Additional Tcl Details

String Manipulation:

    regexp    format    split     string
    regsub    scan      join

File I/O:

    open      gets      seek      flush     glob
    close     read      tell      cd
    puts      source    eof       pwd

Error Handling:

    catch     error     errInfo

Subprocesses:

    exec grep foo << $input | wc

Associative Arrays:

    set x(fred) 44
    set x(2) [expr $x(fred) + 6]

Variable Scoping:

	global    uplevel   upvar

Access to Tcl internals:

	info      rename    trace

Autoloading:

• The unknown procedure is invoked when a command doesn't exist.
• Loads procedures on demand from libraries.
• Uses a search path of directories.

More on substitutions:

• Keep substitutions simple: use commands like format for complex arguments.
• Use eval for another level of expansion:

  exec rm *.o

  
  *.o: No such file or directory

  glob *.o

  
  a.o b.o

  exec rm [glob *.o]

  
  a.o b.o: No such file or directory

  eval exec rm [glob *.o]

Commands and Lists:

• Lists parse cleanly as commands: each element becomes one word.
• To create commands safely, use list commands:

  button .b -text Reset -command {set x $initValue}

  
  Oops! initValue read later, when button invoked.

  ...-command "set x $initValue"

  
  Oops! Fails if initValue contains ``New York''

  ...-command "set x {$initValue}"

  
  Oops! Fails if initValue contains ``{''

  ...-command [list set x $initValue]

  
  OK. Always works.