Bash quoting of current path (pwd)

Question

I have encountered a most annoying problem that occurs on the PWD variable when the current path includes a space. My code looks somewhat like this:

mycommand |sed -E '
 s|mystuff|replacement| ;
 s|'$(pwd)'|replacement| ;
 '

This works great, unless the current path contains a space character. If it does, $(pwd) is expanded to

'mypath/with space'

instead of just

mypath/with space

This cause the sed expression to be messed up (because of the extra quotes):

sed: 1: "s|mypath/with": unterminated substitute pattern

I have noticed that it doesn't help to expand pwd like this: ${PWD//\'/}.

How can this be solved?

Is that really the command? Variables aren't expanded inside single-quotes, so I can't see how $(pwd) in the above would be getting expanded at all. — Laurence Gonsalves, Sep 07 '09 at 09:54
Thanks for pointing that out. I've added the missing quotes. — Ludvig A. Norin, Sep 07 '09 at 09:57
Have you tried using the equivalent environment variable ($PWD) instead of command substitution to see if it makes a difference? — Dennis Williamson, Sep 07 '09 at 10:42
As is explained in the question, yes. The contents of the variable is what is returned by the pwd command (including the single-quotes). — Ludvig A. Norin, Sep 07 '09 at 11:15

mouviciel · Accepted Answer · 2009-09-07T11:48:25.810

6

Replace single quotes by double quotes and replace quotes with backquotes around pwd:

mycommand | sed -E "
 s|mystuff|replacement| ;
 s|`pwd`|replacement| ;
"

Double quotes allow expansion of variables and backquoted commands.

edited Sep 07 '09 at 11:48

answered Sep 07 '09 at 10:11

mouviciel

1

You used a variable where the OP used command substitution, but it works if you change it to match (or if you use it as is in the appropriate situation). – Dennis Williamson Sep 07 '09 at 10:23
This will not work, as $(pwd) will be expanded to 'mypath/with space', which won't match in the sed expression. If I used ${PWD//\'/} this would work, though. – Ludvig A. Norin Sep 07 '09 at 10:24
@Ludvig: I'm not getting the single quotes when I try this. – Dennis Williamson Sep 07 '09 at 10:29
The point about command substitution instead of variable substitution is correct. I update my answer accordingly. – mouviciel Sep 07 '09 at 11:47
1

To be clear, the solution is to use double-quotes around the sed expression, and to use the PWD environment variable, removing single-quotes, instead of the pwd builtin which will produce single-quotes still: mycommand | sed -E " s|${PWD//\'/}|replacement " – Ludvig A. Norin Sep 07 '09 at 13:58

score 1 · Answer 2 · edited Sep 09 '22 at 19:50

1

Replace

'$(pwd)'

with

'"$(pwd)"'

It would look like this then:

mycommand | sed -E '  
 s|mystuff|replacement| ;  
 s|'"$(pwd)"'|replacement| ;  
 '

edited Sep 09 '22 at 19:50

Peter Mortensen

answered Sep 07 '09 at 10:14

Atmocreations

You have a double quote out of place in the line following "with" – Dennis Williamson Sep 07 '09 at 10:26
oh well... may i have an old version of sed? i don't even have the option -E, only -e. I've checked using the following command: echo PART1$(pwd)PART2| sed -e 's|PART1|replaced| ; s|'"$(pwd)"'|PATH|;' ; and the output is replacedPATHPART2 – Atmocreations Sep 07 '09 at 10:31
No, compare the line I mentioned with the next-to-last line. It's just a typo. – Dennis Williamson Sep 07 '09 at 10:33

2 Answers2