CSc 3320: Homework # 1 solved

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Answer the following questions briefly. Provide clear and succinct
Points per question = 5
1. Tell the differences between Unix and Linux. Then please list some
operating systems (at least three) which belong to Unix but not Linux.
2. What is the pipe mechanism in UNIX? And show one command using pipe
and explain how the pipe works in it?
3. In a Linux system, you can issue the command ls / to check the sub
directories under root. Please describe the meanings of directory /bin, /dev,
/boot, /usr, /etc, /mnt, /sbin, /var separately. For example, you can say that
/bin contains binary executable files.
4. What is the meaning of Multitask and Multi-user in a Unix system?
5. What does -rwxr-xr-x mean in terms of permissions for a file? What is the
exact unix command (with the octal representation) for changing the
permissions to this setting?
6. In class, you have learned the meaning of read, write and execute
permission for regular files. However, these permissions are also applied to
directories. So please describe the meaning of read, write, and execute
permission for directory.
Part II-a
Regular Expression
Find outcomes for each given basic/extended regular expression
(maybe multiple correct answers)
Points per question: 2.5
‘ab+a’ (extended regex)
Answer: aba , abba ; Pattern : The matched string should begin and end
with ‘a’ and ‘b’ occurs at least once between leading and ending ‘a’)
Note: 7) to 10) are basic regexes; Note: 11) to 18) are extended regexes.
7) ‘a[ab]*a’
8) ‘a(bc)?’
9) ‘.[ind]*’
10) ‘[a-z]+[a-z]’
11) ‘[a-z] (\+[a-z])+’
12) ‘a.[bc]+’
13) ‘a.[0-9]’
14) ‘[a-z]+[\.\?!]’
15) ‘[a-z]+[\.\?!]\s*[A-Z]’
16) ‘(very )+(cool )?(good|bad) weather’
17) ‘-?[0-9]+’
18) ‘-?[0-9]*\.?[0-9]*’
Part II-b
Regular Expression
Write down the extended regular expression for following questions.
E.g. Social security number in the format of 999-99-9999. Answer:
Points per question: 5
19) Valid URL beginning with “http://” and ending with “.edu” (e.g.,
20) Non-negative integers. (e.g. 0, +1, 3320)
21) A valid absolute pathname in Unix (e.g. /home/ylong4, /test/try.c)
22) Identifiers which can be between 1 and 10 characters long, must
start with a letter or an underscore. The following characters can be
letters or underscores or digits. (e.g. number, _name1, isOK).
23) Phone number in any of the following format: 9999999999,999-999-
9999, (999)-999-9999. (Note: all of these formats should be matched by a
single regular expression)
Part III
Points per question: 15
24. Create a file named homework_instructions.txt using VI editor and type in
it all the submission instructions from page1 of this document. Save the file in
a directory named homeworks that you would have created. Set the
permissions for this file such that only you can edit the file while anybody can
only read. Find and list (on the command prompt) all the statements that
contain the word POINTS. Submit your answer as a description of what you did
in a sequential manner (e.g. Step1 … Step 2… and so on..). Add a screenshot to
your answer as a proof of evidence.