Unix Power Tools, 3rd Edition

Chapter 22. Sorting

Putting Things in Order

Summary Box

Sorting a file under Unix is easy, right? Of course it is, if all you want to do is sort a list of single words, or sort lines starting with the first character in the line. But if you want to do more than that, there’s a lot more to the sort command than typing sort filename:

• Section 22.2 describes how to select individual fields from a line for sort to operate on.

• Section 22.3 describes how to change the field delimiter from whitespace to some other character.

• Section 22.4 describes the kinds of problems that you can encounter if fields are delimited by whitespace.

• Section 22.5 clarifies the distinctions between alphabetic and numeric sorting.

• Section 22.6 gives miscellaneous hints about useful sort options.

But learning the mechanics of sort isn’t the end of the story. Like most of the other things you’ll find in the Unix toolbox, sort is even more powerful when it’s used with other programs. For example, you can:

• Sort paragraphs or other multiline entries.

• Sort lines by how long they are (Section 22.7).

• Sort a list of names by last name, whether or not there’s a middle name as well (Section 22.8).

— TOR

Sort Fields: How sort Sorts

Unless you tell it otherwise, sort divides each line into fields at whitespace (blanks or tabs), and sorts the lines by field, from left to right.

That is, it sorts on the basis of field 0 (leftmost), but when the leftmost fields are the same, it sorts on the basis of field 1, and so on. This is hard to put ...