Change Directory and list contents in single command.

I find myself often changing to a directory and immediately performing an `ls`. This is partly habit and partly the fluid nature nature of the files I work on.  Anyway, you don't care about that...

Using an editor of your choosing open your .bashrc or .bash_profile and add the following lines:

# User defined functions
function cdl { cd $1 && echo $PWD && ll; }

Note: In the above I have aliased `ll` as ->  alias ll='ls -ASlh'
Note: You can name this whatever you choose, I just think `cdl` made sense.
Note: You can omit the echo $PWD if you don't care to see the directory path in the output. So you could do something as simple as:

# User defined functions
function cdl { cd $1 && ls; }

Save and close and then

bkarels@rev0:~$ source ~/.bashrc

Now you can use cdl (or whatever you've named it to change directory and immediately ls the contents.

Example:

bkarels@rev0:~$ cdl foo/

/home/bkarels/foo
total 328K
-rw-------   1 bkarels bkarels 156K Aug  8 09:39 sample0
-rw-------   1 bkarels bkarels 6.9K Aug  8 08:47 someFile27
-rw-r--r--   1 bkarels bkarels 4.1K Aug  7 12:07 sayWhat
drwx------   6 bkarels bkarels 4.0K Aug  8 07:37 killWindows.exe

The above example was done on Debian 7 (Wheezy) but should work on all flavors of *nix and OSX.

FIN

Generate SHA hash - OSX

I'll have to clean this post up later, but just to get this down.  Pulled the new Fedora 18 XFCE spin from the torrent and needed to verify it with the provided SHA256 hash.

At it's most basic:

computer:directory user$ shasum <filename>
<some_hash> <filename>

In the case below I needed a SHA256 hash so the -a arg was necessary:

computer:directory user$ shasum -a256 <filename>

<some_256_hash> <filename>

So, here is what I did - some content removed for brevity(...):

berlin:tmp bkarels$ cat Fedora-18-x86_64-Spins-CHECKSUM
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256
...
95a75c...29dd6e *Fedora-18-x86_64-Live-XFCE.iso
berlin:tmp bkarels$ shasum -a256 Fedora-18-x86_64-Live-XFCE.iso
95a75c...29dd6e  Fedora-18-x86_64-Live-XFCE.iso

Checking the hash against a provided list was not as clear from the man pages.  In brief you need to use the output of a shasum as input to shasum -c.  Here you need only find 'OK' vs. relying on your human ability to visually compare hashes on a terminal.

Basic:

computer:directory user$ shasum -a 256 <filename> | shasum -c <CHECKSUM_FILE>
blah blah blah output: OK

Example:

berlin:tmp bkarels$ shasum -a 256 Fedora-18-x86_64-Live-XFCE.iso | shasum -c Fedora-18-x86_64-Spins-CHECKSUM
...
shasum: Fedora-18-x86_64-Live-Scientific-KDE.iso: No such file or directory
Fedora-18-x86_64-Live-Scientific-KDE.iso: FAILED open or read
shasum: Fedora-18-x86_64-Live-Security.iso: No such file or directory
Fedora-18-x86_64-Live-Security.iso: FAILED open or read
shasum: Fedora-18-x86_64-Live-SoaS.iso: No such file or directory
Fedora-18-x86_64-Live-SoaS.iso: FAILED open or read
Fedora-18-x86_64-Live-XFCE.iso: OKshasum: WARNING: 7 of 8 listed files could not be read

Fin.

NOTE: For clarity, here is the entire contents of the example file Fedora-18-x86_64-Spins-CHECKSUM:

