Shell Programming and Scripting

Hi I have a requirment here. I have to out the string after the particular word. for example i have the to extract the first word after the word disk. help me out. i have tried the folloing code but it is not giving the output which i need.
awk -F"*disk " '{print $1}'
grep -n -o '[Disk]' file

Input :

I have the disk A which stores Songs.
ram has huge disk B which stores movies and games.
sethu have small capcity disk c which holds program documents and other apps.

output:
A
B
C

Code:

awk '{for(i=1; i<=NF; i++){if($i == "disk"){print $(i+1); next}}}' file

Code:

grep -o 'disk [^ ]*' file | cut -d' ' -f2

Code:

sed 's/.*disk \([^ ]*\).*/\1/' file

With GNU grep:

Code:

grep -oP '(?<=disk\s)\S' file

Try:

Code:

$ awk -F'disk ' '{split($2,a," "); print a[1]}' input.txt
A
B
C