Find Command with Regex Quantifier {1,2}

sed -i -E "s/(<username>.+)name(.+<\/username>)/\1something\2/" file.xml

This is, I think, what you're looking for.

Explanation:

• parentheses in the first part define groups (strings in fact) that can be reused in the second part
• \1, \2, etc. in the second part are references to the i-th group captured in the first part (the numbering starts with 1)
• -E enables extended regular expressions (needed for + and grouping).

Finding with ls: first things first, ls | grep cisco is a bit verbose, since cisco isn't a regular expression. Try:

ls *cisco*

Using find: along the same lines, -regex is overkill with a simple, static pattern. How about:

find -name '*cisco*'

The quotes are required so the glob is interpreted by find, not the shell. Also, -print is required for many versions of find, but is optional (and the default predicate) for others (e.g. GNU find). Feel free to add it if you need it.

If you need to search for ‘cisco’ in the full pathname, you could try this:

find -path '*cisco*'

which is equivalent to find | fgrep cisco.

Using find with regular expressions: let's do that anyway, since this is what you want. Shamelessly copying from the GNU find manpage:

-regex pattern

          File  name  matches  regular  expression  pattern.  This is a match
          on the whole path, not a search.  For example, to match a file named
          `./fubar3', you can use the regular expression `.*bar.' or `.*b.*3',
          but not `f.*r3'.

What this means is that your regular expression is wrapped in an invisible ^...$, so it must match every character in the full pathname of the file. So, as nwildner and otokan said in the comments, you should use something like:

find -regex '.*cisco.*'

And you don't even need the -regextype for something this simple.