command type

info

1. display information about command type

   1. an executable program

       like all those tiles we saw in /urs/bin
      
       programs can be
       1. compiled binaries such as programs written in c or c++
       2. programs written in scripting languages such as the shell, perl, python, ruby
      

   2. a command built into the shell itself

       bash provides a number of commands internally called shell builtins
      
       the `cd` command is a shell builtin
      

   3. a shell function

       these are miniature shell scripts incorporated into the env
      
       $ fac() { (echo 1; seq $1) | paste -s -d\* | bc; }
       $ fac 5
       120
      

   4. an alias

       commands that you can define yourselves
       built from other commands
      
       $ alias l='ls -1 --group-directories-first'
      

usage

1. builtin

        $ type -a pwd
        pwd is a shell builtin
        pwd is /bin/pwd
   

2. function

        $ type -a fac
        fac is a function
        fac ()
        {
            ( echo 1;
            seq $1 ) | paste -s -d\* | bc
        }
   

3. alias

        $ type -a l
        l is aliased to `ls -1 --group-directories-first`