View Source: IORedirectionNotes - Waikato Linux Users Group

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!Append to a file owned by root

In this example I will use the ''sources.list'' file that contains a list of the repositories from which we can get packages.

Firstly:

*sudo echo "#TEST REPOSITORY" >> /etc/apt/sources.list

results in a "Permission denied error". This is because the ''>> /etc/apt/sources.list'' redirection is processed by your shell _before_ spawning <tt>sudo</tt>, so it is trying to open the file with your (ordinary) user privileges, not root privileges.

Ways around this:

1)

*sudo bash -c 'echo "#TEST REPOSITORY" >> /etc/apt/sources.list'

The shell spawned by <tt>sudo</tt> reads its command from the string after the ''-c'' switch, so the redirection is done in a process which is already running as root.

2)

*echo "#TEST REPO" | sudo tee -a /etc/apt/sources.list

The 'tee' command reads from standard input and the ''-a'' switch appends it to the file. Again, the file is opened by the process spawned by <tt>sudo</tt>, which is running as root.

3)

*sudo tee -a /etc/apt/sources.list <<< "#TEST REPO"

An alternative formulation of 2), using a [HereString|HereStrings].

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Last edited on Saturday, July 14, 2007 11:55:01 pm by LawrenceDoliveiro

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