Get only matching words using Grep in a command Linux, Shell command

We can use Grep to get the fields or string which contains the specified character, word or string.

cat filename|grep -oh "\w*@\w*"

so suppose a test file contains:

2017-06-19 01:04:49 trigproc man-db:amd64 2.7.5-1 <none>
2017-06-19 01:04:49 status half-configured man-db:amd64 2.7.5-1
2017-06-19 01:04:50 status installed man-db:amd64 2.7.5-1
2017-06-19 01:04:50 configure vim-runtime:all 2:8.0.0095-1ubuntu3 <none>
2017-06-19 01:04:50 status unpacked vim-runtime:all 2:8.0.0095-1ubuntu3
2017-06-19 01:04:50 status half-configured vim-runtime:all 2:8.0.0095-1ubuntu3
2017-06-19 01:04:51 status installed vim-runtime:all 2:8.0.0095-1ubuntu3
2017-06-19 01:04:51 trigproc gnome-menus:amd64 3.13.3-6ubuntu4 <none>
2017-06-19 01:04:51 status half-configured gnome-menus:amd64 3.13.3-6ubuntu4
2017-06-19 01:04:51 status installed gnome-menus:amd64 3.13.3-6ubuntu4
2017-06-19 01:04:51 trigproc hicolor-icon-theme:all 0.15-1 <none>
2017-06-19 01:04:51 status half-configured hicolor-icon-theme:all 0.15-1
2017-06-19 01:04:51 status installed vim-common:all 2:8.0.0095-1ubuntu3
2017-06-19 01:04:51 status installed hicolor-icon-theme:all 0.15-1
2017-06-19 01:04:51 configure vim-tiny:amd64 2:8.0.0095-1ubuntu3 <none>
2017-06-19 01:04:51 status unpacked vim-tiny:amd64 2:8.0.0095-1ubuntu3
2017-06-19 01:04:51 status unpacked vim-tiny:amd64 2:8.0.0095-1ubuntu3
2017-06-19 01:04:51 status half-configured vim-tiny:amd64 2:8.0.0095-1ubuntu3
2017-06-19 01:04:51 status installed vim-tiny:amd64 2:8.0.0095-1ubuntu3
2017-06-19 01:04:51 configure vim:amd64 2:8.0.0095-1ubuntu3 <none>
2017-06-19 01:04:51 status unpacked vim:amd64 2:8.0.0095-1ubuntu3
2017-06-19 01:04:51 status half-configured vim:amd64 2:8.0.0095-1ubuntu3
2017-06-19 01:04:51 status installed vim:amd64 2:8.0.0095-1ubuntu3

in a file /tmp/test then if we want to get all word with ubun we can give the command as

grep -oh "\w*ubun\w*" /tmp/test

will give this word from all lines.