[linux] Total size of the contents of all the files in a directory

du is handy, but find is useful in case if you want to calculate the size of some files only (for example, using filter by extension). Also note that find themselves can print the size of each file in bytes. To calculate a total size we can connect dc command in the following manner:

find . -type f -printf "%s + " | dc -e0 -f- -ep

Here find generates sequence of commands for dc like 123 + 456 + 11 +. Although, the completed program should be like 0 123 + 456 + 11 + p (remember postfix notation).

So, to get the completed program we need to put 0 on the stack before executing the sequence from stdin, and print the top number after executing (the p command at the end). We achieve it via dc options:

  1. -e0 is just shortcut for -e '0' that puts 0 on the stack,
  2. -f- is for read and execute commands from stdin (that generated by find here),
  3. -ep is for print the result (-e 'p').

To print the size in MiB like 284.06 MiB we can use -e '2 k 1024 / 1024 / n [ MiB] p' in point 3 instead (most spaces are optional).