0

I would like to overwrite a Django/app/settings.py text file using the Linux terminal command printf.

The settings.py starts with docstrings comments, i.e. """some text""".
With printf the format is printf'some text' > filename.txt or printf"some text" > filename.txt.

Whichever " or ' is used the subsequent occurrence of the " or ' closes printf statement and breaks the desired run of the script.

For instance,

printf'

""" 
Django settings for hello_django project.

Generated by 'django-admin startproject' using Django 4.2.13.

For more information on this file, see
https://docs.djangoproject.com/en/4.2/topics/settings/

For the full list of settings and their values, see
https://docs.djangoproject.com/en/4.2/ref/settings/
"""
import os
from pathlib import Path

' > app/hello_django/settings.py

The echo command returns the same unsuccessful result.

Is it possible to achieve what I want using the printf or echo methods?

Some useful links with pointers that I have tried, write to file with echo/printf, How do I echo a lot of content in a bash script? and How to echo a bang!

Improve this question
2
  • And what is the unsuccessful result? I would expect what you show to be an error since that is not the format printf expects. You need a space after printf and before anything else. What you are showing is one huge command, so I would expect you to get a "no such command" error. Is that not what is happening? Commented Jul 8, 2024 at 14:26
  • You're trying to pass a 'quoted' argument to printf, but the text itself contains quotes (apostrophe characters). You must replace these with the sequence '\''. Close quote, backslash-quote, reopen quote. Or else, use a here-document. Commented Jul 9, 2024 at 7:19

2 Answers 2

Reset to default
2

Probably, a "here document" is what suits you need best; e.g.,

cat <<'END' >app/hello_django/settings.py
'''
...
'''
import os
...
END

Single quote END to protect the doc from any shell interpretation; otherwise, the shell will interpret backlash, interpolate variables, etc.

Improve this answer
1
  • Thank you GammaZoid. This is writing the complete text to the file as you have suggested. Commented Jul 9, 2024 at 8:28
1

Your approach would also work, but you need a space between the command, printf, and its arguments (the quoted string you want to print). So while this fails:

$ printf'Hello world\n' 
bash: printfHello world\n: command not found

This works:

$ printf 'Hello world\n' 
Hello world

Now, the problem with the internal quotes is different. You need to escape those. But only because you aren't using printf correctly. The whole point of printf is that you do not give it the string it is supposed to print directly but instead use a format string. In its simplest form, you would do something like printf '%s\n' "foo", and %s will be replaced by the argument you give it. In this case, foo.

So you could do something like this:

$ printf '%s' '

""" 
Django settings for hello_django project.

Generated by 'django-admin startproject' using Django 4.2.13.

For more information on this file, see
https://docs.djangoproject.com/en/4.2/topics/settings/

For the full list of settings and their values, see
https://docs.djangoproject.com/en/4.2/ref/settings/
"""

' > app/hello_django/settings.py

You can do this by typing out printf '%s' ' and then pressing Enter and pasting in the rest of the string. Or, perhaps more simply, store your string in a variable:

read -r -d '' var <<'EoF'

And then paste your text, and after the last line write EoF to close. It will look like this:

$ read -r -d '' var <<'EoF'
> """ 
> Django settings for hello_django project.
> 
> Generated by 'django-admin startproject' using Django 4.2.13.
> 
> For more information on this file, see
> https://docs.djangoproject.com/en/4.2/topics/settings/
> 
> For the full list of settings and their values, see
> https://docs.djangoproject.com/en/4.2/ref/settings/
> """
> import os
> from pathlib import Path
> 
> EoF

And you can now do (you need the \n because the shell will remove trailing newlines from variables):

printf '%s\n' "$var" > app/hello_django/settings.py
Improve this answer
8
  • Hi terdon, thank you for your very interesting suggestion. Though the printf fails when it arrived to this line SECRET_KEY = 'django-insecure-4$bee(yo0z6tg73+t_wqtmu*wry8e1+k3n69*_l+)in3mk=(#q' The error is bash: syntax error near unexpected token '(' I suspect that the '(' in question is bee(yo Commented Jul 9, 2024 at 8:29
  • @TommyGibbons sorry, but I have no idea which of the two approaches you used. And I hope you didn't just paste the real secret key openly on the internet, right? Commented Jul 9, 2024 at 8:36
  • While using the store string as a variable method was considered, this we found not to be useful in what we are doing. Still this is helpful to know, thank you. Commented Jul 9, 2024 at 8:37
  • paste the real secret key openly -- no no, we are just testing how best to automate the processes, checking as much as possible, all anomalies that we can think of . Thanks tedron Commented Jul 9, 2024 at 8:39
  • Apologies terdon, sausage finger in typing Commented Jul 9, 2024 at 8:42

You must log in to answer this question.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.