More Actions That Affect Control Flow
Just as break
was used in the rogue
script, so can all of the other flow-control commands be used inside of expect
commands. For example, a return
command inside of an expect
causes the current procedure to return:
proc foo { expect { "1" return "2" } someproc }
The continue
command causes control to resume at the beginning of the nearest enclosing while
or for
loop. continue
, break
, and return
can be mixed in intuitive ways. In the following example, the patterns 1
, 2
, and 3
do not mean anything in particular. They are just placeholders. The actions are what is interesting.
proc foo { while 1 { expect { "1" { return ;# return from foo } "2" { break ;# break out of while } "3" { if {0==[func]} { exit ;# exit program } else { continue ;# restart while } } } someproc } some-other-proc }
In Chapter 3 (p. 83), I showed a script that started an anonymous ftp
session and let you interact after performing the login automatically. Using some of the things you have seen since, it is possible to write a more capable version of aftp
. The one below retries the connection if the remote host refuses because it is down or there are too many users. A procedure called connect
is defined and called repeatedly in a loop. Anonymous ftp
administrators may not appreciate this approach, but it is sometimes the only way to get through to a site that is very popular. Once connected, the script sends the binary
command to disable any data conversions. As with the earlier ...
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