One command to create a directory and file inside it linux command

mkdir B && touch B/myfile.txt

Alternatively, create a function:

mkfile() { mkdir -p -- "$1" && touch -- "$1"/"$2" }

Execute it with 2 arguments: path to create and filename. Saying:

mkfile B/C/D myfile.txt

would create the file myfile.txt in the directory B/C/D.

For this purpose, you can create your own function. For example:

$ echo 'mkfile() { mkdir -p "$(dirname "$1")" && touch "$1" ;  }' >> ~/.bashrc
$ source ~/.bashrc
$ mkfile ./fldr1/fldr2/file.txt

Explanation:

• Insert the function to the end of ~/.bashrc file using the echo command
• The -p flag is for creating the nested folders, such as fldr2
• Update the ~/.bashrc file with the source command
• Use the mkfile function to create the file