read keyboard input within a pipelined read loop

Question

In a script, I'd like to read a process output line by line, and get a confirmation from the user. So far I've done this:

mycommand-outputpiped | while (read line)
do
   read line
   #dostuff

   read confirm #oops -> this read the next item from the pipe, not the keyboard
done

So I tried to add:

read confirm < /dev/stdin

But it didn't change the thing, it still reads the next line from the pipe... How should I handle this?

Not related, but why do you have a read command in both the condition list and the loop body for the variable line? — chepner
– chepner, Commented Mar 5, 2013 at 17:33
I'm not sure about that - I believe the first checks there are still datas to read while the second reads the datas. I'm not sure how to clean it up — bagage
– bagage, Commented Mar 5, 2013 at 17:35

chepner · Accepted Answer · 2013-03-05 17:35:44Z

9

Both read commands are reading from the standard input stream inherited from the while loop. The following should work; your second read needs to read directly from the terminal, not /dev/stdin (which is the pipe).

mycommand-outputpiped | while read line
do
    # do stuff
    read confirm < /dev/tty
done

Note that there is just one read, in the while condition, and that it is not enclosed in parentheses (which would create a subshell, and line would only be available in that subshell, not the loop body).

answered Mar 5, 2013 at 17:35

chepner

538k77 gold badges594 silver badges746 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

read keyboard input within a pipelined read loop

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related