modify a file using a bash script with sed

Question

similar to these questions:

In a file like this:

define('_DB_NAME_', 'anything');
define('_DB_USER_', 'something else');
define('_DB_PASSWD_', 'and another value');

how to use sed to replace the value anything, something and another (which are unknown) by refering to the key values _DB_NAME_, _DB_USER_ and _DB_PASSWD?

Do you want to replace the second argument of the first line, or do you want to replace the `'anything'` argument wherever it appears? — Beta, Nov 14 '16 at 02:25
I want to replace the value `anything` (which is unknown) depending on the key `_DB_NAME_` — François Romain, Nov 14 '16 at 02:28

score 1 · Answer 1 · answered Nov 14 '16 at 02:35

1

You probably want:

sed -E "
  s/('_DB_NAME_', ')[^']+/\1ABC/
  s/('_DB_USER_', ')[^']+/\1DEF/
  s/('_DB_PASSWD_', ')[^']+/\1GHI/
"

I think awk is more readable:

awk -F "'" -v OFS="'" '
    $2 == "_DB_NAME_"   {$4 = "ABC"}
    $2 == "_DB_USER_"   {$4 = "DEF"}
    $2 == "_DB_PASSWD_" {$4 = "GHI"}
    {print}
'

answered Nov 14 '16 at 02:35

glenn jackman

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the first one with sed says: `\1 not defined in the RE` – François Romain Nov 14 '16 at 02:40
Try using `-r` instead of `-E` . What OS are you using? – glenn jackman Nov 14 '16 at 02:42
now it's on macos, but eventually it will run on linux (I don't know exactly, it's a shared hosting running apache) – François Romain Nov 14 '16 at 02:50

Beta · Accepted Answer · 2016-11-14T02:42:42.153

1

sed "s/\(define('_DB_NAME_', \).*/\1'new value');/" filename

and likewise for the other two.

If you want to alter the file in place, you can use -i, but you have to be careful, different versions of sed handle that differently.

edited Nov 14 '16 at 02:42

answered Nov 14 '16 at 02:35

Beta

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score 0 · Answer 3 · answered Nov 14 '16 at 02:26

0

sed -i -e 's/anything/newanything/g;s/something/newthing/g;s/another/newanother/' tempfile

Where tempfile contains that code you had. Output looks like this

define('_DB_NAME_', 'newanything');
define('_DB_USER_', 'newthing else');
define('_DB_PASSWD_', 'and newanother value');

answered Nov 14 '16 at 02:26

davidejones

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I edited my question for clarity. The value `anything` is unknown. So the goal is to replace it by referring to `_DB_NAME_` – François Romain Nov 14 '16 at 02:34
@francoisromain ah i see sorry I jumped the gun a little there – davidejones Nov 14 '16 at 02:35

modify a file using a bash script with sed

3 Answers3