What does "< <(command args)" mean in the shell?

bash shell built-in
stib picture stib · Mar 14, 2010 · Viewed 17.5k times · Source

When looping recursively through folders with files containing spaces the shell script I use is of this form, copied from the internet:

    while IFS= read -r -d $'\0' file; do
      dosomethingwith "$file"        # do something with each file
    done < <(find /bar -name *foo* -print0)

I think I understand the IFS bit, but I don't understand what the '< <(...)' characters mean. Obviously there's some sort of piping going on here.

It's very hard to Google "< <", you see.

Answer

Josh Lee picture Josh Lee · Mar 14, 2010

<() is called process substitution in the manual, and is similar to a pipe but passes an argument of the form /dev/fd/63 instead of using stdin.

< reads the input from a file named on command line.

Together, these two operators function exactly like a pipe, so it could be rewritten as

find /bar -name *foo* -print0 | while read line; do
  ...
done

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