[SOLVED] Bash scripting: how to handle ampersand in a string for a positional parameter?

Hello all!

I'm really stumped on this. I've been having fun in my .bashrc with shell functions, including making one for a command "pull." But I'm having a hard time figuring out how to handle strings that include "&". For instance:

~]$ pull file domain.tr/1em121cww

works no problem.

But

~]$ pull file domain.tr/1em121cww&s3fs12kfs

does not.

I know the easy solution is on the command line to simply write

~]$ pull file "domain.tr/1em121cww&s3fs12kfs"

but it's not so easy when you have multiple filenames (making use of positional parameter "${@:2}").

Is there some other way of handling the ampersand in the shell function? I thought maybe with sed, but this ampersand creates an issue before the shell function runs. I also don't want to process (escape, quote) every bash input with ampersands - just what I use for the "pull" command.

Thanks a ton for any help!

Could you please explain the problem with multiple filenames?

Hi, thanks for the reply.

It's really a control operator issue. The issue I have is when I try to run the command on what is positional parameter and there is a character that is also a control operator - sorry if I wasn't clear on this in my first post. For instance:

~]$ dl song domain.tr/1em121cwws3fs12kfs

does work.

But

~]$ dl song domain.tr/1em121cww&s3fs12kfs

does not work.

In my .bashrc, I have this as part of a number of other lines:

dl() {

# First, we define the variables:
TorLaunch="/home/me/location1/tor-browser_en-US/Browser/start-tor-browser"
YtDL_base="youtube-dl --no-progress --console-title --ignore-errors --no-mtime"
YtDL_audio="-x --audio-format mp3 -f bestvideo[ext=mp4]+bestaudio[ext=m4a]/bestvideo+bestaudio -k --embed-subs"

    if [[ $1 == "song" ]]; then
while true; do
    read -p "(T)or download, (D)ownload, or (Q)ueue? : " tdq
    case $tdq in

        [Tt]* )
$TorLaunch &
until [ "$(proxychains4 curl -v --silent icanhazip.com  2>&1 | grep -i fail | wc -l)" -lt 1 ] || (( count++ >= 5 )) ;
do echo "Attempting to connect Tor..." && sleep 3;
done
proxychains4 -q $YtDL_base -o /home/me/location2/youtube-dl/'%(title)s'.flv $YtDL_audio "${@:2:99}"
break;;

        [Dd]* )

$YtDL_base -o /home/me/location2/youtube-dl/'%(title)s'.flv $YtDL_audio "${@:2:99}"
break;;

...and so on and so forth...

That issue occurs before the "dl" script code runs - ampersand is a special character, you need to escape it or wrap the input in single-quotes to have Bash treat it as a literal.

dl song 'domain.tr/1em121cww&s3fs12kfs'

(Unrelated to your issue, but instead of "${@:2:99}" you may prefer adding shift 1 after you've extracted the first argument, so you can then just use "$@" to get the rest.)

You need to quote the URL or escape the ampersand. Sorry.

@OP Please use [code] tags not [quote] tags when inserting code.

You could only solve this if you used a special shell that doesn't support background jobs (so &ampersand isn't special character) -- I don't know of such shell though.

Further to this suggestion:

(Unrelated to your issue, but instead of "${@:2:99}" you may prefer adding shift 1 after you've extracted the first argument, so you can then just use "$@" to get the rest.)

Assuming you wanted all but the first, obviously above is best suggestion, but the 99 is superfluous unless you are imagining 100s of parameters and you are limiting to less than 100??

Strange. "$@" should Do The Right Thing wrt double quotes - so I guess "${@:2:99}" should also do it.
- try the shift mentioned, then just "$@"
- try "$*" as well
and show us what it does.

edit:
bash version?
distro?

Ok, thanks a lot for this feedback! I'll give those a try. I was avoiding shift because it destroys the positional parameter, and I thought I'd preserve them because I'm a saving kind of guy. I'll give it a shot and report back.

Bash version: 5.0.11(1), Fedora 30.

If you're dealing with web stuff like that then you might want to put an en/decoder for URL stuff there anyway.
In case you want an upload function at one point, or something, too.