# /proc is a pseudo-filesystem containing running process information and more.

# See the command line arguments that started the process
cat /proc/<pid>/cmdline

# See the process's environment variables
cat /proc/<pid>/environ

# See the process's status and usage information, such as CPU and memory
cat /proc/<pid>/status

# See every file the process has open
ls -l /proc/<pid>/fd

# Display some useful memory statistics, often used by programs like htop(1).
cat /proc/meminfo