在bash中，循环并发送命令以执行

Question

Im trying to execute a program and send it commands based on a file that Im reading but as soon as I send the command the loop stop..it must be related to pipes but I would appreciate if someone could explain how they work

Code:

function setValue{

 echo "$1" > &9 
}

mkfifo program.fifo

./program
exec 9 > program.fifo

while read value
do 

setValue $value

done < file.csv

file.csv has 8000 rows, but the program stops after the first line...and finishes the execution without looping on any more lines of the csv

Answer 1

通过使管道保持打开状态以读取循环，在读取第一行之后循环不会结束，它可以继续到文件末尾：

exec 9 <> program.fifo

Answer 2

What is reading from program.fifo ? If there is no process that is reading it, then your script is blocked trying to write. That write will not complete until some process is reading the fifo.

Answer 3

My guess is that the code you aren't showing us in the while loop is consuming all of its stdin, which is the same as the input of the while loop. The cleanest way to avoid that is to ensure that the commands in the loop are not reading from the same file as the loop. There are many ways to do that; I like:

while read value; do {
   commands
} < /dev/null
done  < file.csv