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Regexp and expect

Posted by johnjacky (johnjacky), 30 September 2005
I am very newbie to Expect started on a day back.. I am not a hardcore programmer  even. But a newbie to programming even.

May I have some help , from you on finding a regex which matches the below expressions,

[root@calgary ~]#
[jj@projeon jj]$

I tried using expect -re "\[root" (It didn't work and was throwing errors]
I tried using expect -re "\u001b]0;root" [it did work, but it will only match if the user is root)

I want to send some commands , if it matches like  "^\[A-Za-z0-9@" How can I use a such a pattern with expect ? i.e if the line starts with --> [username@  <--, I would like to send some commands

Thanks in advance,
Masters help!!!!

Posted by johnjacky (johnjacky), 30 September 2005
Also if anyone could tell me why I need \u001b ( [for Control + [)  and ]0; in the regexp match of "[root" . Not sure what is the meaning of unicode ]0; Is there any util for knowing that ? I will much appreciate if anyone could help me on it.

And for a solution, ofcourse I can use the expect -re "(%|#|>|\\\$) $". Taken from the forums itself Thanks.

Posted by admin (Graham Ellis), 1 October 2005
I think you want to write something like


as your regular expression.   Depending on how you protect it, the [ character can mean any one of three things in the regular expression area of Tcl / expect program:

1. Without and protection from the Tcl interpretter, it means "run the command in these square brackets first, and substitute the result into the command.  Thus ...

set fred [clock seconds]
puts $fred

2. Within a regular expression (typically protected from the Tcl interpretter using double quotes or curly braces), a list of characters in square brackets matches any one character from the list.

3. Within a regular expression, and protected from the Tcl interpretter as described just above AND protected from the regular expression handler with a \ character, you can look literally for the [ character.

Here's an example piece of code that matches the [username@ sequence in a Tcl regular expression:

gets stdin stuff
puts $stuff

if {[regexp {\[[a-z0-9]+@} $stuff found]} {
       puts "yes - $found"
} else {
       puts "no"

That's a complete, tested program.

Your use of unicode characters is fair enough - it could be easier that way in some circumstances as it avoids the needs for quite as much protection of special characters from the various interpretters.

Posted by Custard (Custard), 1 October 2005
Hi, the control characters you mention look like the ANSI escape sequence to make the prompt appear a different colour.
ANSI escapes begin with an ESC (0x1b) followed by a code or codes terminated by a semicolon (



Posted by johnjacky (johnjacky), 2 October 2005
WOW..this is simply superb..I never expected such a response like this...Simply excelltent..If I was somewhere at UK, I wouldn't have had a second thought to get trained in programming concepts. Thanks Graham..Thanks Custard too...

May I have one more help, please..I am not sure whether this is a bug or any work around possible for this..My code snippet is as below,

expect -re "connecting (yes/no)?" {
               send -- "yes\r"
               expect -nocase -re "password:"
               send "{[lindex $argv 1]}\r"
                       } -nocase -re "password:" {
                       send -- "{[lindex $argv 1]}\r"

Everything works except when I give the pass as something like --> p0lic3%$# <-- It is getting interpretted as p0lic3%0. The exact message when I turn on the exp_internal is

send: sending "{p0lic3%0}\r" to { exp4 }

How can I make the expect program take the pass as it is ?

Thanks a bunch

Posted by admin (Graham Ellis), 2 October 2005
I notice that you're picking up the password from the command line (argv).   With most command line interpretters (shell programs), the # character means that it's the start of a comment which will get stripped out before it even gets to Tcl, and I suspect this may be your problem.

Suggestion - print out (JUST for testing as people hate to have their passwords echoed in plain text) $argv in you Tcl and see what you've actually got there.   Once we know if it's a Tcl or shell problem, we can look for an appropriate solution.

Posted by johnjacky (johnjacky), 2 October 2005
yes that was the issue Thank you once again.

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