http://www.purl.org/tcl/home/man/tcl8.4/TclCmd/tclvars.htm
$::errorCode contains error information in various cases (see the man page above); one of these cases is the exit status of the last exec or open "|..."/close pair that received an error.
See also tclvars, error, errorInfo, and return.
Anyone have good programming practices for using this? (The exec page gives a start at handling $::errorCode for [exec] or [open "|..."].)
DKF writes in Interrupting loops:
One way to encourage setting the errorCode would be to propose additional error classes. The standard ARITH, CHILD*, NONE, and POSIX only cover a fraction of all possible error conditions.
How about:
More?
[Say a few words on how errorCode is currently used, and not used, and how it might be better used. Relate to discussion [L1 ].]
"expect_out(buffer) has the content of the previous send"