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up vote 6 down vote favorite

I have a folder with three files:

$ ls
a  b  c

If I pipe the output of ls to wc, I get the right result:

$ ls | wc -l
3

However, when I specify the input to wc as the output of ls, I get extra text:

$ wc -l <(ls)
3 /dev/fd/63

Can anyone explain to me what is happening?

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1 Answer 1

up vote 13 down vote accepted

wc will tell you what file it's working on if it's able. With the first one with the pipe it's reading from stdin, not a file, so does not report a filename. The second one, however, you're using process substitution which presents the output of the command as a file, which wc reports. It reports on the file descriptor it was given from which to read.

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