thread-enabled.
  • I/O malencoding default response: raise error (-profile strict)
  • Windows platform needs Windows 7 or Windows Server 2008 R2 or later
  • Ended interpretation of ~ as home directory in pathnames. (See file home and file tildeexpand for replacements when you need them.)
  • Removed the identity encoding. (There were only ever very few valid use cases for this; almost all uses were systematically wrong.)
  • Removed the encoding alias binary to iso8859-1.
  • $::tcl_precision no longer controls string generation of doubles. (If you need a particular precision, use format.)
  • Removed pre-Tcl 8 legacies: case, puts and read variant syntaxes.
  • Removed subcommands [trace variable|vdelete|vinfo]
  • Removed -eofchar option for write channels.
  • On Windows 10+ (Version 1903 or higher), system encoding is always utf-8.
  • %b/%d/%o/%x format modifiers (without size modifier) for format and scan always truncate to 32-bits on all platforms.
  • %L size modifier for scan no longer truncates to 64-bit.
  • Removed command ::tcl::unsupported::inject. (See coroinject and coroprobe for supported commands with significantly more comprehensible semantics.)

Incompatibilities in C public interface

  • Extensions built against Tcl 8.6 and before will not work with Tcl 9.0; ABI compatibility was a non-goal for 9.0. In most cases, rebuilding against Tcl 9.0 should work except when a removed API function is used.

  • Many arguments expanded type from int to Tcl_Size, a signed integer type large enough to support 64-bit sized memory objects. The constant TCL_AUTO_LENGTH is a value of that type that indicates that the length should be obtained using an appropriate function (typically strlen() for char * values).

  • Ended support for Tcl_ChannelTypeVersion less than 5

  • Introduced versioning of the Tcl_ObjType struct

  • Removed macros CONST*: Tcl 9 support means dropping Tcl 8.3 support. (Replaced with standard C const keyword going forward.)

  • Removed registration of several Tcl_ObjTypes.

  • Removed API functions:

    Tcl_Backslash(), Tcl_*VA(), Tcl_*MathFunc*(), Tcl_MakeSafe(), Tcl_(Save|Restore|Discard|Free)Result(), Tcl_EvalTokens(), Tcl_(Get|Set)DefaultEncodingDir(), Tcl_UniCharN(case)cmp(), Tcl_UniCharCaseMatch()

  • Revised many internals; beware reliance on undocumented behaviors.

New Features

New commands

  • array default — Specify default values for arrays (note that this alters the behaviour of append, incr, lappend).
  • array for — Cheap iteration over an array's contents.
  • chan isbinary — Test if a channel is configured to work with binary data.
  • coroinject, coroprobe — Interact with paused coroutines.
  • clock add weekdays — Clock arithmetic with week days.
  • const, info const* — Commands for defining constants (variables that can't be modified).
  • dict getwithdefault — Define a fallback value to use when dict get would otherwise fail.
  • file home — Get the user home directory.
  • file tempdir — Create a temporary directory.
  • file tildeexpand — Expand a file path containing a ~.
  • info commandtype — Introspection for the kinds of commands.
  • ledit — Equivalent to lreplace but on a list in a variable.
  • lpop — Remove an item from a list in a variable.
  • lremove — Remove a sublist from a list in a variable.
  • lseq — Generate a list of numbers in a sequence.
  • package files — Describe the contents of a package.
  • string insert — Insert a string as a substring of another string.
  • string is dict — Test whether a string is a dictionary.
  • tcl::process — Commands for working with subprocesses.
  • *::build-info — Obtain information about the build of Tcl.
  • readFile, writeFile, foreachLine — Simple procedures for basic working with files.
  • tcl::idna::* — Commands for working with encoded DNS names.

New command options

  • chan configure ... -inputmode ... — Support for raw terminal input and reading passwords.
  • clock scan ... -validate ...
  • info loaded ... ?prefix?
  • lsearch ... -stride ... — Search a list by groups of items.
  • regsub ... -command ... — Generate the replacement for a regular expression by calling a command.
  • socket ... -nodelay ... -keepalive ...
  • vwait controlled by several new options
  • expr string comparators lt, gt, le, ge
  • expr supports comments inside expressions

Numbers

  • 0NNN format is no longer octal interpretation. Use 0oNNN.
  • 0dNNNN format to compel decimal interpretation.
  • NN_NNN_NNN, underscores in numbers for optional readability
  • Functions: isinf(), isnan(), isnormal(), issubnormal(), isunordered()
  • Command: fpclassify
  • Function int() no longer truncates to word size

TclOO facilities

  • private variables and methods
  • class variables and methods
  • abstract and singleton classes
  • configurable properties
  • method -export, method -unexport

Known bugs