Documented in Volume 1 of the UNIX Programmers Manual.
% ls -Ralg | egrep ' xcd | xby ' will list names of files associated with a ANIs xdc or xby.
% ls -Ralg | egrep -v ' user | staff ' will list names of files associated with ANIs other than the primary ANI. Here, egrep is selecting all lines which do not (-v) contain the strings ' user ' or ' staff '.
See also grep.
To Index