Command-Line-Fu

Last modified: Mar, 2016

A collection of random but useful command lines. The OS is assumed to be Ubuntu.

Batch process images

To resize all images in one folder, first install imagemagick.

sudo apt-get install imagemagick

Then in the folder, run bash script:

for img in `ls *.JPG`
  do 
  mogrify -resize 50% $img
done

Networking

About IPv6 related commands: at the time of writing (Mar, 2016) IPv6 is still in the adopting stage and not every server can talk in IPv6.

• To ssh into a IPv6 only Linux box:

ssh -6 user@3509:5600:02e4:0000:0000:0000:098e:2abf

which is very similar to the traditional way.

• To ping IPv6 addresses/host names, do

ping6 ipv6.google.com

Directory and File Operations

• Show meta information of hidden files with “du” (reference here):

du -sch .[!.]* * |sort -h

• Change text pattern in files recursively:

find path_to_folder -type f -print0 | xargs -0 sed -i 's/patternA/patternB/g'

See this post for explanation.

• Compare the content of files in two directories recursively:

diff -qr -x "*.o" -x "*.html" -x "*.bin" dir1 dir2

Here the “-x” flag excludes the files to be compared.

• A “live” view of a log file using tail

cat log.txt | tail -f