append content of a file to itself

cat file | tee >> file
The command `cat file >> file` failes with the following error message: cat: file: input file is output file `tee` is a nice workaround without using any temporary files.
Sample Output
echo "Just one line" >> file
cat file
> Just one line
cat file | tee >> file
cat file
> Just one line
> Just one line

By: GeckoDH
2009-07-30 07:34:03

What Others Think

Could you please tell us at least one reason we would duplicate a file in itself ?
CodSpirit · 667 weeks and 4 days ago
it looks like you mean to use > rather than >> here, because depending on when cat takes a break reading "file" and when the shell writes the incoming data you could end up with a file that just keeeeeeepppps groooooowing.
bwoodacre · 667 weeks and 2 days ago
For me its nice if I need to generate a test file with a, say, 10 chunks of identical 100,000 lines in it. So it's quicker to append the file to itself 10 times than write out 100,000 lines 10 times. But (ironically) this way didn't work for me (the file kept growing), so intermediate file is not a bad alternative. Maybe it's because the file is so gigantic, but oh well...
tefrak · 532 weeks ago

What do you think?

Any thoughts on this command? Does it work on your machine? Can you do the same thing with only 14 characters?

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