#!/bin/bash LF="/tmp/.lock" exec 200>"$LF" flock 200 echo "IN Lock" sleep 3 flock -u 200 exec 200>&-
#!/bin/bash CFL="./.count" LFL="./.count.lock" set +o noclobber exec 200>"$LFL" flock -x 200 trap 'exec 200>&-' EXIT touch "$CFL" wc -c < "$CFL" echo -n a >> "$CFL"