mirror of
https://github.com/Brandon-Rozek/website.git
synced 2024-11-28 22:47:07 -05:00
66 lines
No EOL
1.6 KiB
Markdown
66 lines
No EOL
1.6 KiB
Markdown
---
|
|
date: 2022-12-18 12:55:32-05:00
|
|
draft: false
|
|
math: false
|
|
medium_enabled: true
|
|
medium_post_id: 9801b2556737
|
|
tags: []
|
|
title: Capturing Quoted Strings in Sed
|
|
---
|
|
|
|
*Disclaimer: This posts assumes some knowledge about regular expressions.*
|
|
|
|
Recently I was trying to capture an HTML attribute in `sed`. For example, let's say I want to extract the `href` attribute in the following example:
|
|
|
|
```
|
|
<a href="https://brandonrozek.com" rel="me"></a>
|
|
```
|
|
|
|
Advice you commonly see on the Internet is to use a capture group for anything between the quotes of the href.
|
|
|
|
In regular expression land, we can represent anything as `.*` and define a capture group of some regular expression `X` as `\(X\)`.
|
|
|
|
```bash
|
|
sed "s/.*href=\"\(.*\)\".*/\1/g"
|
|
```
|
|
|
|
What does this look like for our input?
|
|
|
|
```bash
|
|
echo \<a href=\"https://brandonrozek.com\" rel=\"me\"\>\</a\> |\
|
|
sed "s/.*href=\"\(.*\)\".*/\1/g"
|
|
```
|
|
|
|
```
|
|
https://brandonrozek.com" rel="me
|
|
```
|
|
|
|
It matches all the way until the second `"`! What we want, is to not match *any* character within the quotations, but match any character that is not the quotation itself `[^\"]*`
|
|
|
|
```bash
|
|
sed "s/.*href=\"\([^\"]*\)\".*/\1/g"
|
|
```
|
|
|
|
This then works for our example:
|
|
|
|
```bash
|
|
echo \<a href=\"https://brandonrozek.com\" rel=\"me\"\>\</a\> |\
|
|
sed "s/.*href=\"\([^\"]*\)\".*/\1/g"
|
|
```
|
|
|
|
```
|
|
https://brandonrozek.com
|
|
```
|
|
|
|
Within a bash script, we can make this a little more readable by using multiple variables.
|
|
|
|
```bash
|
|
QUOTED_STR="\"\([^\"]*\)\""
|
|
BEFORE_TEXT=".*href=$QUOTED_STR.*"
|
|
AFTER_TEXT="\1"
|
|
REPLACE_EXPR="s/$BEFORE_TEXT/$AFTER_TEXT/g"
|
|
|
|
INPUT="\<a href=\"https://brandonrozek.com\" rel=\"me\"\>\</a\>"
|
|
|
|
echo "$INPUT" | sed "$REPLACE_EXPR"
|
|
``` |