user10726006's questions

I have two ubuntu computer shared the same wifi and desire to reach another from one's terminal.

First create an user on the second computer named "Second" and hostname "Algorithms"

Then tried to reach it from the other with SSH, but get error report as

$ ssh second@Algorithms  
ssh: Could not resolve hostname algorithms: nodename nor servname provided, or not known

The solution I tried is based on networking - Reach other computer from the local - Ask Ubuntu

What's the problem with my experiment?

I learned from the book "Harley Hhan's Guide to Unix and Linux".
In chapter 3 of "The Unix Connection", it instruct to establish a local area network.

You can see this illustrated in Figure 3-6. In Figure 3-6, the network connections between the PC and the three Unix hosts are via cables, as in a traditional network. However, any type of network connection will do. In particular, you can use a wireless connection.

Here is an example. Let’s say you have three geeky friends, Manny, Moe and Jack. Each of you has a laptop computer that runs Unix. You use Debian Linux; Manny uses Fedora Core Linux; Moe uses Gentoo Linux; and Jack uses FreeBSD. (Jack always was a bit odd.)

You get together for a Unix party (that is, computers, caffeinated drinks, and junk food), and you decide that each person should have access to the other three computers. First, each of you creates user accounts on your own computer for the other three people. (I won’t go into the details here, but it’s not hard.)

I created user account on two computer but have no idea how to reach another from one.

Do I miss any points? Could you offer any hints?

I am learning file mode permissions

666: for non-executable ordinary files 
777: for executable ordinary files 
777: for directories

Reference to the executable mode,
I could understand that a program file has executable mode, but have
no ideas about why a directory also has a 'executable mode`.

I found it make no sense. a directory entry cannot be executed and cannot set all the files within a directory 'executable` by just set their directory.

How to understand a executable directory entry?

I'd like to count all the ordinary file on home directory with commands:

$ find ~ -type f | xargs echo | wc -w
xargs: unmatched single quote; by default quotes are special to xargs unless you use the -0 option

It prompts

xargs: unmatched single quote; by default quotes are special to xargs unless you use the -0 option

What's the problem with usage?

I use the command whereis rm

$ whereis rm
/bin/rm

Then I try which rm

$ which rm
/usr/local/opt/coreutils/libexec/gnubin/rm

The results are different... so which rm will be called when I run a command like rm readme?

I have the following files

$ ls *.md | sort -n
1.pythonPrimer.md
10.mapsHashTablesAndSkipLists.md
11.searchTree.md
12.sortAndSelection.md
13.textProcessing.md
14.graphAlgorithms.md
15.memoryManagementAndBTrees.md
16.Appendix.md
2.Object Oriented Programming.md
3.algorithmsAnalysis.md
4.recursion.md
5.arrayBasedSequence.md
6.stack.md
7.linkedList.md
8.tree.md
9.priorityQueues.md

I want to sort them by the leading numbers in the order 1, 2, 3, 4....,

How could I get it done?

I have the following files:

$ ls *.png | egrep -i "am|pm"
output-0 11.42.30 AM.png
output-0 5.10.12 PM.png
....

I want to remove them but get this error:

$ ls *.png | egrep -i "am|pm" | while read line; do rm "$line"; done
rm: cannot remove ''$'\033''[0m'$'\033''[01;35moutput-0 11.42.30 AM.png'$'\033''[0m': No such file or directory
rm: cannot remove ''$'\033''[01;35moutput-0 5.10.12 PM.png'$'\033''[0m': No such file or directory
rm: cannot remove ''$'\033''[01;35moutput-1 11.42.30 AM.png'$'\033''[0m': No such file or directory

What's the problem with my codes?

I tried to convert an pdf to multiple pngs

 $ convert -density 150  1.primer.pdf  -quality 100 output.png

it work well but the output starts with 0

$ ls | grep png | sort -n
output-0.png
output-1.png
output-10.png
output-11.png
output-12.png

How could I modify it to start with 1?