Commands worth knowing by shape.
FINDING THE LARGEST DIRECTORIES
Summarise usage one level deep, sort numerically, take the top few.
FINDING RECENTLY CHANGED FILES
find with a modification time restriction, on a specific path.
COUNTING REQUESTS PER ADDRESS IN A LOG
Extract the first field, sort, count unique, sort by count.
FINDING THE BUSIEST REQUESTED PATHS
Extract the request field, then the same counting pattern.
WATCHING A LOG FOR A SPECIFIC TERM
Follow the file and filter it.
FINDING WHAT HOLDS A PORT
List listening sockets with process names.
FINDING WHAT IS FILLING A DISK RIGHT NOW
Interactive disk usage, or repeated usage summaries.
SEARCHING WEB FILES FOR A STRING
Recursive search restricted to the document root, listing filenames only.
COUNTING FILES IN A DIRECTORY
List and count lines, being aware of hidden files.
CHANGING PERMISSIONS ON FILES BUT NOT DIRECTORIES
find with a type restriction and the execute option.
REPLACING TEXT ACROSS MANY FILES
find the files, confirm the list, then apply a substitution with a backup.
CHECKING A CERTIFICATE'S EXPIRY REMOTELY
Connect and read the dates.
COMPARING TWO DIRECTORIES
rsync with a dry run.
WHAT TO DO WITH ANY OF THESE
Read it before running it, and check the path.
