read is not pausing to read

davegerdt · #1 (**permalink**) 04-05-2008

Can anyone tell me why this section of my script doesn't work? The script is designed to accept piped data, store it in a temporary location, and then prompt the user for their user name. It doesn't stop to read the username, however. It just finishes.

It is called like:

Code:

cat datafile | myscript

The script is as follows:

Code:

datafile1="data$$.dat"
datafile2="data$$2.dat"
pdffile="pdf$$.pdf"

# Store piped data
cat > $datafile1

# Prompt for username
echo "Enter your username:"

# Read username
read username

I also tried adding a loop trying to clear out the input data that I assumed was being left around, as shown in the following, but it didn't change anything.

Code:

# Store piped data
cat > $datafile1

while [ -z username ]
do
    read username
done

# Prompt for username
echo "Enter your username:"

# Read username
read username

What am I missing? Thanks for the help!

Perderabo · #2 (**permalink**) 04-05-2008

echo "enter your user name:" > /dev/tty
read username < /dev/tty

era · #3 (**permalink**) 04-06-2008

Just to expand on the answer a little bit, when you pipe something to a command, the shell changes the input file descriptor so the command is no longer reading from the terminal, but from the pipeline. There is no way you can get interactive user input from the default file descriptor, so you need to read it from somewhere else. /dev/tty is usually a good choice for reading from the terminal.

davegerdt · #4 (**permalink**) 04-07-2008

Thanks for the solution and explanation. Makes perfect sense.

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