Determine if only one instance is running: Difference between revisions

fcntl based:

Unix Domain Socket based:

<lang nim>import options, os, std/monotimes

from net import newSocket, bindUnix

from nativesockets import AF_UNIX, SOCK_DGRAM, IPPROTO_IP

from posix import EADDRINUSE

const sockAddr = "\0com.myapp.sock" # Linux will delete this when the application ends

# notice the prefixed null byte, it's the Linux abstract namespace

proc server()=

echo "Unique instance detected"

proc client()=

echo "Duplicate instance detected"

when isMainModule:

var

sock = newSocket(AF_UNIX, SOCK_DGRAM, IPPROTO_IP)

isUnique: Option[bool]

try:

sock.bindUnix(sock_addr)

is_unique = some true

except OSError:

if cint(osLastError()) == EADDRINUSE:

isUnique = some false

else:

raise getCurrentException()

if unlikely is_unique.isNone:

echo "Error detecting uniqueness" # unreachable

else:

if isUnique.unsafeGet():

server()

else:

client()</lang>