(gawk.info.gz) Library Functions

 
 A Library of `awk' Functions
 ****************************
 
     User-Defined Functions User-defined, 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 
 Practical `awk' Programs Sample 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.
 
     Extracting Programs from Texinfo Source Files Extract Program,
 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  How to Contribute How To Contribute, for
 more information.
 
    The programs in this major node and in  Practical `awk'
 Programs Sample Programs, freely use features that are `gawk'-specific.
 Rewriting these programs for different implementations of awk is pretty
 straightforward.
 
    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' ( Using `gawk''s `nextfile'
 Statement Nextfile Statement.)  to skip any remaining input in the
 input file.   Implementing `nextfile' as a Function Nextfile
 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
 use only 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.

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