xyz's questions

In a Unix shell, how can I pick a single line from a text file by its line number?

Say I want whatever is at line 3 in animals.txt to be written to stdout (bat bat bat).

monkey monkey monkey
cat cat cat
bat bat bat
horse horse horse

Is there a standard program or simple way to do this?

(There's also the case where the text file does not contain enough lines to contain the line number you ask for)

On Mac OS X, .DS_Store files seem to contain custom view settings for the directory when it is viewed in Finder (file manager GUI). I want every directory to use my default view settings.

Is this shell command safe to delete all of them (that I have permission to) from the drive? i.e. no chance or false positives or other mishaps.

cd /
find . -name .DS_Store -print0 2>/dev/null | xargs -0 -p rm

netcat [...] -e program
nc [...] -e program

Is supposed to run program as a server (as far as its stdin and stdout are concerned). netcat on Mac OS X does not seem to have this -e option.

Why is that and is there a way to enable it?

Could you help me with the Bash syntax to achieve the following?

1. Run a blocking process without blocking execution of the rest of the script.
2. Run a standard "non-blocking" process (e.g. lsof).
3. "Rejoin" the blocking process so that ^C will stop that process, then end execution of the script.

Say you own a abcd.com and you only want to use it to send and receive email via [email protected]. You don't want to provide any kind of website.

Can you set up the DNS records to include an "MX" record and no "A" record?

• Is this enough for sending and receiving email to work?

• Is this valid in terms of whatever standard defines these things?

Edit: To clarify, the mail server (terminology?) would not be hosted on abcd.com or *.abcd.com

I'm using Mac OS X and I manually compiled llvm and clang because they were not available from MacPorts (a package manager).

I presume clang has some kind of man page. How do I install and/or activate it so that I can access it with man clang?

To use SSL, the web server that I am using requires the location of a single .pem file (-ssl_cert xyz.pem)

I have a certificate issued by GoDaddy. They gave me the file:

banana.crt

The preceding certificate request was created using a private key I generated

banana.key

Googling seems to suggest that creating a .pem file is as simple as concatenating them.

cat banana.key banana.crt > banana.pem

Unfortunately, starting the server with banana.pem, and visiting it with Safari tells me:

Issued by: Go Daddy Secure Certificate Authority

This certificate was signed by an unknown authority

What's going wrong? Have I or GoDaddy screwed something up in the creation of the certificate, or do I somehow have to mix something from here in to my .pem file?

I'm visiting with a fully up to date OS X Leopard + Safari installation.

I'd like to run a web server to experiment with. I'm going to to use Mongoose because it looks lightweight and simple enough to understand everything that it is doing.

I have a Debian box to run it on.

My questions are

• Is it advisable to run a web server as root? If not, why not? (How can a non-privileged accounts listen on ports 80,443?)

• Is there a standard directory to put the "site root" to be served? Does it matter where this is as far as security considerations go?

What software is out there that allows a mouse and keyboard to be shared between 2+ networked computers?

I know about Synergy, but what are the alternatives? Which do you like the best?

I'm personally most interested in something compatible with both Mac OS X and Windows, but software that is limited to certain platforms is still of interest, so please mention it.