Description

The ID3 tag format for MP3s and other multimedia files adds metadata describing the file. The contents of an ID3 tag are the following:

Offset	length	description
0	3	"TAG" identifier string.
3	30	Song title string.
33	30	Artist string.
63	30	Album string.
93	4	Year string.
97	28	Comment string.
125	1	Zero byte separator.
126	1	Track number byte.
127	1	Genre identifier byte.

An ID3 (v1.1) tag like above is appended to a file as the last 128 bytes. The tag is present if at the -128 from end offset there are the three ASCII characters TAG.

What To Do

For your project you will make a utility that can print the contents of an existing tag, if there, and add or modify a tag.

Make a program called id3tagEd and make it so that it runs with the following command line options:

id3tagEd FILENAME

should print the contents of the ID3 tag to the console if present, or give a message if not present

id3tagEd FILENAME -FIELD VALUE

should set the specified field to the value that follows it.

You should handle the following field names:

· Title

· Artist

· Album

· Year

· Comment

· Track

Make sure you are able to handle multiple {field, value} pairs on the command line at once. If the tag already exists in the specified file, then edit it, if not create a new tag by appending a tag at the end with the specified fields populated. Assume all others are to be empty (filled with 0s.)

The Submission

When you’re done, create a gzipped tarball of your source and compiled shell executable and copy them to:

~jrmst106/submit/449/

Make sure you name the file with your username, and that you have your name in the comments of your source file.

Note that this directory is insert-only, you may not delete or modify your submissions once in the directory. If you’ve made a mistake before the deadline, resubmit with a number suffix like abc123_1.tar.gz

The highest numbered file before the deadline will be the one that is graded, however for simplicity, please make sure you’ve done all the work and included all necessary files before you submit.