Forever, by default, will put logs into a random file in ~/.forever/
folder.
You should run forever list
to see the running processes and their corresponding log file.
Sample output
>>> forever list
info: Forever processes running
data: uid command script forever pid logfile uptime
data: [0] 6n71 /usr/bin/node app.js 2233 2239 /home/vagrant/.forever/6n71.log 0:0:0:1.590
However, it's probably best to specify with -l
as mentioned by bryanmac.