使用带有sed的bash脚本修改文件

Question

similar to these questions:

• modify config file using bash script
• How do I use sed to change my configuration files, with flexible keys and values?

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 ?

Answer 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}
'

Answer 2

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.

Answer 3

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');