How to create a new background process in a KSH "while read" loop?
- by yael
The following test script has a problem. When I add the line (sleep 5 ) & in the script then the "while read" loop does not read all lines from the file, but only prints the first line.
But when I remove the ( sleep 5 ) & from the script, then the script prints all lines as defined in the file.
Why the ( sleep 5 ) & causes this?
And how to solve the problem? I want to create a new process (for which the sleep is just an example) in the while loop:
$ more test
#!/bin/ksh
while read -r line ; do
echo Read a line:
echo $line
( sleep 5 )&
RESULT=$!
echo Started background sleep with process id $RESULT
sleep 1
echo Slept for a second
kill $RESULT
echo Killed background sleep with process id $RESULT
done < file
echo Completed
On my Linux, when using the following contents of file:
$ more file
123 aaa
234 bbb
556 ccc
...running ./test just gives me:
Read a line:
123 aaa
Started background sleep with process id 4181
Slept for a second
Killed background sleep with process id 4181
Completed
