The previous example was very simple-minded. The characters from the output of the spawned processes were copied to their own text widget. The only attempt at formatting was to handle line endings. Most programs expect more than this. For example, tabs are usually expanded to spaces, and backspaces cause the terminal cursor to move left instead of right.
More sophisticated programs require character addressing. By sending special terminal manipulation character sequences (I will just call them sequences from now on), programs can write to arbitrary character locations on the screen. The following terminal emulator supports this. You can use it to run programs such as
As before, a text widget is used for display. Its name is stored in the variable
term. For simplicity, the code only supports a single emulator, assumes a fixed size display of 24 rows of 80 columns, and runs a shell. The following code starts the process and creates the text widget.
# tkterm - term emulator using Expect and Tk text widget set rows 24 ;# number of rows in term set cols 80 ;# number of columns in term set term .t ;# name of text widget used by term log_user 0 # start a shell and text widget for its output set stty_init "-tabs" eval spawn $env(SHELL) stty rows $rows columns $cols < $spawn_out(slave,name) set term_spawn_id $spawn_id text $term -width $cols -height $rows
Once the terminal widget has been created, it can be displayed on the screen with a