I've been creating some basic system health checks, and one of the checks includes a yum repo health status that uses one of Chef's tools called 'knife'. However, when I try to awk a column, I get
can't read "4": no such variable.
Here is what I am currently using:
read -s -p "enter password: " pass
/usr/bin/expect << EOF
spawn knife ssh -m host1 "sudo bash -c \"yum repolist -v| grep Repo-name| awk '{print $4}'\" "
expect {
-nocase password: { send "$pass\r" }; expect eof }
}
EOF
I've tried other variations as well, such as replacing the awk single quotes with double curly braces, escaping the variable, and even setting the variable to the command, and keep getting the same negative results:
awk {{print $4}}
awk '{print \$4}'
awk '\{print \$4\}'
awk {\{print \$4\}}
Does anyone know how I can pass this awk column selector variable within a spawned knife ssh command that sends the variable to the ssh host?
This line:
spawn knife ssh -m host1 "sudo bash -c \"yum repolist -v|grep Repo-name|awk '{print $4}'\""
has many layers of quoting (Tcl/Expect, ssh, bash, awk), and it's quoting of different types. Such things are usually pretty nasty and can require using rather a lot of backslashes to persuade values to go through the outer layers unmolested. In particular, Tcl and the shell both want to get their hands on variables whose uses start with $ and continue with alphanumerics. (Backslashes that go in deep need to be themselves quoted with more backslashes, making the code hard to read and hard to understand precisely.)
spawn knife ssh -m host1 "sudo bash -c \"yum repolist -v|grep Repo-name|awk '{print \\\$4}'\""
However, there's one big advantage available to us: we can put much of the code into braces at the outer level as we are not actually substituting anything from Tcl in there.
spawn knife ssh -m host1 {sudo bash -c "yum repolist -v|grep Repo-name|awk '{print \$4}'"}
The thing inside the braces is conventional shell code, not Tcl. And in fact we can probably simplify further, as neither grep nor awk need to be elevated:
spawn knife ssh -m host1 {sudo bash -c "yum repolist -v"|grep Repo-name|awk '{print $4}'}
Depending on the sudo configuration, you might even be able to do this (which I'd actually rather people did on systems I controlled anyway, rather than giving general access to root shells out):
spawn knife ssh -m host1 {sudo yum repolist -v|grep Repo-name|awk '{print $4}'}
And if my awk is good enough, you can get rid of the grep like this:
spawn knife ssh -m host1 {sudo yum repolist -v|awk '/Repo-name/{print $4}'}
This is starting to look more manageable. However, if you want to substitute Repo-name for a Tcl variable, you need a little more work that reintroduces a backslash, but now it is all much tamer than before as there's fewer layers of complexity to create headaches.
set repo "Repo-name"
spawn knife ssh -m host1 "sudo yum repolist -v|awk '/$repo/{print \$4}'"
In practice, I'd be more likely to get rid of the awk entirely and do that part in Tcl code, as well as setting up key-based direct access to the root account, allowing avoiding the sudo, but that's getting rather beyond the scope of your original question.