Alternative commands wtf?

nobodythere

I have a UNIX exam tomorrow. There's questions on past papers that go like this:

Give TWO alternative command line instructions to implement the following:
a) chmod u=rwx,g=rx,o-rwx <filename>
b) cd $HOME
c) cat readme.txt | grep unix | wc -l
d) mkdir "A directory name with spaces!"


To me these are fairly basic commands and I have no idea how I could implement them any other way... any ideas?

velocirafter

is (b) cd ~

I'm working on a windows machine at the moment so I'm not sure about that

cooperla

For c) I'd say you could just grep the file directly instead of cat'ing it first.

cooperla

... And for a) you could specify the numbers instead of rwx (i.e. chmod 757 filename).

warrenaldo

a) chmod 757 <filename>

Orion

a) chmod 750 <filename>
b) cd ~
c) grep -o <string> <filename> | wc -l
d) mkdir a\ directory\ name\ with\ spaces/

Orion

warrenaldo wrote: »

a) chmod 757 <filename>

It's 750 (+rwx,+rx,-rwx) ... unless the - is a typo of course. Or I could be confusing it with VMS

ethernet

grasshopa wrote: »

I have a UNIX exam tomorrow. There's questions on past papers that go like this:

Give TWO alternative command line instructions to implement the following:
a) chmod u=rwx,g=rx,o-rwx <filename>
b) cd $HOME
c) cat readme.txt | grep unix | wc -l
d) mkdir "A directory name with spaces!"


To me these are fairly basic commands and I have no idea how I could implement them any other way... any ideas?

1. chmod 757 filename
2. cd ~ OR cd /home/me
3. grep unix < readme.txt | wc -l
4. mkdir new\ dir

Even thought I think you're sitting a few seats away from me in this lab I was too lazy to get up!

Orion

Macros42 wrote: »

It's 750 (+rwx,+rx,-rwx) ... unless the - is a typo of course. Or I could be confusing it with VMS

I just checked this to be sure - it is 750. Be careful with this in an exam - the notation can use +, - and =. They probably put this in to catch you out. Besides all that it wouldn't make sense to give other more access than group anyway.

nobodythere

Nice one, thanks.

I do need two ways though.

For (a) I'd be chancing my hole to change the "u=" to "u+" yes?
For (b) there's cd ~ OR cd /home/username
For (c) I have: sed -n "/unix/p" < readme.txt | wc -l
For (d) I haven't a clue.

a) chmod u=rwx,g=rx,o-rwx <filename>
b) cd $HOME
c) cat readme.txt | grep unix | wc -l
d) mkdir "A directory name with spaces!"

Orion

I gave you others for c & d:

c) grep -o <string> <filename> | wc -l
and ethernet's "grep unix < readme.txt | wc -l" will do it too.
d) mkdir a\ directory\ name\ with\ spaces/

Can't think of a second one for d though.
In a I don't think you'd get away with + instead of =. If, for example, group already had 'w' you'd be adding rx to give rwx not rx as requested.

Orion

Bit messy but here's a valid alternative for a)

chmod ug=rx,u+w,o-rwx filename

so along with:
chmod 750 <filename>

there's your two options.

nobodythere

Macros42 wrote: »

Bit messy but here's a valid alternative for a)

chmod ug=rx,u+w,o-rwx filename

so along with:
chmod 750 <filename>

there's your two options.

Thanks, I didn't put the full list in that last post, only the second alternatives I had.

I was thinking about (d):
MYDIR="blah blah"; mkdir $MYDIR

I might get away with that. however it doesn't work (I tried escaping the quotes)...

ethernet

Forgot to mention a plain old 'cd' without any params will always bring you to your home directory.

Stumped to come up with something noticeably different for d.

Best of luck

djmarkus

Keep it nice and simple

b) cd $(getent passwd $(id -un) | cut -d: -f6)

d) mkdir 'A directory name with spaces!' or

Infact mkdir "A directory name with spaces!" doesnt actually work in bash.

Orion

djmarkus wrote: »

Infact mkdir "A directory name with spaces!" doesnt actually work in bash.

Yes it does. Just tested it. At least it does in Ubuntu.

djmarkus

dmarkey@dmarkey-XPS:~> mkdir "A directory name with spaces!"
bash: !": event not found

Dunno what kind of shell ubuntu is using these days.

Orion

steve@Sethanon:~$ bash
steve@Sethanon:~$ mkdir "test dir"
steve@Sethanon:~$ cd test\ dir/
steve@Sethanon:~/test dir$ 

Just a thought - Unix tests don't rely on bash anyway. They are based on sh usually. That's installed on every flavour of *nix whereas bash isn't. And just tested mkdir "test dir" in sh too - it works.

steve@Sethanon:~$ sh
$ mkdir "test dir"
$ cd test\ dir
$ pwd
/home/steve/test dir

djmarkus

try the command that was quoted at the start, namely

mkdir "A directory name with spaces!"

This however.

mkdir "A directory name with spaces\!"

will work

Orion

steve@Sethanon:~$ mkdir "A directory name with spaces!"
mkdir "A directory name with spaces"
steve@Sethanon:~$ cd A\ directory\ name\ with\ spaces/
steve@Sethanon:~/A directory name with spaces$ 

What distro are you using?

[edit]Ah - the ! is throwing it - it's echoing the result. Try mkdir "A directory name with spaces" in your distro (no !)

djmarkus

OpenSuSE

Tested on Solaris also. Ubuntu must have done something strange with bash.

Edit:

I see whats going on, you're using dash on ubuntu these days.

Orion

Just tested it on my digiweb shell account too - not Ubuntu.

$ cat /etc/issue
CentOS release 4.4 (Final)

[username@web2 account.net]$ mkdir "test dir"
[username@web2 account.net]$ cd test\ dir/
[username@web2 test dir]$

Orion

djmarkus wrote: »

I see whats going on, you're using dash on ubuntu these days.

Look at my post - I specifically entered bash to test.

steve@Sethanon:~$ bash
steve@Sethanon:~$ mkdir "test dir"
steve@Sethanon:~$ cd test\ dir/
steve@Sethanon:~/test dir$

[edit]and bash is my default shell on Ubuntu:
steve@Sethanon:~$ echo $SHELL
/bin/bash


[edit2]Bit puzzling why it won't work for you - if it's accepted in sh then it should be accepted in all shells. Maybe Suse is doing something odd not Ubuntu or CentOS. Too late for me to think tho - off to bed. Google time tomorrow methinks

Skrynesaver

grasshopa wrote: »

I was thinking about (d):
MYDIR="blah blah"; mkdir $MYDIR

I might get away with that. however it doesn't work (I tried escaping the quotes)...

The reason this won't work is that when $MYDIR is evaluated it contains individual words separated by spaces, each of which is seen as a separate parameter.

In fact, as has been pointed out by others, the presence of a bang in the interpolated(double) quotes means that the command won't run in bash as written.

The following would have the same effect as the provided command

echo 'bash: !": event not found' && false

Khannie

single quotes for the mkdir remove interpolation.

e.g.

mkdir 'my dir!' will work fine

edit: I'm not being a smart arse. It's an important difference...

i=test
mkdir '$i'

actually makes a directory called $i (i.e. not test).

PhantomBeaker

Seeing as all require two different implemenations, here's a smartass one for c):

awk ' BEGIN { count=0 } /unix/ { count++ } END { print count }' filename

However, I realise this is a bit late, and hope you did well in your exam.

Aoife