sed replace text - escape characters

Question

I have a mysqldump file in which I want to replace the following text <a href="/tag/ with <a href="http://www.mydomain.com/tag/ but can't find a way to correctly escape all special characters.

I'm using the following command (+ a few other variants)
cat wordpress_posts.sql | sed 's%/<a href="\/\tag\/\/<a href="\http:/\/\www.mydomain.com/\tag/\/%g' > wordpress_posts_new.sql
but it's not working.

Can anybody help?

Update 1: Turns out that the source string in the mysqldump isn't <a href="/tag/ but <a href=\"/tag/ (note the extra backslash after the equal symbol)
Here's a pastebin of one line of the SQL file which contains the string I want to replace: http://pastebin.com/8G5mcxpJ

I tried all 3 suggested versions of the sed command, but none would replace the above string with <a href=\"http://www.mydomain.com/tag/ (yes I added the backslash after the equal symbol)

All of the answers below work with the data as specified in your question. In your real data there is an additional `\\` that needs to be dealt with. GIGO ! — user9517, Aug 19 '12 at 12:30
It doesn't matter really - non of the answers have been updated since, they all work with your original data. — user9517, Aug 19 '12 at 12:35
quanta answered 19 minutes ago with a working answer based on my updated question, which worked. Thus I accepted his answer. — George Tasioulis, Aug 19 '12 at 12:41

scai · Answer 1 · 2012-08-19T13:31:04.630

6

You don't have to escape /, you can just use any other delimiter:

sed 's#<a href=\\"/tag/#<a href="http://www.mydomain.com/tag/#' wordpress_posts.sql

edited Aug 19 '12 at 13:31

answered Aug 19 '12 at 08:29

scai

2,199
1
12
16

I hoped that this would work but it didn't :( original and new file have the same size, plus with a grep I can still see instances of ` – George Tasioulis Aug 19 '12 at 08:58
1

If this pattern occurs several times per line, you have to add a `g` at the end, like `sed '#foo#bar#g' myFile` – scai Aug 19 '12 at 09:22
Tried that too, but no. I updated the post with a link to a pastebin containing one line of the sql dump which contains the string I want to replace. – George Tasioulis Aug 19 '12 at 11:43
The backslash at `href=\"/tag/` was missing, I updated my answer. – scai Aug 19 '12 at 13:31
1

People should really use other delimiters, as you've pointed out. "Picket fences" cause confusion and more often lead to syntax error. – tacotuesday Aug 19 '12 at 18:35

quanta · Accepted Answer · 2012-08-19T08:27:42.590

4

No need to pipe cat to sed:

$ sed 's/<a href="\/tag\//<a href="http:\/\/www.mydomain.com\/tag\//g' wordpress_posts.sql

Remove the percentage sign
You only need to escape the slash
Specify an in-place editing (-i) if you want

edited Aug 19 '12 at 08:27

answered Aug 19 '12 at 08:20

quanta

50,327
19
152
213

1

This gives me an `sed: -e expression #1, char 3: unterminated `s' command` error. – George Tasioulis Aug 19 '12 at 08:56
Are you sure you specify enough 3 delimiters `'s/pattern/replacement/g'`? – quanta Aug 19 '12 at 09:32
Well I simply copy-pasted your command and changed www.mydomain.com to my own domain, so I suppose it should have worked. I updated my initial post and have added a pastebin link with a line of the sql file containing the string I want to replace. – George Tasioulis Aug 19 '12 at 11:45
Escape the additional backslash with a backslash `sed 's/ – quanta Aug 19 '12 at 12:16
Yeap now it worked :) – George Tasioulis Aug 19 '12 at 12:26

score 3 · Answer 3 · answered Aug 19 '12 at 08:30

3

$ cat wordpress_posts.sql | sed 's/\/tag\//http:\/\/www.mydomain.com\/tag\//' > wordpress_posts.sql

answered Aug 19 '12 at 08:30

Chida

2,471
1
16
29

Tried that too, but it didn't work :( I've added a link to a pastebin with the string I want to find and replace to my initial post (Update 1). Maybe this will help.. – George Tasioulis Aug 19 '12 at 11:45

sed replace text - escape characters

3 Answers3