strace

# pidof nginx
11853 11852

# strace -p 11853 -p 11852 -e trace=file -f
Process 11853 attached - interrupt to quit
Process 11852 attached - interrupt to quit
[pid 11853] stat("/var/www/html/kibanaindex.html", 0x7ffe04e93000) = -1 ENOENT (No such file or directory)
[pid 11853] stat("/var/www/html/kibana", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
^CProcess 11853 detached
Process 11852 detached