Understanding the different prompts on the command line
Comparing prompts
The “prompt” is the thing to the left of your cursor. Based on what prompt you see, you’re allowed to do different things. Maybe you’re able to run command line commands, or Python commands, or SQL commands.
But you can’t use them all at once, they all need different prompts! Think of it as getting into Python mode, or SQL mode, or command line mode.
Command line
If you’re in the command line prompt, it could look like just about anything. It’s usually pretty long, though, and usually has your username in it:
soma@skatert ~ % pwd
/Users/soma
soma@skatert ~ %This is what comes up by default when you open Cmder or Terminal, and it also usually comes up when you quit Python or Postgres (see below). You can run commands like ls or cd here.
Python interactive prompt
If you’re in the Python interactive prompt (aka the Python REPL), each line will start with a lot of greater-than symbols.
>>> print("hello")
hello
>>> If you’re here, you can run Python one line at a time. Running Python one line at a time isn’t very useful, though, and if you end up there it’s usually by accident!
Postgres client
If you’re in the Postgres (or PostgreSQL) client, each line will start with your username (or postgres) and an =#.
soma=# \l
List of databases
Name | Owner | Encoding | Collate | Ctype | Access privileges
-----------+-------+----------+---------+-------+-------------------
postgres | soma | UTF8 | C | C |
soma | soma | UTF8 | C | C |
template0 | soma | UTF8 | C | C | =c/soma +
| | | | | soma=CTc/soma
template1 | soma | UTF8 | C | C | =c/soma +
| | | | | soma=CTc/soma
(4 rows)
soma=# The PostgreSQL prompt is good for running SQL commands. Yes, there are ways of doing it that don’t involve the command line, but yes, we’re hiding it from you right now.
None of those!
If you see some other sort of prompt – maybe >dquote or >quote or >bquote – or nothing at all is happening when you type, slam Ctrl+C and try to escape from whatever you’re in. It will… maybe work.
Fun and confusing, right?
Getting into (and out of) the Python REPL
When you type python --version on the command line it shows you the version of Python.
$ python --version
Python 3.10.0If you just type python, though, something totally different happens!
soma@skatert ~ % python
Python 3.10.0 (default, Oct 27 2021, 12:08:22) [Clang 12.0.0 (clang-1200.0.32.29)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> This is called the interactive prompt or the REPL or probably a hundred other things. It’s a place you can run Python code, one line at a time.
>>> 2+2
4
>>> 0.1 + 0.2
0.30000000000000004
>>> But the thing is, you can only run Python code in here. Nothing else! If you try to use cd or ls or any of that, you’re out of luck and it’ll just scream at you. It only knows Python!
>>> ls
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'ls' is not definedTo exit the REPL, you’ll try to type exit.
>>> exit
Use exit() or Ctrl-D (i.e. EOF) to exitExiting the Python REPL
To actually exit the Python interactive prompt, you’ll need to type exit() instead.
>>> exit()
$And then you’ll be back at your normal shell!
Getting into (and out of) the Postgres prompt
If you want to find the version of postgres you’re using, you can use psql --version.
$ psql --version psql (PostgreSQL) 14.0
If you type psql, though, you’ll (maybe, possibly) end up at the Postgres prompt. You might also type psql -U postgres to get here, I dunno.
```$ psql psql (14.0) Type “help” for help.
postgres=#
When you're here, you can only run postgres commands!
### Exiting the Postgres promnpt
To exit the postgres prompt, you can type `\q`. It'll take you right back to the command line.
soma@skatert ~ % psql psql (14.0) Type “help” for help.
soma=# soma@skatert ~ % ```
I swear sometimes exit works but I honestly don’t know anything.
Other prompts (that aren’t prompts)
If you see dquote> or bquote> or quote> or anything like that, it isn’t actually a prompt! It’s a command that never finished getting typed.
Check out this page for a fix or press ctrl+C.