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I've noticed that the majority of Ubuntu help websites present apt commands in the following format:

sudo add-apt-repository ppa:[ppa-address]
sudo apt-get update
sudo apt-get install [application-name]

But I know that apt commands like this one work too:

sudo add-apt-repository ppa:[ppa-address] && sudo apt-get update && sudo apt-get install [application-name]

Is there a particular reason that most sites present in the first format? Are there known issues with chaining commands with &&, or to put it another way are there any benefits/drawbacks to using either method?

Further, other then loss of internet, are there any circumstances in which an apt command might fail?

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2 Answers 2

up vote 8 down vote accepted

Personally, I think sites list them one by one just for clarity. It's easier to run one at a time and understand what it does then it is to run, say 3, all at once.

I might point out too, not all sites do list commands one by one. For example, in the OMG Ubuntu article on installing Unity Tweak Tool the commands are listed as:

sudo add-apt-repository ppa:freyja-dev/unity-tweak-tool-daily  
sudo apt-get update && sudo apt-get install unity-tweak-tool  

It's also worth noting that && will only run the second or third (etc) command if the command before it returns exit status 0. In other words, the command after && will only be run if the command before && completes successfully.

If you'd like your string of commands to execute one by one no matter if any fail you would separate each command with ; instead of &&. For example:

sudo add-apt-repository ppa:[ppa-address] ; sudo apt-get update ; sudo apt-get install [application-name]  

(Of course, this wouldn't be a good thing to do when installing packages!)

There are a number of reasons why an apt command would fail:

  • apt-get install could fail for quite a few reasons, among them dependency issues, not enough disk space, no internet connection, or an old or malformed sources.list file.

  • apt-get update could fail for similar reasons, a malformed sources.list, no internet connection, a 404 PPA, etc.

These are just some of the things that would cause apt to fail, causing commands after && to not be run.

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It's presented in the first form because it's easier to read.

Plus, if you need to review your history for one of the commands, it's easier than picking one part of a long, complex command.

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1  
Another reason: it is easier to edit if you made a mistake. –  Lekensteyn May 9 '13 at 21:25

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