Work with named pipe
In the i-pipex1 example, the cat command sets up a message handler routine and the echo command acts as the requestor.
i-pipex1
# Named Pipe Example 1.
#
# Create named pipe...
mknod trypipe p
# Open named pipe and read message...
cat trypipe &
# Write message...
echo "This is a message!" > trypipe
# Delete pipe...
rm trypipe
To try this example, run the shell script, i-pipex1. This script performs the following actions:
1. The mknod command creates a named pipe called trypipe.
2. The cat command opens trypipe for reading. It blocks because trypipe has not yet been opened for writing. Notice that an ampersand (&) is present at the end of the cat command; this runs the cat command as a background process.
3. The echo command opens trypipe for writing and writes a message. The cat command, blocked until now, resumes execution, and the message appears on the display.
4. The rm command deletes trypipe.
#! /usr/bin/env bash
pipe=/path/to/pipe
[ -p "$pipe" ] || mkfifo -m 0600 "$pipe" || exit 1
while :; do
while read -r cmd; do
if [ "$cmd" ]; then
printf 'Running %s ...\n' "$cmd"
# sh -c "$cmd" sh
fi
done <"$pipe"
done
And here: https://www.linuxjournal.com/content/using-named-pipes-fifos-bash