Differences between current version and predecessor to the previous major change of IORedirectionNotes.
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| Newer page: | version 9 | Last edited on Saturday, July 14, 2007 11:55:01 pm | by LawrenceDoliveiro | |
| Older page: | version 8 | Last edited on Friday, July 13, 2007 1:07:23 pm | by BenStaz | Revert |
@@ -5,24 +5,25 @@
Firstly:
*sudo echo "#TEST REPOSITORY" >> /etc/apt/sources.list
-Results
in a "Permission denied error". This is because sudo spawns a new subshell and doesn't get
the ''>> /etc/apt/sources.list'' because it
is owned
by the parent
shell which
is you
.
-
+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'
-Commands are read
from string after the ''-c'' switch.
+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.
+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].
