Sort was part of Version 1 Unix and was originally written by Ken Thompson. By Version 4 Thompson had modified it to use pipes, but sort retained an option to name the output file because it was used to sort a file in place. In Version 5, Thompson invented "-" to represent standard input. The version of bundled in GNU coreutils was written by Mike Haertel and Paul Eggert. This implementation employs the merge sort algorithm. Similar commands are available on many other operating systems, for example a command is part of ASCII's MSX-DOS2 Tools for MSX-DOS version 2.
Syntax
sort ... ... With no FILE, or when FILE is -, the command reads from standard input.
$ catphonebook Smith, Brett 555-4321 Doe, John 555-1234 Doe, Jane 555-3214 Avery, Cory 555-4132 Fogarty, Suzie 555-2314 $ sortphonebook Avery, Cory 555-4132 Doe, Jane 555-3214 Doe, John 555-1234 Fogarty, Suzie 555-2314 Smith, Brett 555-4321
Sort by number
The -n option makes the program sort according to numerical value. The command produces output that starts with a number, the file size, so its output can be piped to to produce a list of files sorted by file size: $ du /bin/* | sort -n 4 /bin/domainname 24 /bin/ls 102 /bin/sh 304 /bin/csh
Columns or fields
Use the -k option to sort on a certain column. For example, use "-k 2" to sort on the second column. In old versions of sort, the +1 option made the program sort on the second column of data. This usage is deprecated. $ cat zipcode Adam 12345 Bob 34567 Joe 56789 Sam 45678 Wendy 23456
$ sort -k 2n zipcode Adam 12345 Wendy 23456 Bob 34567 Sam 45678 Joe 56789
Sort on multiple fields
The -k m,n option lets you sort on a key that is potentially composed of multiple fields : $ cat quota fred 2000 bob 1000 an 1000 chad 1000 don 1500 eric 500 $ sort -k2,2 -k1,1 quota eric 500 an 1000 bob 1000 chad 1000 don 1500 fred 2000 Here the first sort is done using column 2. -k2,2 specifies sorting on the key starting and ending with column 2. If -k2 is used instead, the sort key would begin at column 2 and extend to the end of the line, spanning all the fields in between. The n stands for 'numeric ordering'. -k1,1 dictates breaking ties using the value in column 1, sorting alphabetically by default. Note that bob, and chad have the same quota and are sorted alphabetically in the final output.
Sorting a file with tab separated values requires a tab character to be specified as the column delimiter. This illustration uses the shell's dollar-quote notation to specify the tab as a C escape sequence. $ sort -k2,2 -t $'\t' phonebook Doe, John 555-1234 Fogarty, Suzie 555-2314 Doe, Jane 555-3214 Avery, Cory 555-4132 Smith, Brett 555-4321
Sort in reverse
The -r option just reverses the order of the sort: $ sort -rk 2n zipcode Joe 56789 Sam 45678 Bob 34567 Wendy 23456 Adam 12345
Sort in random
The GNU implementation has a -R --random-sort option based on hashing; this is not a full random shuffle because it will sort identical lines together. A true random sort is provided by the Unix utility shuf.
Sort by version
The GNU implementation has a -V --version-sort option which is a natural sort of numbers within text. This happens to work for ip addresses.
