Reloading .bashrc within a BASH terminal session

BASH is a command-line interpretor that is commonly used by Linux and UNIX operating systems. Chances are that you will find find yourself in a BASH session if you start up a terminal emulator in many of these though there are others like KSH and SSH too.

BASH comes with its own configuration files and one of these is located in your own home directory, .bashrc. Among other things, it can become a place to store command shortcuts or aliases. Here is an example:

alias us=’sudo apt-get update && sudo apt-get upgrade’

Such a definition needs there to be no spaces around the equals sign and the actual command to be declared in single quotes. Doing anything other than this will not work as I have found. Also, there are times when you want to update or add one of these and use it without shutting down a terminal emulator and restarting it.

To reload the .bashrc file to use the updates contained in there, one of the following commands can be issued:

source ~/.bashrc

. ~/.bashrc

Both will read the file and execute its contents so you get those updates made available so you can continue what you are doing. There appears to be a tendency for this kind of thing in the world of Linux and UNIX because it also applies to remounting drives after a change to /etc/fstab and restarting system services like Apache, MySQL or Nginx. The command for the former is below:

sudo mount -a

Often, the means for applying the sorts of in-situ changes that you make are simple ones too and anything that avoids system reboots has to be good since you have less work interruptions.

Batch conversion of DNG files to other file types with the Linux command line

At the time of writing, Google Drive is unable to accept DNG files, the Adobe file type for RAW images from digital cameras. The uploads themselves work fine but the additional processing at the end that I believe is needed for Google Photos appears to be failing. Because of this, I thought of other possibilities like uploading them to Dropbox or enclosing them in ZIP archives instead; of these, it is the first that I have been doing and with nothing but success so far. Another idea is to convert the files into an image format that Google Drive can handle and TIFF came to mind because it keeps all the detail from the original image. In contrast, JPEG files lose some information because of the nature of the compression.

Handily, a one line command does the conversion for all files in a directory once you have all the required software installed:

find -type f | grep -i “DNG” | parallel mogrify -format tiff {}

The find and grep commands are standard with the first getting you a list of all the files in the current directory and sending (piping) these to the grep command so the list only retains the names of all DNG files. The last part uses two commands for which I found installation was needed on my Linux Mint machine. The parallel package is the first of these and distributes the heavy workload across all the cores in your processor and this command will add it to your system:

sudo apt-get install parallel

The mogrify command is part of the ImageMagick suite along with others like convert and this is how you add that to your system:

sudo apt-get install imagemagick

In the command at the top, the parallel command works through all the files in the list provided to it and feeds them to mogrify for conversion. Without the use of parallel, the basic command is like this:

mogrify -format tiff *.DNG

In both cases, the -format switch specifies the output file type with tiff triggering the creation of TIFF files. The *.DNG portion itself captures all DNG files in a directory but {} does this in the main command at the top of this post. If you wanted JPEG ones, you would replace tiff with jpg. Shoudl you ever need them, a full list of what file types are supported is produced using the identify command (also part of ImageMagick) as follows:

identify -list format

Resolving Windows Update Error 0x80244019 on Windows 10

In Windows 10, the preferred place to look if you fancy prompting an update of the system is in the Update & Security section of the Settings application. At the top is the Windows Update and the process usually is as simple as pressing the Check for updates button. For most the time, that has been my experience but it stopped working on my main Windows 10 virtual machine so I needed to resolve the problem.

Initially, going into the Advanced Options section and deselecting the tick box for Give me updates for other Microsoft products when I update Windows helped but it seemed a non-ideal solution so I looked further. It was then that I found that manually resetting a system’s Windows Updates components helped others so I tried that and restarted the system.

The first part of the process was to right click on the Start Menu button and select the Windows Powershell (Admin) entry from the menu that appeared. This may be replaced by Command Prompt (Admin) on your system on your machine but the next steps in the process are the same. In fact, you could include any commands you see below in a script file and execute that if you prefer. Here, I will run through each group in succession.

From either Powershell or the Command Prompt, you need to stop the Windows Update, Cryptographic, BITS (or Background Intelligent Transfer Service) and MSI Installer services. To do this, execute the following commands at a command prompt:

net stop wuauserv
net stop cryptSvc
net stop bits
net stop msiserver

With the services stopped, it is then possible to rename the SoftwareDistribution and Catroot2 folders so you can refresh everything to remove the .To do this, execute the following pair of commands using either Powershell or the Command Prompt:

ren C:\Windows\SoftwareDistribution SoftwareDistribution.old
ren C:\Windows\System32\catroot2 Catroot2.old

Once you have the folders renamed, then you can start the Windows Update, Cryptographic, BITS and MSI Installer services by executing the following commands in either Powershell or the Command Prompt:

net start wuauserv
net start cryptSvc
net start bits
net start msiserver

Once these have completed, you may close the Powershell or Command Prompt window that you were using and restart the machine. Going in to the Update & Security section of the Settings tool afterwards and pressing the Check for updates button now builds new versions of the folders that you renamed and this takes a little while longer than the usual update process. Otherwise, you could let your system rebuild things in its own time. As it happens, I opted for manual intervention and all has worked well since then.

Windows commands for setting default applications for opening certain file types

On Friday, I was working on a system where a session is instantiated from a stored virtual machine that produces a fresh session every time so all previous changes get lost. What I have is a batch script that I run to reinstate what I need and I encountered another task that I wanted it to do.

Part of my work involves the creation of plain text files with the extension lst and this is getting associated with SAS instead of Notepad. While you can reassign such associations using the GUI, it would be nice to do it via the command line too so the assoc and ftype commands caught my interest. The first of these associates a file with a given extension with a desired file type while the second shows the available file types together with the associated applications that open them. The assoc command also show all the associations that are in place when it is executed with no parameters and the ftype command does the same for file types.

Once you have picked out a file type with the ftype command, then the assoc can be used like the following:

assoc .lst=txtfile

The above associates an extension with a file type. In the this, .lst files are going to get opened by Notepad because of the txtfile association. Though it did not do what I wanted on Friday due to system lockdown, it is good to know that this is possible and that even the Windows command line supports goodies like these.

A few more shell commands

Here are some Linux commands that I encountered in a feature article in the current issue of Linux User & Developer that I had not met before:

cd --

This returns you to the previous directory where you were before with having to go back through the folder hierarchy to get there and is handy if you are jumping around a file system and any other means is far from speedy.

lsb_release -a

It can be useful to uncover what version of a distro you have from the command line and the above works for distros as diverse as Linux Mint, Debian, Fedora (it automatically installs in Fedora 22 if it is not installed already, a more advanced approach than showing you the command like in Linux Mint or Ubuntu), openSUSE and Manjaro. These days, the version may not change too often but it still is good to uncover what you have.

yum install fedora-upgrade

This one can be run either with sudo or in a root session started with su and it is specific to Fedora. The command performs an upgrade of the Fedora distro itself and I wonder if the functionality has been ported to the dnf command that has taken over from yum. My experiences with that in Fedora 22 so far suggest that it should be the case though I need to check that further with the VirtualBox VM that I have created.