Using variables as function arguments in Bash

Question

I have a simple question about using variables as inputs to a command in a Bash script. I would like to write a script that automatically copies certain contents of a directory, foo, to an embedded computer connected over ssh in another directory, bar.

In other words, I want to turn the following command into an easier to maintain script:

ssh -r /foo/{file1,file2,dir1,*.h,*.hpp,*.c,*.cpp} [email protected]:~/bar

So far, I have the following:

#!/bin/bash

SOURCE='/foo';
FILES='{file1,file2,dir1,*.h,*.hpp,*.c,*.cpp}';
DESTINATION='[email protected]:~/bar';

set -x
scp -r $SOURCE/$FILES  $DESTINATION
set +x

However, this gets executed as:

ssh -r '/foo/{file1,file2,dir1,*.h,*.hpp,*.c,*.cpp}' '[email protected]:~/bar'

I'm sure I am using the wrong kinds of quotes or parenthesis somewhere, but I feel like I've tried everything. Thanks to anyone who can help a newbie out. :)

devnull · Accepted Answer · 2014-01-15 07:19:17Z

2

The manual would tell you that Brace expansion is performed before any other expansions ...

I don't think that you have any option but to use eval here if you want to make use of variables in the command:

SOURCE='/foo';
FILES='{file1,file2,dir1,*.h,*.hpp,*.c,*.cpp}';
FILELIST="$(eval echo "${SOURCE}"/"${FILES}")"

and later say:

scp -r "$FILELIST"  $DESTINATION

answered Jan 15, 2014 at 7:19

devnull

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1 Comment

Michael Darling Over a year ago

Well you certainly got me closer to a solution. With your approach the FILELIST got expanded, but the arguments to scp were still appearing inside single quotes so in my case (where /foo is the current directory ., and DESTINATION is referencing the home directory, ~, those symbols weren't getting parsed. I had to modify your solution to read scp -r $(eval echo "$FILELIST") $(eval echo $DESTINATION) to work. Thanks for your help!

John1024 · Accepted Answer · 2014-01-15 07:33:31Z

1

If you put the braces or the *s inside quotes they will not be expanded by the shell. So, use:

scp -r "$SOURCE/"{file1,file2,dir1,*.h,*.hpp,*.c,*.cpp}  $DESTINATION

If you really want to define the file list before calling scp, then use a bash array:

filelist=( "$SOURCE/"{file1,file2,dir1,*.h,*.hpp,*.c,*.cpp} )

scp -r "${filelist[@]}" $DESTINATION

Here, filelist is an array and "${filelist[@]}" is bash's special incantation to return each filename in the list as a separate argument to scp.

edited Jan 15, 2014 at 7:33

answered Jan 15, 2014 at 7:20

John1024

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1 Comment

Michael Darling Over a year ago

I ended up using something closer to devnull's approach, but thanks for your help and teaching me something new about bash arrays! =)

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