find is a command line utility that will let you find files and then run commands on them. find also works well with piping filenames to xargs to process.

-- find all markdown files and list attributes
find . -name '*.md' -exec ls -l {} +
find . -name '*.md' | xargs ls -l

-- find all files (except markdown)
find . \! -name '*.md' -print


-- find directories
find . -type d
-- find files
find . -type f
-- find symbolic links
find . -type l


-- find files created less than 2 minutes ago
find . -newerBt '2 minutes ago'
-- find files changed less than 15 minutes ago
find . -newerct '15 minutes ago'
-- find files modified less than 30 minutes ago
find . -newermt '30 minutes ago'
-- find files last accessed less than 1 hour ago
find . -newerat '1 hour ago'

-- find files modified more recently than main.c
find . -newermm main.c
find . -newer main.c