How to run multiline bash commands as sudo

Question

I am trying to launch an application that needs many switches in order to operate so I have multi lined them using the \ operator. Now I need to run this application as well as some exports to be ran as another user.

What I am currently attempting to do is

sudo -u user bash <<EOF
export AUDIO_DRV=alsa
export ...
exec application --switch1 \
    --switch2 \
    --switch3 \
    --switch4 \
    ... \
    "$@"
EOF

I would run sudo myscript.sh so that root may setup a few things before it drops privileges to run the main application. The problem is that the multi line switches are not all being passed to the application causing unexpected results.

Is there any way to make this work as clean as this would of been or am I stuck appending all the switches to one line in order for it to work?

that other guy · Accepted Answer · 2015-11-13T00:26:42.620

Self-contained examples are a great way to see what goes wrong and why.

Here's a self-contained example that demonstrates that your use of multiline arguments is fine:

touch myfile.txt
bash << eof
find . \
  -name '*.txt' \
  -type f
eof

Here's another self-contained example that demonstrates that your use of "$@" is wrong:

touch foo bar
set -- foo bar
bash << eof
  ls "$@"
eof

Expected result is bar foo (because ls lists two files), but actual result is ls: cannot access foo bar: No such file or directory (because ls tries to list one).

This is because the $@ is expanded before being passed to bash, so instead of the magic quoting behavior of "$@" you just get $@ replaced by the concatenation of the variables between literal double quotes.

You should instead pass the parameters to bash and have bash expand them:

touch foo bar
set -- foo bar
bash -s -- "$@" << eof
  ls "\$@"
eof

The "$@" was exactly the problem. Thanks! The only reason I thought it was the multi line arguments was because the application was printing messages about not receiving one of the required switches to operate or so I thought. Thanks! — randy newfield, Nov 13 '15 at 00:18
@randynewfield I missed the `--` that tells bash not to interpret them as its own options — that other guy, Nov 13 '15 at 00:26

score 0 · Answer 2 · edited May 23 '17 at 10:27

0

I think here is answer for that: how to run two commands in sudo?

in general its:

sudo -s — 'whoami; whoami'

 sudo -u user -s -- ' \
    whoami; \
    whoami; \
    "$@"
'

edited May 23 '17 at 10:27

Community

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answered Nov 12 '15 at 23:57

Anar Alishov

26
2

So you are saying there is no way to cleanly present multiple switches for a single application to sudo? – randy newfield Nov 13 '15 at 00:02
You don't need the backslashes inside the quoted string. – chepner Nov 13 '15 at 00:11
@chepner is right do not need black slashes, need to put semicolon after each command – Anar Alishov Nov 13 '15 at 00:29

Denio Mariz · Answer 3 · 2015-11-14T18:16:15.220

0

You can write the command in a file and execute them as a script using sudo. The script does not need to contain the multi line escape "\" -- you can write the entire command in just one line if you want.

Also, you can build a function and execute the function using sudo.

MyFuncion(){
    application --switch1 --switch2 --switch3 --switch4 "$@"
    cmd 2
    # etc
}
sudo MyFunction

edited Nov 14 '15 at 18:16

answered Nov 14 '15 at 18:10

Denio Mariz

1,065
1
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How to run multiline bash commands as sudo

3 Answers3