We'll start off with a simple one: write a program that reads a file of e-mail messages and then prompts the user for a message number. After each message number is input, the program prints the contents of the associated e-mail message and prompts for another message number, quitting when the user enters the character 'q' or indicates end-of-file. The name of the file to read is given on the command line.Here's an example session:
Your program should be calledcl readmbox mbox 6 messages read. message number: 1 Would you like to make money fast? message number: 7 message number 7 is out of range. Numbers 1 through 6 are valid message numbers. message number: q clreadmboxand should accept a single command line argument giving the name of the mailbox to read.
This project requires that you know about the formats of two entities: messages and mailboxes.Message Format
The message format used in this project is a simple form of the RFC 822 standard used for Internet mail transport.First, some definitions:
A message consists of a header followed by the contents. The header is separated from the contents by an empty text-line. The empty text-line separating a message's header and contents is not part of either the header or the contents.
- character
- any of the ASCII characters from NUL (0 decimal) to DEL (127 decimal) inclusive.
- linear white space character
- either of the characters space (
' ', ASCII character SP, 32 decimal) or tab ('\t', ASCII character HT, 9 decimal).- linear white space
- a non-empty sequence of linear white space characters.
- newline
- the character or characters that correspond to the newline character
'\n'in C++.- alphanumeric character
- an upper or lower case letter (
'A'through'Z'and'a'through'z'), a decimal digit ('0'through'9', or one of the characters hyphen'-'or underscore'_'.- word
- a non-empty sequence of alphanumeric characters starting with an upper- or lower-case letter.
- text-line
- a possibly empty sequence of characters, none of which are the newline character, followed by a newline.
- empty text-line
- an empty sequence of characters followed by a newline. Note that a text-line containing linear white space is not an empty text-line because it contains a non-empty sequence of characters.
RFC 822 doesn't define the format of a messages contents, and this project won't either, except to assume that the contents is a possibly empty sequence of text-lines.
A message header is a non-empty sequence of fields. Each field is a text-string of the form
word:text-lineThe word before the colon is called the label.Mailbox Format
A mailbox is a possibly empty sequence of messages. Each message is preceded by a text-line of the formFrom text-lineNote the linear white space between "From" and the text-line. Messages are separated from one another by at least one empty text-line.Here is an example mailbox you may use to test your program.
This page last modified on 4 July 2000.