Why doesn't this wget download script work?

Question

I have the following lines in a .sh shell script:

wget -O discord.deb https://discordapp.com/api/download?platform=linux&format=deb
sudo dpkg -i discord.deb
rm -f discord.deb

For some reason, the script does not work. However, if I run the commands one-by-one manually, the code works as intended. What am I doing wrong?

I’m impressed that those lines work in an interactive shell. What shell do you use? — Jeff Schaller, Jan 08 '18 at 00:43
@Jeff My question and answer is shorter and simpler than that post. The point was to post a simple question and answer in one post. I don't think this deserves removal or anything. — Aaron Franke, Jan 08 '18 at 01:07
I'm not suggesting deletion; it's the same problem & solution, so identifying the duplicate is the right thing to do. https://unix.stackexchange.com/help/duplicates — Jeff Schaller, Jan 08 '18 at 01:45
I'm still curious how you ran it interactively and didn't get a background process. — Jeff Schaller, Jan 08 '18 at 01:45
I did get a background process, but it also posted terminal output, and if I manually waited for it to finish, then I could run dpkg and it would work. — Aaron Franke, Jan 08 '18 at 02:29

Aaron Franke · Accepted Answer · 2018-01-08T02:51:41.260

2

The problem is that the URL contains &, which tells the shell to run the wget command in the background. The dpkg command is then ran before the file is finished downloading.

To fix, simply add quotation marks around the URL:

wget -O discord.deb 'https://discordapp.com/api/download?platform=linux&format=deb'
sudo dpkg -i discord.deb
rm -f discord.deb

edited Jan 08 '18 at 02:51

answered Jan 07 '18 at 22:53

Aaron Franke

955

1

it's generally better to use single-quotes for fixed strings (to prevent interpolation), and double-quotes only where you want variable interpolation to occur. But make sure to check that the quotes you use don't also appear in the URL. BTW, sudo is needed to install the .deb file, but is not needed to rm it. – cas Jan 08 '18 at 01:02
Good points. I am used to using "" instead of '' in programming languages where '' denotes a character instead of a string. In your opinion, is it a significant enough of a difference to change the answer? – Aaron Franke Jan 08 '18 at 02:35
1

It makes no difference for this particular URL, but I'd change it. better to use the most appropriate quoting because someone will copy-paste-edit this answer with a URL where it does matter and then wonder why it doesn't work properly. BTW, this distinction between single and double quotes is pretty common - used in all bourne-type shells, perl, php, javascript and several others (see https://en.wikipedia.org/wiki/Comparison_of_programming_languages_(strings)) – cas Jan 08 '18 at 02:45

Why doesn't this wget download script work?

1 Answers1