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(gawk.info)Library Functions

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A Library of `awk' Functions
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   Note: User-Defined Functions, describes how to write
your own `awk' functions.  Writing functions is important, because it
allows you to encapsulate algorithms and program tasks in a single
place.  It simplifies programming, making program development more
manageable, and making programs more readable.

   One valuable way to learn a new programming language is to _read_
programs in that language.  To that end, this major node and Note:
Practical `awk' Programs, provide a good-sized body of
code for you to read, and hopefully, to learn from.

   This major node presents a library of useful `awk' functions.  Many
of the sample programs presented later in this Info file use these
functions.  The functions are presented here in a progression from
simple to complex.

   Note: Extracting Programs from Texinfo Source Files,
presents a program that you can use to extract the source code for
these example library functions and programs from the Texinfo source
for this Info file.  (This has already been done as part of the `gawk'
distribution.)

   If you have written one or more useful, general purpose `awk'
functions and would like to contribute them to the author's collection
of `awk' programs, see Note: How to Contribute, for
more information.

   The programs in this major node and in Note: Practical `awk'
Programs, freely use features that are `gawk'-specific.
It is straightforward to rewrite these programs for different
implementations of `awk'.

   Diagnostic error messages are sent to `/dev/stderr'.  Use `| "cat
1>&2"' instead of `> "/dev/stderr"', if your system does not have a
`/dev/stderr' or if you cannot use `gawk'.

   A number of programs use `nextfile' (Note: Using `gawk''s `nextfile'
Statement.)  to skip any remaining input in the
input file.  Note: Implementing `nextfile' as a Function,
 shows you how to write a function that does the same thing.

   Finally, some of the programs choose to ignore upper- and lowercase
distinctions in their input. They do so by assigning one to
`IGNORECASE'.  You can achieve almost the same effect(1) by adding the
following rule to the beginning of the program:

     # ignore case
     { $0 = tolower($0) }

Also, verify that all regexp and string constants used in comparisons
only use lowercase letters.

Library Names

How to best name private global variables in

library functions.

General Functions

Functions that are of general use.

Data File Management

Functions for managing command-line data

files.

Getopt Function

A function for processing command-line

arguments.

Passwd Functions

Functions for getting user information.

Group Functions

Functions for getting group information.

   ---------- Footnotes ----------

   (1) The effects are not identical.  Output of the transformed record
will be in all lowercase, while `IGNORECASE' preserves the original
contents of the input record.