berlin:tmp bkarels$ cat Fedora-18-x86_64-Spins-CHECKSUM
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256
3684ae2814c7e54b4f66f0411a385846533e40f107d7fff4e331c2f547951ec2 *Fedora-18-x86_64-Live-Design-suite.iso
b11da64d527e333e2160cbf5fde49f89205f932d48fa7c01690232fc1b0cacfa *Fedora-18-x86_64-Live-Electronic-Lab.iso
ea34f626488623a1f84b2041df9c65468357bfdb878f034392da16f6c9d05264 *Fedora-18-x86_64-Live-LXDE.iso
8700aa64a6485e338b3d9aa419ecadc0c87884c77203a35c6e1847147a4dca06 *Fedora-18-x86_64-Live-Robotics.iso
3bb90d115daf6f0d2279cd5a669fb265c090cb6e88125424ae960a980f9ba50d *Fedora-18-x86_64-Live-Scientific-KDE.iso
7802a1c024f9471fba90724f53c0d95045acd76c3c4346b467cb53f5608248a9 *Fedora-18-x86_64-Live-Security.iso
736e8dd36de4207fe899648299abb6b3220fd1d1bcb48b8bf712d01d2ec02bf5 *Fedora-18-x86_64-Live-SoaS.iso
95a75c334ce82b33f1a5d81eab196600e40c7933fd5f7bfa8e6ed9534529dd6e *Fedora-18-x86_64-Live-XFCE.iso
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.11 (GNU/Linux)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=/hTc
-----END PGP SIGNATURE-----

Set tabstop in VI - Mac OSX

From within VI

(Assuming you would like to use four spaces for your tabs)
:set tabstop=4

To make this behaviour the default:

user@machine:~$ cd ~
(if ~/.exrc does not exist, create it.  Otherwise skip to next cmd.)
user@machine:~$ touch .exrc
user@machiner:~$ vi .exrc

Add the following line to the file:
set tabstop=4


Save and close .exrc

user@machine:~$ . .exrc
user@machine:~$ vi someTextFile.txt

Basically, if the file .exrc does not exist in your home directory create it.
Open .exrc for editing.
Add the line (w/o quotes) "set tabstop=4"
Save .exrc
Source .exrc
Test to verify function.

This should also work in most flavors of *nix.

~Fin

OS X::10.6 - configure: error: C compiler cannot create executables

Ran into this trying to compile Apache Httpd:

Configuring Apache Portable Runtime Utility library...

checking for APR-util... yes
checking for gcc... gcc
checking for C compiler default output file name...
configure: error: in `/Users/bkarels/devtools/httpd-2.2.17':
configure: error: C compiler cannot create executables
See `config.log' for more details.

Mac OS X solution:

Go back to: Snow Leopard DVD > Optional Installs > Xcode.mpkg:

Option: System Tools > Checked
Option: UNIX Dev Support > Checked <-- Important

Run installer. No reboot necessary. Compiler commands execute as expected.

Credit to solution author kevinx.
Original thread from discussions.apple.com: can be found here.

"Remote" administration of Linux VirtualBox® Guest Virtual Machines

Sometimes you just need a sandbox of your very own. Oracle's VirtualBox has long offered a way to let you play with a guest OS on your host system - but what if you need to interact with the guest from your host? In my case I wanted to simulate a sharded MongoDB cluster that, to be a true simulation, required a minimum of three servers.

Here we will go over the process of setting up your virtual machine in such a way that you can "remote" administer it and connect to it like any server on your network. For this example I will be running and OS X host with a Ubuntu Server 10.10 guest.

1. Download and install Oracle VirtualBox® here.

2. With VirtualBox® installed, let's take a look at our network settings on the host machine with `ifconfig`. Here you will want to take note of the vboxnet0 address:



3. Add a new virtual machine using the Oracle VM VirtualBox Manager. Once the initial setup is complete select the new virtual machine can click on the network adapter to add a second:



4. Adapter #1 will be configured by default and does not need to be altered. Click on the tab for `Adapter 2`, enable, and configure as follows:



5. Click the green arrow in the VM Manger to start the new virtual machine and install the new guest. (the rest of this example assumes a guest of type Ubuntu Server 10.10 but should be very similar for all flavors of *nix.)

6. During the guest install be sure to select eth0 as the primary network adapter.



7. Also, to save the need to set up the OpenSSH Server later, you can elect to do so as part of the OS install.



8. Start up the new guest and login.

9. Configure eth1 by modifying /etc/network/interfaces Add the following lines:
(NOTE: The address below is made up from the VBoxnet0 address noted in Step 2 above. Since mine defaulted to 192.168.56.1 I was free to use any value beyond that as below.)

# Secondary network interface for VBox0
auto eth1
iface eth1 inet static
address 192.168.56.102
netmask 255.255.255.0

10. Save and close /etc/network/interfaces and bring up eth1 using:

sudo ifup eth1

Your terminal might look like this when done:



11. Open a terminal on your host machine and connect to your guest using SSH:



If all went well you should be connected via SSH to your guest system and be able to interact with it as you would any server on your network. So, let's fire up a remote MongoDB server on our guest and verify that we can reach the Http Interface for the instance.

