GNU/Linux

bash: Simple way to get n-th column

 in Bash / GNU/Linux  tagged column / cut / delimiter by

Using cut you can select any column and define a custom delimiter to support multiple input formats you can select a column (or more) with barely minimum code.

cut -d',' -f2 myFile.csv

The above command will read the file myFile.csv (which is a CSV file) break it down to columns using the ‘,‘ character and then get the second column.

The option -f specifies which field (column) you want to extract, and the option -d specifies what is the field delimiter (column) that is used in the input file.

The -f parameter allows you to select multiple columns at the same time. You can achieve that by defining multiple columns separated using the ‘,‘ and by defining ranges using the - character.

Examples

  • -f1 selects the first column
  • -f1,3,4 selects columns 1, 3 and 4
  • -f1-4 selects all columns in the range 1-4
  • -f1,3,5-7,9 selects columns 1,3,8 and all the columns in the range 5-7

Fedora 23: Support exfat

 in GNU/Linux  tagged exfat / fedora / fuse-exfat / rpmfusion by

The Background:

Recently we got our hands on a GoPro Hero4 Black camera and we used a 64GB memory card as storage. The file system on the card is exFAT (Extended File Allocation Table), which is a Microsoft file system designed for flash drives. It is proprietary and Microsoft owns patents on several elements of its design. exFAT has been adopted by the SD Card Association as the default file system for SDXC cards larger than 32GiB.

The issue:

Fedora does not support exFat due to the licensing issues that Microsoft applied to the product and thus we could not mount the card on our machine.

The solution:

We installed the fuse-exfat driver from rpmfusion.org using the following commands.

#Enable access to both the free and the nonfree repository
#free repository: for Open Source Software (as defined by the Fedora Licensing Guidelines) which the Fedora project cannot ship due to other reasons
#nonfree repository: for redistributable software that is not Open Source Software (as defined by the Fedora Licensing Guidelines); this includes software with publicly available source-code that has "no commercial use"-like restrictions 
su -c 'dnf install http://download1.rpmfusion.org/free/fedora/rpmfusion-free-release-$(rpm -E %fedora).noarch.rpm http://download1.rpmfusion.org/nonfree/fedora/rpmfusion-nonfree-release-$(rpm -E %fedora).noarch.rpm';

#Perform the installation
sudo dnf install fuse-exfat;



More background:


RPM Fusion provides software that the Fedora Project or Red Hat doesn’t want to ship. That software is provided as precompiled RPMs for all current Fedora versions and Red Hat Enterprise Linux 5 and 6.

ffmpeg: Extract audio from .MKV to .MP3 13

 in Bash / GNU/Linux  tagged audio / extract / ffmpeg / mkv / mp3 / video by

The following command will find all mkv files that are in the current directory and in all sub-folders and extract the audio to mp3 format.

find . -type f -name "*.mkv" -exec bash -c 'FILE="$1"; ffmpeg -i "${FILE}" -vn -c:a libmp3lame -y "${FILE%.mkv}.mp3";' _ '{}' \;

The filename of the audio file will be the same as the mkv video with the correct extension. The mkv extension will be removed and replaced by the mp3 extension e.g hi.mkv will create a new file named hi.mp3

Git: Delete all local branches

 in Bash  tagged delete / fetch / git / grep / local branch / merged / prune / xargs by

The following command will:

  • print all branches that were merged to master
  • then filter out the branch named master and the branch you are currently switched to
  • and finally, it will delete the rest (one branch at a time).
git branch --merged master | grep -v -e "\*" -e "master" | xargs git branch -D

Tip:

To cleanup any remote-tracking references that no longer exist on the remote use the following:

git fetch --prune