From the Classroom Whiteboard/ChalkboardIndex
Your in-class notes go here.
- is this directory empty?
ls
- copying and moving files into existing directories:
- A tool for explaining shell command lines – explainshell
- does not differentiate between
ps Unix and BSD options correctly
For BASH built-in commands, try the help command, e.g. help pwd, help help, help echo, etc.
Explain what is happening in this simple find shell command line:
$ mkdir a
$ touch a/bob a/bling a/boor a/blue a/bubba
$ find a -name b* # 1. output: five lines (correct)
a/bubba
a/blue
a/boor
a/bling
a/bob
$ touch b
$ find a -name b* # 2. output: zero lines - why not five?
$ touch blue
$ find a -name b* # 3. output: error message - why not five lines?
find: paths must precede expression: blue
$ rm b
$ find a -name b* # 4. output: one line - why not five?
a/blue
$
- Explain exactly why the same
find command, run four times on the same directory, gives four very different outputs.
- How would you fix the command to always give the correct (first) output? Answer
Preliminary CentOS checkingIndex
The checking program is still being written. Here’s what you can do so far:
On the CLS, create your assignment07 directory in the usual place. Then log in to your CenOS machine (as root) and run these three commands on your CentOS machine, replacing abcd0001 with your own CLS userid in the third one:
# cd /tmp
# curl -A mozilla http://teaching.idallen.com/cst8207/13f/notes/data/assignment07do.sh >do.sh
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
112 560 112 560 0 0 9433 0 --:--:-- --:--:-- --:--:-- 1931
# USER=abcd0001 sh do.sh
---------------------------------------------------------------------------
abcd0001: FETCH version 2. Connecting to CLS as USER='abcd0001' using ssh
---------------------------------------------------------------------------
abcd0001: Use local Algonquin IP cst8207-alg.idallen.ca [y/N]? y
abcd0001: Please wait; using ssh to connect to user 'abcd0001' on cst8207-alg.idallen.ca ...
abcd0001@cst8207-alg.idallen.ca's password:
*** COURSE LINUX SERVER ***
---------------------------------------------------------------------------
idallen-ubuntu assignment07fetch_server.sh version 4 run by abcd0001.
Please wait; collecting info from abcd0001 Virtual Machine
---------------------------------------------------------------------------
VM files collected into CST8207-13F/Assignments/assignment07/abcd0001.tar.bz on CLS.
Now running checking program for abcd0001 on CLS:
----------------------------------------------------------------------------
check: idallen-ubuntu Fri Oct 18 12:48:40 2013
check: CST8207 assignment07 check program version 37
*** Checking account for abcd0001 on idallen-ubuntu ***
Going into HOME directory /home/abcd0001 on idallen-ubuntu
GOOD(2): Found correct 'source' statement in .bash_profile
GOOD(2): Found non-interactive return first line in .bashrc
GOOD(1): Found PS1= line in .bashrc
Going into directory CST8207-13F/Assignments/assignment07 on idallen-ubuntu
*** 4.? CLS: Set Up Tasks in assignment07 on idallen-ubuntu ***
On idallen-ubuntu: Using abcd0001.tar.bz dated Fri Oct 18 12:48:40 2013
Checking 'abcd0001.tar.bz' version 4 created Fri Oct 18 12:48:40 EDT 2013
*** 4.? CentOS 6.4 Installation Verify ***
GOOD(2): Found correct hostname
NOTE: Found correct kernel running
GOOD(2): Found correct number of RPM packages (201)
GOOD(2): Found correct memory size
GOOD(2): Found correct Toronto time zone
*** 4.? CentOS 6.4: Grub menu and time-out ***
GOOD(2): Found correct time out line in CentOS 6.4 grub.conf
GOOD(2): Found correct hidden menu line in CentOS 6.4 grub.conf
*** All Done ***
WARNING: Cannot find submission file 'assignment07.txt' on CLS
----------------------------------------------------------------------------
*** CHECK SCRIPT NOT FINISHED YET - SOON ***
----------------------------------------------------------------------------
Real Sysadmin WorkIndex
Find Identical FilesIndex
I needed to find all files named similarly to save.sh and see which ones had the same content. The sum command produces a unique number based on content, so I used:
$ find ../.. -name '*save*.sh' | xargs sum | sort
[...]
00153 1 ../../net2003/07w/t3unx/multi/save.sh
00153 1 ../../net2003/08w/t1unx/save.sh
00153 1 ../../net2003/08w/t2unx/save.sh
00153 1 ../../net2003/08w/t3unx/multi/save.sh
13967 1 ../../dat2333/00f/t4unx/save-file.sh
17009 1 ../../dat2343/00f/proj3/saveproj3.sh
17009 1 ../../dat2343/01f/proj3/saveproj3.sh
40014 1 ../../dat2333/00f/save-file.sh
40014 1 ../../dat2333/99f/oak1/save-file.sh
40014 1 ../../dat2333/99f/save-file.sh
51494 1 ../../net2003/05w/dosave.sh
64071 1 ../../dat2330/04f/dosave.sh
The sums at the start of each line tell me which files have the same content. I can make sure these files are hard links to each other, rather than separate copies of the identical content.
Compare Scanner SheetsIndex
I ran your scanner sheets through ITS a second time. I couldn’t simply run a difference of the two files, because the first three fields on each line were different. Below is the command line that strips the first three fields from each file using sed with regular expressions, sorts the files to make sure they are in the same order, and compares them with the meld graphical difference program. The line uses BASH named pipes (FIFOs) syntax to name the two arguments to meld:
$ meld <(sed -e 's/^[^ ]* *[^ ]* *[^ ]* *N //' "$file1" | sort) \
<(sed -e 's/^[^ ]* *[^ ]* *[^ ]* *N //' "$file2" | sort)
The result was:
- One name got a missing letter scanned the second time. (This was the student who alerted me to the scanner problem.)
- A second name got an extra letter scanned (not part of the name).
- Six student numbers changed. Some got more digits; some fewer. (I ignore these. You were told not to put your student numbers on the sheets.)
None of the 46 test score fields changed in any of the sheets.
You will learn Regular Expressions next term in GNU/Linux II.
Author:
| Ian! D. Allen - idallen@idallen.ca - Ottawa, Ontario, Canada
| Home Page: http://idallen.com/ Contact Improv: http://contactimprov.ca/
| College professor (Free/Libre GNU+Linux) at: http://teaching.idallen.com/
| Defend digital freedom: http://eff.org/ and have fun: http://fools.ca/
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