# Find and replace {} in sed

> There is an awkward gotcha when trying to find and replace the empty hash/object with sed from the command line.

- URL: https://velocitylabs.io/blog/2015/06/01/find-sed-empty-json-object/
- Published: June 1, 2015
- Author: Dave Tapley

### The problem

Replacing all instances of `vcr: {}` with `vcr: { record: :new_episodes }`, in all files below `spec/features`.

Normally this `find -exec` can come to the rescue, so a reasonable approach might be:

```
$ find spec/features/ -type f -exec sed -i 's#vcr: {}#vcr: { record: :new_episodes }#' {} \;
```

_Pro-tip: [change the delimiter](http://en.wikipedia.org/wiki/Regular_expression#Delimiters) to `#`_

Unfortunately we run in to trouble here: It just so happens that `{}` is the sequence find’s `-exec` switch uses to substitute in filenames.

Well, surely we can just escape the `{}` through find, right?

```
$ find spec/features/ -type f -exec sed -i 's#vcr: \{\}#vcr: { record: :new_episodes }#' {} \;`
sed: -e expression #1, char 45: Invalid content of \{\}
```

Not quite. Now the `\{\}` are being passed straight through to `sed`, including the `\`s, and unfortunately when sed sees escaped `{}`s it assumes them to be a [consecutive occurrence matcher](http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html#tag_09_03_06).

### The solution

Sometimes it’s best to just ditch `-exec` altogether, and use the ever versatile `xargs`:

```
$ find spec/features/ -type f -print0 | xargs -0 sed -i 's#vcr: {}#vcr: { record: :new_episodes }#'
```