The following global variables have special meaning to the Tcl interpreter:
argc
Number of command-line arguments, not including the name of the script file (tclsh)
argv
List containing command-line arguments (tclsh)
argv0
Filename being interpreted, or name by which script was invoked (tclsh)
env
Array in which each element name is an environment variable
errorCode
Error code information from last Tcl error
errorInfo
Describes the stack trace of the last Tcl error
tcl_interactive
Set to 1 if running interactively, 0 otherwise (tclsh)
tcl_library
tcl_pkgPath
tcl_patchLevel
Current patch level of Tcl interpreter
tcl_platform
Array with elements byteOrder
,
machine
, osVersion
,
platform
, and os
tcl_precision
Number of significant digits to retain when converting floating-point numbers to strings (default 12)
tcl_prompt1
Primary prompt (tclsh)
tcl_prompt2
Secondary prompt for incomplete commands (tclsh)
tcl_rcFileName
The name of a user-specific startup file
tcl_traceCompile
Controls tracing of bytecode compilation; 0 for no output, 1 for summary, and 2 for detailed
tcl_traceExec
Controls tracing of bytecode execution; 0 for no output, 1 for summary, and 2 for detailed
tcl_version
Current version of Tcl interpreter