The ps (process status) command is used to provide information about the currently running processes, including their process identification numbers (PIDs).

# To list every process on the system:
ps aux

# To list a process tree
ps axjf

# To list every process owned by foouser:
ps -aufoouser

# To list every process with a user-defined format:
ps -eo pid,user,command

# Exclude grep from your grepped output of ps.
# Add [] to the first letter. Ex: sshd -> [s]shd
ps aux | grep '[h]ttpd'