CODEWITHSUNDEEP
bashshellposix
Daniel Kaplan
Daniel Kaplan

Reputation: 67310

Run multiple commands, but run the last one in the background

I have 4 commands I want to run:

sudo mkdir -p /data/db && \
sudo chmod 755 /data/db && \
sudo chown -R addison.pan: /data && \
mongod &

I only want to run mongod in the background if the other 3 above it succeed. But when I type this into bash, it runs the whole thing as one background task. How do I only make the mongod run in the background, and only if it gets to it?

Upvotes: 3

Views: 86

Answers (4)

William Pursell
William Pursell

Reputation: 212208

Be explicit. There's no need to try to abuse the syntax to use a short-circuit:

if \
    sudo mkdir -p /data/db \
    && sudo chmod 755 /data/db \
    && sudo chown -R addison.pan: /data
then
    mongod & 
fi

Upvotes: 2

bignose
bignose

Reputation: 32279

To run one or more commands in a separate process, enclose that series of commands in parentheses. As specified in the Single Unix Specification, §2.9.4 “Compound Commands”:

( compound-list )

Execute compound-list in a subshell environment […]

To group one or more commands in the same shell process, enclose that series of commands in curly braces:

{ compound-list ; }

Execute compound-list in the current process environment. […]

That's true for any POSIX shell (so it also works in Bash).

So your example can be changed to:

sudo mkdir -p /data/db && \
sudo chmod 755 /data/db && \
sudo chown -R addison.pan: /data && \
( mongod & )

That may be good because you want the mongod process separated. On the other hand, a more general answer would be to group the list of commands within the same shell process:

sudo mkdir -p /data/db && \
sudo chmod 755 /data/db && \
sudo chown -R addison.pan: /data && \
{ mongod & }

Both these are described in the above documentation references.

Upvotes: 3

nbari
nbari

Reputation: 26905

You could run multiple commands within sudo, for example:

sudo sh -c 'mkdir -p /data/db && chmod 755 /data/db && chown -R <user>: /data' \
&& mongod &

Upvotes: 0

abelenky
abelenky

Reputation: 64672

Use parens:

sudo mkdir -p /data/db && \
sudo chmod 755 /data/db && \
sudo chown -R addison.pan: /data && \
(mongod &)

Upvotes: 0

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