gistfile1.txt

Regexp Lookaround Memo
======================

Lookahead
---------

```
❯ echo "hoge\nfuga\nhoge1\nfuga11\nhoge111\nfuga1111" | grep -P 'hoge(?=\d+)'
hoge1
hoge111
```

Negative Lookahead
------------------

```
❯ echo "hoge\nfuga\nhoge1\nfuga11\nhoge111\nfuga1111" | grep -P 'hoge(?!\d+)'
hoge
```

Lookbehind
----------

```
❯ echo "hoge\nfuga\n1hoge1\n11fuga11\n111hoge111\n1111fuga1111" | grep -P '(?<=\d)hoge'
1hoge1
111hoge111
```

Negative Lookbehind
-------------------

```
❯ echo "hoge\nfuga\n1hoge1\n11fuga11\n111hoge111\n1111fuga1111" | grep -P '(?<!\d)hoge'
hoge
```