I'm assuming that's a space between -u and http://your ip address:6077/xmltv.xml.
The TVHeadend log shows:
2021-06-06 14:51:27.813 xmltv: /storage/.kodi/addons/service.tvheadend42/bin/tv_grab_url: grab /storage/.kodi/addons/service.tvheadend42/bin/tv_grab_url
2021-06-06 14:51:27.824 spawn: Executing "/storage/.kodi/addons/service.tvheadend42/bin/tv_grab_url"
2021-06-06 14:51:27.833 spawn: /storage/.kodi/addons/service.tvheadend42/bin/tv_grab_url: line 6: can't open 1: no such file
2021-06-06 14:51:27.841 spawn: wget: unrecognized option '--retry-connrefused'
2021-06-06 14:51:27.844 spawn: BusyBox v1.32.1 (2021-06-06 11:42:06 CEST) multi-call binary.
2021-06-06 14:51:27.844 spawn: Usage: wget [-c|--continue] [--spider] [-q|--quiet] [-O|--output-document FILE]
2021-06-06 14:51:27.844 spawn: [-o|--output-file FILE] [--header 'header: value'] [-Y|--proxy on/off]
2021-06-06 14:51:27.844 spawn: [--no-check-certificate]
2021-06-06 14:51:27.844 spawn: [-P DIR] [-S|--server-response] [-U|--user-agent AGENT] [-T SEC] URL...
2021-06-06 14:51:27.844 spawn: Retrieve files via HTTP or FTP
2021-06-06 14:51:27.844 spawn: --spider Only check URL existence: $? is 0 if exists
2021-06-06 14:51:27.844 spawn: --no-check-certificate Don't validate the server's certificate
2021-06-06 14:51:27.844 spawn: -c Continue retrieval of aborted transfer
2021-06-06 14:51:27.844 spawn: -q Quiet
2021-06-06 14:51:27.844 spawn: -P DIR Save to DIR (default .)
2021-06-06 14:51:27.844 spawn: -S Show server response
2021-06-06 14:51:27.844 spawn: -T SEC Network read timeout is SEC seconds
2021-06-06 14:51:27.844 spawn: -O FILE Save to FILE ('-' for stdout)
2021-06-06 14:51:27.844 spawn: -o FILE Log messages to FILE
2021-06-06 14:51:27.844 spawn: -U STR Use STR for User-Agent header
2021-06-06 14:51:27.844 spawn: -Y on/off Use proxy
2021-06-06 14:51:27.845 xmltv: /storage/.kodi/addons/service.tvheadend42/bin/tv_grab_url: no output detected
2021-06-06 14:51:27.845 xmltv: /storage/.kodi/addons/service.tvheadend42/bin/tv_grab_url: grab returned no data
When I type the command: ./tv_grab_url -u http://192.168.1.83:6077/xmltv/xml
I get the below response:
CoreELEC:~/.kodi/addons/service.tvheadend42/bin # ./tv_grab_url -u
http://192.168.1.83:6077/xmltv/xml
./tv_grab_url: line 6: can't open 1: no such file
wget: unrecognized option '--retry-connrefused'
BusyBox v1.32.1 (2021-06-06 11:42:06 CEST) multi-call binary.
Usage: wget [-c|--continue] [--spider] [-q|--quiet] [-O|--output-document FILE]
[-o|--output-file FILE] [--header 'header: value'] [-Y|--proxy on/off]
[--no-check-certificate]
[-P DIR] [-S|--server-response] [-U|--user-agent AGENT] [-T SEC] URL...
Retrieve files via HTTP or FTP
--spider Only check URL existence: $? is 0 if exists
--no-check-certificate Don't validate the server's certificate
-c Continue retrieval of aborted transfer
-q Quiet
-P DIR Save to DIR (default .)
-S Show server response
-T SEC Network read timeout is SEC seconds
-O FILE Save to FILE ('-' for stdout)
-o FILE Log messages to FILE
-U STR Use STR for User-Agent header
-Y on/off Use proxy
Line 6 of my tv_grab_url file is:
if (( $# < 1 ))