Netcat bash daemon example
#!/bin/bash
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# A simple example of a daemon done with netcat in bash
# netcat executable may be called nc, netcat or ncat depending on your distribution
# here I'm using openbsd variant of netcat
# ~]$ nc -h 2>&1 | head -1
# OpenBSD netcat (Debian patchlevel 1)
# Other flavours: gnu netcat, nmap netcat
LISTENPORT=1234
# Open a fifo socket
MYFIFO=$(mktemp -u)
mkfifo $MYFIFO
# netcat will save all output to socket. spawn in background
nc -4 -l -d -n -k $LISTENPORT > $MYFIFO &
# there are for sure better way to get nc pid. This is just a raw example
NCPID="$(jobs -l | grep -w nc | awk '{print $2}')"
# n: add line numbering to output
n=0
INPUT="x"
while ( [ "$INPUT" != "q" ] ); do {
read INPUT < $MYFIFO && echo "$n: $INPUT"
# do here other code based on input received
# rotate line numbering
n=$(( ( n+1 ) % 10 ))
}
done
# kill background nc if still exist
ps h -p $NCPID -o comm | grep -qw nc && kill $NCPID
[ -p $MYFIFO ] && rm -f $MYFIFOINFO