Expect script fails to show file exist failure

edomingox · 03-27-2009, 02:47 PM

I have this script to check if a file exists. The first "if" statement just makes sure that the file was entered in the command line. That works fine. Where it fails is the next step. I call the "ls" command just to find the file. That works if the file was there. It would show this:

# expect pass_manager.exp /etc/hosts
/etc/hosts

Now when I put a file that doesn't exist into the command line, I'm expecting to see the "does not exist" line to show. But I only get this:

# expect pass_manager.exp hosts
ls: cannot access hosts: No such file or directory

Is there something that I'm missing? What I'm really looking for is a way to expect script a way to check if a file exists. And there are not many good tutorials out there that I can find.

Code:

set hostFile [lindex $argv 0]
if {$hostFile == ""} {
	send_user "Usage: expect pass_manager \[FILE\]\n"
	send_user "    \[FILE\]       file containing list of hosts\n"
	exit
}
set timeout 3
spawn -noecho ls $hostFile
expect {
	"No such file or directory" {
		send "does not exist\n"
	}	
}

taylor_venable · 03-27-2009, 09:41 PM

I don't really know Expect but I believe it has full Tcl behind it right? How about just:

Code:

if {![file exists $hostFile]} {
  # It's not there.
}

http://www.tcl.tk/man/tcl8.5/TclCmd/contents.htm

jlinkels · 03-28-2009, 08:37 AM

What you see is the return string of ls. That is correct.

If you receive "No such file", Expect will send "does not exist" the the connection it just opened. Since that connection is just closed as ls terminated.

A solution like taylor gave should work if you just want to check for file existence in tcl. If your goal is to use Expect anyway and communciate thru shell commands, make sure you set set exp_interal 1 to see what is happening back and forth the command you sent.

Without exp_internal you are clueless about what expect receives and how it is interpreted.

jlinkels

edomingox · 03-29-2009, 07:11 PM

Quote:

Originally Posted by jlinkels

If you receive "No such file", Expect will send "does not exist" the the connection it just opened. Since that connection is just closed as ls terminated.
jlinkels

That makes sense. I will try Taylor's method.

edit: It worked perfectly. I'll have to try to figure out the way expect works a bit better. Can't really find any good tutorials on it. I may have to look up some tcl tutorials.