If I type command on my terminal, I don't get command not found, and the exit code is 0. I assume that this means command actually does something on bash. Also, command -h returns:bash: command: -h: invalid optioncommand: usage: command [-pVv] command [arg ...]What is it used for?
What is 'command' on bash?
linux;bash;shell script
From help command:$ help commandcommand: command [-pVv] command [arg ...]    Execute a simple command or display information about commands.    Runs COMMAND with ARGS suppressing  shell function lookup, or display    information about the specified COMMANDs.  Can be used to invoke commands    on disk when a function with the same name exists.    Options:      -p    use a default value for PATH that is guaranteed to find all of      the standard utilities      -v    print a description of COMMAND similar to the `type' builtin      -V    print a more verbose description of each COMMAND    Exit Status:    Returns exit status of COMMAND, or failure if COMMAND is not found.As a more general note, rather than just using -h when you don't know what a command does, you should try:type -a commandWhich would in this case have told you it is a shell builtin.help commandis good for shell builtins.  For other commands (and also for shell builtins, actually), tryman somecommandAlso, -h is not necessarily the help option.  If you don't know what a command does, that may not be a safe assumption to make.  Safer is --help.somecommand --help(Common commands where -h is a valid option but does not mean help are ls, free, df, du.  All of these are informational only, but the assumption that -h will only ever mean help is a dangerous assumption.)