Systems Programming Assignment 3: awk Solution

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






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



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






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










Assignment 3: awk Page 1 of 4
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.























































Assignment 3: awk Page 2 of 4
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



User : zeh458



13
vim prog . c
14





Earliest Start Time :



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







17




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










Assignment 3: awk Page 3 of 4
$ 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