Classic Shell Scripting

Chapter 4. Text Processing Tools

Some operations on text files are so widely applicable that standard tools for those tasks were developed early in the Unix work at Bell Labs. In this chapter, we look at the most important ones.

Sorting Text

Text files that contain independent records of data are often candidates for sorting. A predictable record order makes life easier for human users: book indexes, dictionaries, parts catalogs, and telephone directories have little value if they are unordered. Sorted records can also make programming easier and more efficient, as we will illustrate with the construction of an office directory in Chapter 5.

Like awk, cut, and join, sort views its input as a stream of records made up of fields of variable width, with records delimited by newline characters and fields delimited by whitespace or a user-specifiable single character.

sort

Usage

sort [ options ] [ file(s) ]

Purpose

Sort input lines into an order determined by the key field and datatype options, and the locale.

Major options

 

-b

Ignore leading whitespace.

-c

Check that input is correctly sorted. There is no output, but the exit code is nonzero if the input is not sorted.

-d

Dictionary order: only alphanumerics and whitespace are significant.

-g

General numeric value: compare fields as floating-point numbers. This works like -n, except that numbers may have decimal points and exponents (e.g., 6.022e+23). GNU version only.

-f

Fold letters implicitly to a common lettercase so that sorting is case-insensitive. ...