Why does “find . -name *.txt | xargs du -hc” give multiple totals?

Question

I have a large set of directories for which I\'m trying to calculate the sum total size of several hundred .txt files. I tried this, which mostly works:

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Answer 1

One alternate solution is to use bash for loop:

for i in `find . -name '*.txt'`; do du -hc $i | grep -v 'total'; done

This is good for when you need more control of what happens in the loop.

Answer 2

Another simple solution:

find . -name *.txt -print0 | xargs -0 du -hc

Answer 3

How about using the --files0-from option to du? You'd have to generate the null-terminated file output appropriately:

find . -name "*txt" -exec echo -n -e {}"\0" \; | du -hc --files0-from=-

works correctly on my system.

Answer 4

xargs busts its input into reasonable-sized chunks - what you're seeing are totals for each of those chunks. Check the man page for xargs on ways to configure its handling of input.

Answer 5

One alternate solution is to use awk:

find . -name "*.txt" -exec ls -lt {} \; | awk -F " " 'BEGIN { sum=0 } { sum+=$5 } END { print sum }'

Answer 6

The xargs program breaks things up into batches, to account for the limits due to the maximum length of a unix command line. It's still more efficient than running your subcommand one at a time but, for a long list of inputs, it will run the command enough times that each "run" is short enough that it won't cause issues.

Because of this, you're likely seeing one output line per "batch" that xargs needs to run.

Because you may find it useful/interesting, the man page can be found online here: http://unixhelp.ed.ac.uk/CGI/man-cgi?xargs

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One other thing to note (and this may be a typo in your post or my misunderstanding) is that you have the "*.txt" unescaped/quoted. Ie, you have

find . -name *.txt | xargs du -hc

where you probably want

find . -name \*.txt | xargs du -hc

The difference being that the command line may be expanding the * into the list of filenames that match... rather than passing the * into find, which will use it as a pattern.