Ubuntu – What does su > echo “” mean

bashcommand linesudo

When I was entering the command

su > echo  "sachin"

it was asking for a password. When I gave my password, some strange things happened as you can see:

Enter image description here

One more thing: there is another user, Hadoop, on my laptop, but when I do

su > echo "Hadoop"

it says

no passwd entry for Hadoop

What does this mean?

Best Answer

Ah! Nice puzzle!

Just say "exit", and all your files will be there (and the output you miss in a file called echo).

Explication:

 su > echo user

is the same as

 su user > echo

So you are starting a (sub)shell with su (switch user) to your user, with all output redirected to a file called echo!

Look:

[romano:~] % cd tmp/dvd-usa-hd 
[romano:~/tmp/dvd-usa-hd] % ls
dvd-usa-hd_01_01.avi
[romano:~/tmp/dvd-usa-hd] % su > echo romano
Password: 
[romano:~/tmp/dvd-usa-hd] % ls
[romano:~/tmp/dvd-usa-hd] % exit
[romano:~/tmp/dvd-usa-hd] % ls
dvd-usa-hd_01_01.avi  echo
[romano:~/tmp/dvd-usa-hd] % cat echo
dvd-usa-hd_01_01.avi
echo
[romano:~/tmp/dvd-usa-hd] %

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Ubuntu – What does the “apt-get dselect-upgrade” command do

As others have pointed out, it "follows dselect choices". One nice thing about this, is one can feed a list of packages selections to dpkg:

dpkg --clear-selections
dpkg --set-selections < package_choice_list

then do "apt-get dselect-upgrade" and it will remove anything not in the list, and install everything in the list. I don't think any other package tool can do that. It gives one a way to ensure "these and only these" packages are installed, which is very convenient.

Ubuntu – Can’t pass the variable into other command

You should use command substitution and for doing that you are missing a $.

You should also pipe the content of your variable to cut or read it from stdin.

So use this instead:

$ exampleVariable="[$(cut -d: -f1 <<<$passwdContent )]"

Now:

$ echo "$exampleVariable"
[ravexina]

Best Answer

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