Itx8071-task1

This homework assignment requires the knowledge from Module 3.

Please write a regular expression for matching the sequence of software module names and optional version numbers, so that the sequence will follow these rules:

1) The sequence consists of one or more parts. If there are two or more parts, they are separated with a comma (",") character.

2) Each part of the sequence is a software module name which is optionally followed by a version number. If the version number is present, there must be a dash ("-") character between the software module name and the version number. If there is no version number, the use of dash character after the software module name is not permitted.

3) Software module name must contain at least one character and must begin with a letter, and may contain letters and digits only.

4) The version number consists of one or more elements. If there are two or more version number elements, these elements must be separated with a dot (".") character. Note that the dot character may not appear before the first or after the last element. Each version number element must be a sequence of one or more digits which may be optionally followed by one letter.

Please note that for accomplishing the task, one regular expression has to be submitted which is suitable for use with the egrep or pcregrep tool. It is not acceptable to submit the solution in a fragmented way (e.g., several isolated expressions for addressing different parts of the task). Also, it is not allowed to submit programs in Java, Python, Perl (or any other language) for the solution. Finally, if the solution only works with the examples provided below but does NOT meet the task specification, it will be treated as incorrect.

Examples of sequences the regular expression must match:

m4-1.4.16
(the sequence has one valid part -- a software module name with a version number of 3 elements) 

coreutils,pcre-8.32
(the sequence has two valid parts -- note that the first part does not have a version number) 

libtasn1-4.09a,GeoIP-1.5.0,iwl6000g2a
(the sequence has three valid parts, with the first and second parts having version numbers) 

iwl2030,lz4,mydatabase-13i.222.5b,e2fsprogs,PyYAML
(the sequence has five valid parts, where only the third part has a version number) 

Examples of sequences the regular expression must NOT match:

coreutils, pcre-8.32
(the second part begins with a space character which is illegal) 

coreutils 8.22,pcre--8.32
(the first part contains a space character which is illegal; also, in the second part the software module name and version number are separated by two dash characters which is illegal) 

m4-1.4.16,
(the first part ends with comma, but there is no following second part) 

my_db
(the software module name contains an illegal character _) 

mydb-11A3.1
(the first version number element contains a character A, but A is not the last character of the version number element) 

mydb-11..2
(version number contains two dots, but there is no version number element between them) 

mydb-
(software module name is followed by -, but there is no version number) 

mydb-12ab.1
(the first version number element ends with more than one letter which is illegal)

mydb,,mydaemon
(the second part of the sequence is empty) 

!"libtasn1-4.09a,GeoIP-1.5.0,iwl6000g2a
(the sequence begins with illegal characters) 

coreutils-8.22,pcre-8.32+%
(the sequence ends with illegal characters)