sed & awk, 2nd Edition

Information Retrieval

An awk program can be used to retrieve information from a database, the database basically being any kind of text file. The more structured the text file, the easier it is to work with, although the structure might be no more than a line consisting of individual words.

The list of acronyms below is a simple database.

$ cat acronyms
BASIC	Beginner's All-Purpose Symbolic Instruction Code
CICS	Customer Information Control System
COBOL	Common Business Oriented Language
DBMS	Data Base Management System
GIGO	Garbage In, Garbage Out
GIRL 	Generalized Information Retrieval Language

A tab is used as the field separator. We’re going to look at a program that takes an acronym as input and displays the appropriate line from the database as output. (In the next chapter, we’re going to look at two other programs that use the acronym database. One program reads the list of acronyms and then finds occurrences of these acronyms in another file. The other program locates the first occurrence of these acronyms in a text file and inserts the description of the acronym.)

The shell script that we develop is named acro. It takes the first argument from the command line (the name of the acronym) and passes it to the awk script. The acro script follows:

$ cat acro
#! /bin/sh
# assign shell's $1 to awk search variable
awk '$1 == search' search=$1 acronyms

The first argument specified on the shell command line ($1) is assigned to the variable named search; this variable is passed as a parameter ...