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The textport lets you type HScript commands and prints the results.


You can start typing your next command while the previous command is executing.

To...Do this

Quickly paste text from the output of a previous command in the current command line

  1. Select the text you want to paste.

  2. Click MMB.

Scroll the textport window

  • Drag RMB to scroll up and down.

  • Press PgUp or PgDn.

  • Press Home to scroll the top of the window. Press End to scroll to the end.


Expansion is done in the following order:

  1. History substitution.

  2. Alias expansion.

  3. Variables and expressions.

History substitution

Certain text patterns on the command line are replaced with the text of previous commands. These are mostly useful for people who are used to using the similar feature in UNIX shells. For most people, simply scrolling through the history with and is faster.


Repeat last command.


Repeat last command containing string.


Repeat the nth command. To print a numbered command history, use the history command.


Repeat the command run n commands ago.

Alias expansion

You can define an alias that stands for another string. This is useful for replacing long, frequently used command lines with a short name.

You can define aliases with the alias command, or in the Aliases and Variables window (Window ▸ Aliases and Variables).


Houdini does not support nested aliases. The definition of an alias cannot itself contain an alias.


  • The maximum line length (after expansion) for a Houdini command is 8 Kb.

  • The maximum number of arguments on a command line is 1024.

  • The maximum number of number of nested if statements in a single source file is 128.

  • The maximum number of source files is limited by the system limit on open files.

  • There is no limit for nested loops.

  • Linux: Due to event handling problems in the implementation of X Windows, Houdini turns the keyboard key repeat off while the cursor is inside one of the 3D Viewports and on again when the cursor leaves a Viewport.

    If you find the key repeat is off on your system, run the xset r on command to turn key repeat on again.