How do I use a Bash variable (string) containing quotes in a command?

Question

Failing, simplified example:

FLAGS='--archive --exclude="foo bar.txt"'
rsync $FLAGS dir1 dir2

I need to include the quotes as if the command was like this:

rsync --archive --exclude="foo bar.txt" dir1 dir2

Related: Pass arguments to function exactly as-is. – May 30 '18 at 16:18 — , May 30 '18 at 16:18

Gordon Davisson · Accepted Answer · 2011-11-24T16:25:35.040

86

Short answer: see BashFAQ #50 ("I'm trying to put a command in a variable, but the complex cases always fail!").

Long answer: Putting commands (or parts of commands) into variables and then getting them back out intact is complicated. When the shell expands a variable on the command line, if the variable was in double-quotes it's not parsed; if it was not in quotes, spaces in it are parsed as argument breaks, but quotes and escape are not parsed. In either case, putting quotes in the variable's value does nothing useful.

Usually, the best way to do this sort of thing is using an array instead of a simple text variable:

FLAGS=(--archive --exclude="foo bar.txt")
rsync "${FLAGS[@]}" dir1 dir2

edited Nov 24 '11 at 16:25

answered Nov 24 '11 at 06:38

Gordon Davisson

34,729

4

Holy Jezus it works! – Slawomir May 02 '19 at 18:11
Thanks! Anything without intermediate variable (and not modifiying the command itself like with eval prefix) is impossible, right? – mvorisek Nov 15 '20 at 23:18
1

@mvorisek If I understand what you mean (using a non-array variable, and no eval or equivalent), then it's impossible. – Gordon Davisson Nov 16 '20 at 05:17

score 8 · Answer 2 · edited May 23 '17 at 12:41

8

eval is another option:

$ x="'a b'"
$ printf '%s,%s' $x
'a,b'
$ eval printf '%s,%s' $x
a b

See also:

edited May 23 '17 at 12:41

Community

1

answered Jul 05 '15 at 08:26

Ciro Santilli OurBigBook.com

11,570

score 4 · Answer 3 · answered Sep 03 '20 at 12:36

4

Alternatively, you can create an alias for your command:

alias myrsync='rsync --archive --exclude="foo bar.txt"'
myrsync dir1 dir2

answered Sep 03 '20 at 12:36

cbix

141

alias myrsync="rsync $FLAGS" is more correct answer to the specific question IMO – Martian2020 Dec 21 '22 at 03:59

score 0 · Answer 4 · answered Nov 14 '20 at 02:19

0

One option is to use eval to parse into an array. Obviously this will let whoever controls the string doing whatever they want.

FLAGS='--archive --exclude="foo bar.txt"'
eval "FLAGS=($FLAGS)"
rsync "${FLAGS[@]}" dir1 dir2

answered Nov 14 '20 at 02:19

Kevin Cox

1,484
1
9
12

score 0 · Answer 5 · answered Jan 20 '22 at 14:33

As stated by @cbix, using an alias is a nice solution in this case.

Don't forget to allow aliases expansion in scripts by using the line

shopt -s expand_aliases

As explained here https://www.thegeekdiary.com/how-to-make-alias-command-work-in-bash-script-or-bashrc-file/ it is stated in the man page of bash:

Aliases are not expanded when the shell is not interactive, unless the expand_aliases shell option is set using shopt

score -2 · Answer 6 · answered Nov 24 '11 at 17:49

-2

I don't see the problem :

$ FLAGS='--archive --exclude="foo bar.txt"'
$ echo $FLAGS
--archive --exclude="foo bar.txt"

Maybe you need to quote again the value :

$ rsync "$FLAGS" dir1 dir2

answered Nov 24 '11 at 17:49

Franck Lefort

75

5

echo isn't showing what you think it is. Try printargs() { printf "'%s' " "$@"; echo; }; printargs $FLAGS; printargs "$FLAGS" to see why neither of these options work. – Gordon Davisson Nov 25 '11 at 02:25
@GordonDavisson But printargs() prints same output if no arguments or if one empty string argument. – JohnMudd Dec 17 '19 at 13:51

How do I use a Bash variable (string) containing quotes in a command?

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