Unix utility which sorts the lines of a file. Examples follow: 

$ cat phonebook

 Smith, Brett     555-4321
 Doe, John        555-1234
 Doe, Jane        555-3214
 Avery, Cory      555-4321
 Fogarty, Suzie   555-2314

 $ sort phonebook

 Avery, Cory      555-4321
 Doe, Jane        555-3214
 Doe, John        555-1234
 Fogarty, Suzie   555-2314
 Smith, Brett     555-4321

The -n option makes the program to sort according to numerical value: 

 $ du /bin/* | sort -n

 4       /bin/domainname
 4       /bin/echo
 4       /bin/hostname
 4       /bin/pwd
 ...
 24      /bin/ls
 30      /bin/ps
 44      /bin/ed
 54      /bin/rmail
 80      /bin/pax
 102     /bin/sh
 304     /bin/csh