Sort

By default, sorts file rows using the first field as key, assuming fields are separated by white space.

To sort in reverse numerical order:

sort -nr <file>

To sort on first two fields using : as delimeter:

sort -t: +0 -2 <file>

To sort on characters 20-25:

sort +0.20 -.25 <file>

To merge file1 and file2:

sort -m <file1> <file2>

To merge file 1 with the output of ls:

ls | sort -m file1 -

To sort the password file by id:

sort -t: -k3 -n /etc/passwd

To extract usernames (play with the head and tail):

sort -t: -k3 -n /etc/passwd | tail -18 | head -17 | awk -F: '{print $1}'

To shuffle lines randomly:

sort -R myfile.txt

To sort IP addresses:

sort -t. -k1,1n -k2,2n -k3,3n -k4,4n myfile.txt