LinuxQuestions.org - [SOLVED] Bash string substitution (rsync exclude)

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vrltwe

05-15-2015 09:08 AM

Bash string substitution (rsync exclude)

I'm preparing a rsync script to backup from one machine to another through ssh. For this I'm successful with the following:

IP=150.163.49.15
ORIGIN=/home
DESTINATION=samba

rsync -avzP --exclude={cristiano,marcelo} root@$IP:$ORIGIN $DESTINATION/

I would like to improve it, moving the exclude part to a variable also. I've unsuccessfully tried this:

IP=150.163.49.15
ORIGIN=/home
DESTINATION=samba
EXCLUDE={cristiano,marcelo}

rsync -avzP --exclude=$EXCLUDE root@$IP:$ORIGIN $DESTINATION/

What is wrong with the EXCLUDE syntax?

warshall

05-15-2015 01:38 PM

Hi-

Your problem is that bash expands braces before variables. So your effective command line (the one rsync is actually getting) includes the literal string --exclude={cristiano,marcelo}, as opposed to the brace-expanded version of that, namely --exclude=cristiano --exclude=marcelo, which would be what you want.

You might want to use an array. I use zsh, not bash, but on my system, after

Code:

EXCLUDE=(cris marc)

Code:

${EXCLUDE/#/--exclude=}

expands to --exclude=cris --exclude=marc.

Hope this helps,

Andrew Warshall

jhekkanen

05-15-2015 01:51 PM

I'm assuming the Bash shell here. I'm not sure about all the details of
this but when you run the first command you are using brace expansion:

Code:

bash-4.2$ echo cmd --exclude={foo,bar}

cmd --exclude=foo --exclude=bar

Now when we introduce the variable, we can see where things go wrong:

Code:

bash-4.2$ EXCLUDE={foo,bar}

bash-4.2$ echo cmd --exclude=$EXCLUDE

cmd --exclude={foo,bar}

One option would be to use an array instead:

Code:

bash-4.2$ EXCLUDE=(foo bar)

bash-4.2$ echo cmd ${EXCLUDE[@]/#/--exclude=}

cmd --exclude=foo --exclude=bar

Keith Hedger

05-15-2015 07:15 PM

How about

Code:

EXCLUDE=$(echo --exclude={cristiano,marcelo})

echo rsync -avzP $EXCLUDE root@$IP:$ORIGIN $DESTINATION

gives

Code:

rsync -avzP --exclude=cristiano --exclude=marcelo root@150.163.49.15:/home samba

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