Regsub not manipulating string from URL - tcl

Question

I am getting a strange TCL error when using this iRule, the error is:
<HTTP_REQUEST> - ERR_ARG (line 2) invoked from within "HTTP::uri
[regsub "/3dnotification" [HTTP::uri] ""] "
This is an F5 irule code.
This what I have tried:
when HTTP_REQUEST
{
if { not ( [string tolower [HTTP::uri]] starts_with "/socket.io" )} then {
HTTP::uri [regsub "/3dnotification" [HTTP::uri] ""]
# need to strip trailing slash on URI otherwise results in 404 for resources...
HTTP::uri [regsub "\/$" [HTTP::uri] ""]
} elseif { [string tolower [HTTP::header Upgrade]] contains "websocket" } {
ONECONNECT::reuse disable
set oc_reuse_disable 1
}
HTTP::header replace "X-Forwarded-ContextPath" "/"
}
when SERVER_CONNECTED {
if { [info exists oc_reuse_disable] } {
# Optional; unnecessary if the HTTP profile is disabled (goes into passthrough mode).
ONECONNECT::detach disable
unset oc_reuse_disable
}
}

Answer 1

Since the URI is either a full URI or the protocol-less part (I can't quite tell which from what you say; I'll assume either is possible), removing a leading part or trailing part is going to be a little bit tricky. What you need to do is to first split the URI into its component parts, apply the transformation to the path part, and then reassemble. The key to the splitting and reassembly is the uri package in Tcllib.
package require uri
# Split the URI and pick out the path from the parts
set uriParts [uri::split [HTTP::uri]]
set path [dict get $uriParts path]
# Do the transforms
set path [regsub "/3dnotification" $path ""]
set path [string trimright $path "/"]; # A different way to remove trailing slashes
# Reassemble and write back
dict set uriParts path $path
HTTP::uri [uri::join {*}$uriParts]
I'm assuming that you'd put the package require (or whatever else you need in order to get the code present) at the top of the script, and the rest inside the right when clause(s).
So that you can see what URI splitting actually does, here's your example URI split (in an interactive tclsh session):
% set uri "http://www.example.com:8080/main/index.jsp?user=test&login=check"
http://www.example.com:8080/main/index.jsp?user=test&login=check
% uri::split $uri
fragment {} port 8080 path main/index.jsp scheme http host www.example.com query user=test&login=check pbare 0 pwd {} user {}
As you can see, the path part is just main/index.jsp which is enormously easier to work with than the whole URI.