File links can contain additional information to make Emacs jump to a particular location in the file when following a link. This can be a line number or a search option after a double1 colon. For example, when the command C-c l creates a link (see Handling links) to a file, it encodes the words in the current line as a search string that can be used to find this line back later when following the link with C-c C-o.
Here is the syntax of the different ways to attach a search to a file link, together with an explanation:
[[file:~/code/main.c::255]] [[file:~/xx.org::My Target]] [[file:~/xx.org::*My Target]] [[file:~/xx.org::#my-custom-id]] [[file:~/xx.org::/regexp/]]
regexp. This uses the Emacs command
occurto list all matches in a separate window. If the target file is in Org mode,
org-occuris used to create a sparse tree with the matches.
As a degenerate case, a file link with an empty file name can be used
to search the current file. For example,
[[file:::find me]] does
a search for ‘find me’ in the current file, just as
‘[[find me]]’ would.
 For backward compatibility, line numbers can also follow a single colon.