Search for all files modified in the last N days containing a specific text in their name
find DIR -mtime -N -name "*TEXT*"
find ~ -mtime -5 -name "*log*"
Will display all the files modified in the past 5 days which include the text 'log' in their filename.
Determine which processes use the most memory
ps aux | sort -nk 4 | tail
Will show the first 10 processes which use the most memory, using ascendant sorting. Alternately:
ps aux | sort -nrk 4 | head
Will show the first 10 processes using most memory, using descendent sorting.
Output of ps aux | sort -nrk 4 | head
Display the username which is currently logged in
Show date using format modifiers
Will output time in format HOUR:MINUTE:SECOND. You can use any format specifiers explained in the man page. The double quotes are required in case you need to use spaces.
Showing date in format month, day year
Show info about a specific user
Output of finger $USER
Show disk usage separately for each partition
The -h switch will tell df to show human-readable sizes (KB, MB and GB when it is the case)
df -B 1K
Will show sizes in kilobytes.
Show which modules are loaded
Add or remove a module to/from the Linux kernel
Insert a module:
Remove a module:
modprobe -r MODULE
Search for a file using locate
Will search the locate database (created with updatedb) for any path or file which contains FILENAME.
Change the encoding of a text file
iconv -f INITIAL_ENCODING -t DESIRED_ENCODING filename
iconv -f ISO-8859-16 -t UTF-8 myfile.txt
Will change the encoding of myfile.txt from ISO-8859-16 (Romanian) to UTF-8.