Starting up mongod on port 27000 on mongo2 (Http Interface defaults to [port] + 1000 or 28000 in this case):



...and voilà! We are connected to our "remote" instance.



Fin

Using custom shell scripts on Linux & OSX

You need to create a custom shell script and would like to run it from anywhere on your system.

1. Create a `bin` directory to store your script.

machine:~ user$ mkdir ~/bin

For Linux users this will create /home/[user]/bin, for OSX you'll have /Users/[user]/bin. You could name this directory whatever you'd like, but bin seems fitting.

2. Modify .bashrc or .bash_profile to put `bin` on your path.

If you're comfortable with vi you can: (Alternatively use any text editor you are comfortable with)

machine:~ user$ vi ~/.bash_profile [OSX]
user@machine:~$ vi ~/.bashrc [Linux]

Either way, add the following line:

PATH=$PATH:$HOME/bin

3. Save and exit.

4. Source your file for it to take effect:

machine:~ user$ . ~/.bash_profile [OSX]
user@machine:~$ . ~/.bashrc [Linux]

5. Now you can drop a shell script into your bin directory and have executable from anywhere on your filesystem (don't forget to make it executable!)

Example:

Last login: Thu Mar 31 11:07:30 on ttys004
machine:~ user$ pwd
/Users/user
machine:~ user$ touch example
machine:~ user$ vi example
...

#!/bin/sh
echo "Somewhere in Russia a little girl is warming up with your max."

...
machine:~ user$ mv example ~/bin/
machine:~ user$ chmod +x ~/bin/example
machine:~ user$ ls -l ~/bin | grep example
-rwxr-xr-x 1 user staff 80 Mar 31 14:25 example
machine:~ user$ cd /tmp/
machine:tmp user$ example
Somewhere in Russia a little girl is warming up with your max.
machine:tmp user$

Fin

Lift weights - Lift spirits

Simple command line encryption

Works on OS X, Linux, anywhere with OpenSSL installed:
(NOTE: With OS X Lion breaking TrueCrypt - this is simple replacement that, in a way, simplifies things.)

To encrypt the file:

openssl des3 -salt -in infile.txt -out encryptedfile.txt

To decrypt the file:

openssl des3 -d -salt -in encryptedfile.txt -out normalfile.txt

The -a option, stores the encrypted file in base64 instead of binary.

To encrypt the file stored in base64:

openssl des3 -a -salt -in infile.txt -out encryptedfile.txt

To decrypt the file stored in base64:

openssl des3 -d -a -salt -in encryptedfile.txt -out normalfile.txt

To see a list of all available ciphers and other command information:

openssl -h

Other examples(notes to self...):
openssl des3 -salt -in rev27_*****_2010.zip -out rev27_*****_2010.zip.des3
openssl des3 -salt -in pf_*****_2010.zip -out pf_*****_2010.zip.des3

View output in console and write to file using tee - Mac OS X 10.6.4

Use tee to send output to the console and to a file:

machine:dir user$ ./some_program | tee output_file.txt

Executing the above command will display the output of some_program immediately in the console and write the same contents to output_file.txt.

I use this command mostly for diffs against svn, saves a step. Also, though I'm posting this as a Mac OS X terminal option, I first discovered this on Ubuntu 8.04 though I sure the history or this command is much older. I recall from the documentation to think of this in plumbing terms: Send your output down a pipe to a "T" essentially sending the same stream/flow to two different places.

~Fin

Show line numbers in VI - Ubuntu Linux 9.04 Jaunty/Mac OS X

Update - verified to work also with Mac OS X

From within VI
:set number

To make this behaviour the default:
user@machine:~$ cd ~
user@machine:~$ touch .exrc
user@machiner:~$ vi .exrc

Add the following line to the file:
set number
user@machine:~$ . .exrc
user@machine:~$ vi someTextFile.txt

Basically, if the file .exrc does not exist in your home directory create it.
Open .exrc for editing.
Add the line (w/o quotes) "set number"
Save .exrc
Source .exrc
Test to verify function.

Update (as I've had to look this up twice now...)
To turn off line numbers from withing VI
:set nonumber

~Fin