Systems Programming Assignment 3: awk Solution

Description

Part A

For this part of the assignment, you will create a single command which will take the contents of a passwd file (usually found in /etc/passwd) and print it in sorted order by the user’s last name (that is, their surname, not their username). Normally, you could solve this with the following options on

sort: $ sort -t: -k6 /path/to/passwd

You, however, must solve this problem with the utilities covered in class so far. You may (and should) use sort, but you may not use any of its options (e.g., -k, -t, etc).

Example

Input:

1	lkj293 : x : 1 5 3 9 : 1 5 4 3		: Albert		Einstein :/ home / einstein :/ bin / bash
2	kkr590 : x : 1 5 4 0 : 1 5 4 4		: Elvis		Presley :/ home / presley :/ bin / bash
3	nwk409 : x : 1 5 4 1 : 1 5 4 5		: George		W a s h i n g t o n :/ home / w a s h i n g t o n :/ bin / bash
4	yaa265 : x : 1 5 4 2 : 1 5 4 6		: Bruce		Banner :/ home / banner :/ bin / bash
5	yhn211 : x : 1 5 4 3 : 1 5 4 7		: George		Harrison :/ home / harrison :/ bin / bash
6	lfa806 : x : 1 5 4 4	:1548	: Jane	Austen :/ home / austen :/ bin / bash
7	ilo709 : x : 1 5 4 5	:1549	: Walt	Disney :/ home / disney :/ bin / bash
8	rfd576 : x : 1 5 4 6	:1550	: Buzz	Aldrin :/ home / aldrin :/ bin / bash
9	lko889 : x : 1 5 4 7	:1551	: Marie		Curie :/ home / curie :/ bin / bash

10. cfq219 : x : 1 5 4 8 : 1 5 5 2 : J . R . R . Tolkien :/ home / tolkien :/ bin / bash

10. ncz856 : x : 1 5 4 9 : 1 5 5 3 : C h r i s t o p h e r Columbus :/ home / columbus :/ bin / bash

12 pql747 : x : 1 5 5 0 : 1 5 5 4 : Julius Caesar :/ home / caesar :/ bin / bash

Output:

1	rfd576 : x : 1 5 4 6	:1550	: Buzz	Aldrin :/ home / aldrin :/ bin / bash
2	lfa806 : x : 1 5 4 4	:1548	: Jane	Austen :/ home / austen :/ bin / bash
3	yaa265 : x : 1 5 4 2	:1546	: Bruce	Banner :/ home / banner :/ bin / bash
4	pql747 : x : 1 5 5 0	:1554	: Julius Caesar :/ home / caesar :/ bin / bash

• ncz856 : x : 1 5 4 9 : 1 5 5 3 : C h r i s t o p h e r Columbus :/ home / columbus :/ bin / bash

6	lko889 : x : 1 5 4 7 : 1 5 5 1		: Marie	Curie :/ home / curie :/ bin / bash
7	ilo709 : x : 1 5 4 5	:1549	: Walt Disney :/ home / disney :/ bin / bash
8	lkj293 : x : 1 5 3 9	:1543	: Albert	Einstein :/ home / einstein :/ bin / bash
9	yhn211 : x : 1 5 4 3	:1547	: George	Harrison :/ home / harrison :/ bin / bash
10	kkr590 : x : 1 5 4 0	:1544	: Elvis	Presley :/ home / presley :/ bin / bash

11. cfq219 : x : 1 5 4 8 : 1 5 5 2 : J . R . R . Tolkien :/ home / tolkien :/ bin / bash

12 nwk409 : x : 1 5 4 1 : 1 5 4 5 : George W a s h i n g t o n :/ home / w a s h i n g t o n :/ bin / bash

Script Execution (Part A)

Since the fox machines do not have useful /etc/passwd files (no first and last names), you will use the one provided with this assignment. Your submission will include a bash file (assign3A.sh) with exactly one line in it (you do not need a shebang) and should take the path to the passwd file as the first argument. Do not include an awk file or any other files besides assign3A.sh.

$ assign3A.sh /path/to/passwd

Part B

For this part of the assignment, you will only use the utilities covered in class so far (primarily awk) to create a program for printing user process information. Do not use Python or any programs/utilities not covered in class.

Your program should take the output from ps -ef and print the following for each user having a username matching the abc123 format:

• Username

• List of commands

After listing statistics for each user, the program should print the following information for all users having a username matching the abc123 format:

• Line with earliest start time

• Line with latest start time

Do not use sed, Python, or any other languages/utilities not covered in class.

Example

The example below is an excerpt from the ps -ef command which your program should be able to take as input. Note that if a process began execution on a previous calendar day, its STIME value will not be in the usual “hours and minutes” format, but rather in “month and day” format. This should be accounted for properly, and thus a simple text/numerical comparison will not suffice.

Input:

1	UID	PID	PPID	C	STIME	TTY	TIME	CMD
2	adz110	5344	5334	0	08:47	pts /2	00:00:00	bash
3	dmq292	6908	6854	0	Jun04	pts /1	00:00:00	bash
4	adz110	7227	7150	0	Jul11	pts /9	00:00:00	who
5	erg474	7466	7461	0	08:54	pts /10	00:00:00	ls
6	dmq292	7966	7960	0	Jun04	pts /13	00:00:00 assign1 . sh if of
7
	xle135	8983	8636	0	08:59	pts /15	00:00:00	ssh ctf . cs . utsarr . net
8	zeh458	9057	1980	0	08:59	pts /7	00:00:00	vim	prog . c
9	rslavin	9150	9139	0	08:59	pts /16	00:00:00	ps	– af
10	xle135	8636	8628	0	08:58	pts /15	00:00:00	bash

Output:

• User : adz110

2	bash
3	who

• User : dmq292

5	bash
6	assign1 . sh if of

• User : erg474

8 ls

• User : xle135

10	bash
11	ssh ctf . cs . utsarr . net

12. User : zeh458

13	vim prog . c
14

15. Earliest Start Time :

16 dmq292 6908 6854 0 Jun04 pts /1 00:00:00 bash

17

18. Latest Start Time :

19 xle135 8983 8636 0 08:59 pts /15 00:00:00 ssh ctf . cs . utsarr . net

Also, if there is a tie for earliest or latest start times, take the one with the UID that comes first alphabetically.

Hint: Consider using sort to help with grouping.

Script Execution (Part B)

Your program should each be invoked through a single bash file (see below) with input taken from stdin. The resulting output should be printed directly to stdout.

• assign3B.sh < ps.in

or

$ ps -ef | assign3B.sh

Assignment Data

Sample input files can be found in:

/usr/local/courses/ssilvestro/cs3423/Fall19/assign3.

Script Files

Your submission should consist of multiple files:

• assign3A.sh – a bash script with a single line of code (i.e., one command) for part A

• assign3B.sh – a bash script to invoke for part B.

• assign3B.awk – the awk program used in assign3B.awk

Verifying Your Programs

Part A can be tested with the sample input provided with passwd.in.

Part B can be tested with the sample input provided with ps.in. Your program should also work with arbitrary input from the ps -ef command.

Submission

Turn your assignment in via Blackboard. Your zip file, named abc123.zip with your personal abc123 should contain only your bash and awk files.

Assignment 3: awk Page 4 of 4