Bash user prompt while reading file

Question

I am trying to create a user prompt while reading a file a line by line in Bash. The idea is for me to plot various files one-by-one using Gnuplot. Here is what I have:

#!/bin/bash
echo "Enter filename that contains the filenames:"
read fname
xr="[1e8:1e20]"
yr="[1:1e13]"

while read line
do
  echo -e "reset\nset log\nset xrange$xr\nset yrange$yr\nset xlabel \"Frequency [Hz]\"\nset ylabel \"F_{/Symbol n} [Jy Hz]\"\nset key top left\nplot \"$line.dat\" u 3:(\$3*\$4)*1e26 w l ti \"$line^o\" \n"> plt.gp
gnuplot plt.gp
done < $fname

I would like to enter a user input/"continue?" type thing before "gnuplot plt.gp" command, because at the moment it just plots everything rapidly and then exits. The standard read -p command does not work here. I read somewhere I may need to use file descriptor exec 5 command, but I don't understand. Thanks.

@Vlad Lazarenko: Thanks. Could you please give me a few more details how I would use that? I searched around read another_line, but could not find any examples. — Omar
– Omar, Commented Dec 7, 2011 at 21:17

user405725 · Accepted Answer · 2011-12-07 21:48:23Z

8

#!/bin/bash

read -p 'Enter filename that contains the filenames: ' fname

xr="[1e8:1e20]"
yr="[1:1e13]"

while read line
do
    echo -e "reset\nset log\nset xrange$xr\nset yrange$yr\nset xlabel \"Frequency [Hz]\"\nset ylabel \"F_{/Symbol n} [Jy Hz]\"\nset key top left\nplot \"$line.dat\" u 3:(\$3*\$4)*1e26 w l ti \"$line^o\" \n"> plt.gp
    gnuplot plt.gp

    read -p 'Do you want to continue? [Y/n]: ' want_to_continue </dev/tty
    case "${want_to_continue}" in
    Y|y)
        continue
        ;;
    *)
        echo "OK. Bye!"
        break
        ;;
    esac
done < ${fname}

answered Dec 7, 2011 at 21:48

user405725

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1 Comment

Omar Over a year ago

Thank you for such a complete example. It works perfectly and I have learnt a few more things about Bash scripting :-)

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