Page:AWK Language Programming.pdf/9



If you are like many computer users, you would frequently like to make changes in various text files wherever certain patterns appear, or extract data from parts of certain lines while discarding the rest. To write a program to do this in a language such as C or Pascal is a time-consuming inconvenience that may take many lines of code. The job may be easier with.

The utility interprets a special-purpose programming language that makes it possible to handle simple data-reformatting jobs with just a few lines of code.

The GNU implementation of awk is called ; it is fully upward compatible with the System V Release 4 version of awk. is also upward compatible with the POSIX specification of the awk language. This means that all properly written awk programs should work with. Thus, we usually don't distinguish between and other awk implementations.

Using you can:


 * manage small, personal databases
 * generate reports
 * validate data
 * produce indexes, and perform other document preparation tasks
 * even experiment with algorithms that can be adapted later to other computer languages

1.1

The term refers to a particular program, and to the language that you use to tell this program what to do. When we need to be careful, we call the program "the utility" and the language "the  language." The term refers to a version of  developed as part of the GNU project. The purpose of this book is to explain both the language and how to run the  utility.

The main purpose of the book is to explain the features of, as defined in the POSIX standard. It does so in the context of one particular implementation,. While doing so, it will also attempt to describe important differences between and other  implementations. Finally, any features that are not in the POSIX standard for  will be noted.

This book has the difficult task of being both tutorial and reference. If you are a novice, feel free to skip over details that seem too complex. You should also ignore the many cross references; they are for the expert user, and for the on-line Info version of the document.