OK.
I've just solved the problem,
In short, what happened was that 7
hidden characters were appended just before the beginning of the $CHANNEL value.
I checked the string-lenght of $CHANNEL and to my surprise it showed 24, while only 17 were visible:
root@codeplace:~# asterisk -rx "core show channels concise"
SIP/1001-00000175!default!124!7!Ring!Playback!holdmusic,noanswer!1001!!!3!8!(None)!1355439097.373
root@codeplace:~# echo $CHANNEL
SIP/1001-00000175
root@codeplace:~# echo $CHANNEL | awk '{print length}'
24
If you wondered what were these hidden characters here it is (time info?):
root@codeplace:~# echo ${CHANNEL:0}
SIP/1001-00000175
root@codeplace:~# echo ${CHANNEL:1}
[0;37mSIP/1001-00000175
Anyway, for hanging it up from bash shell, $CHANNEL variable must started from its position number 7:
root@codeplace:~# CHANNEL=`asterisk -rx "core show channels concise" | grep 124 | cut -f1 -d'!'`; asterisk -rx "channel request hangup ${CHANNEL:7}"
Requested Hangup on channel 'SIP/1001-00000175'
Hope this help someone :-)
