When I am writing a shell script, I have a problem about nested read as the following codes.
while read entry
do
IFS=' ' read -a array <<< "$entry"
read -p "Read from keyboard" keyin
case $keyin in
[a]* ) .....
.....
esac
done << file
I expected to read keyboard input but the 'read -p .... keyin' always read value from 'file'. Is anyone have idea about this? Any alternative method for me to read keyboard input in this situation?
Thanks.
Assuming you're using bash, you can arrange to read from different file descriptors:
while read -r -u 3 entry
do
IFS=' ' read -a array <<< "$entry"
read -p "Read from keyboard" keyin
case $keyin in
[a]* ) .....
.....
esac
done 3< file
The 3< redirects file as input to file descriptor 3; the -u 3 tells read to read from file descriptor 3. Thus, the outer loop is acting on lines from the file, leaving the inner read to act on keyboard input. The -r is modern but necessary to avoid unexpected behaviour (I learned to program without it; I resent needing to use it — the flag should be necessary to enable the modified behaviour).
Note that the original code in the question used << file; that starts a here document, but clearly wasn't what was intended since no body or end of the here document was shown.
bash? If so, say so (otherwise you might be asking about Korn shell orzshor Dash instead, or as well). Add the tag and say so in the question.