regex - problems with a regular expression -

i'm trying correct regular expression problem:

i result webservice string looks this

tag: 54e16e66 (mifare card standard)

i need extract 54e16e66 part (which in hexa) only, regardless of before , after part, i've tried several patterns, not confident enough regex , can't seem find pattern works.

edit

• "tag :" aways present.

• the hexa part want extract has variable length

• what after user comment, anything

could ? in advance ! michael

assuming string there template, , assuming posix regular expression parser,

/^tag: ([0-9a-f]{8})/ 

should work. if length variable, change {8} {m,n}, m , n minimum , maximum possible number of characters can expect, respectively.