grep a pattern and replace a value in it and write to the same file.

Shell Programming and Scripting
1

I have some complication with this, I have a file like below[db.sh] for DEV_1 till DEV_10. and the db values are set accordinly which are not unique. For example DEV1,DEV4,DEV6 can have the same target DB name.
I waned to identify[grep] for DEV_2 and then replace the TARGET_DATABASE value with the new DB name, can you suggest.

DEV_1_SOURCE_DATABASE=server1
DEV_1_SOURCE_AUDIT_DATABASE= server1
DEV_1_TARGET_DATABASE=server4
DEV_1_TARGET_AUDIT_DATABASE=server4

DEV_2_SOURCE_DATABASE=server2
DEV_2_SOURCE_AUDIT_DATABASE= server2
DEV_2_TARGET_DATABASE=server5
DEV_2_TARGET_AUDIT_DATABASE=server5
.
.
.
.
.
.

i used sed like sed 's/`cat db.sh | grep -i DEV_2 | grep -i database | egrep -v "audit|source"`/newdbname' < db.sh > db.sh_new
i got a error;
tried awk but dint work as i am trying to pass command on:
can someone help in this :
my ultimate need is i need to grep a pattern and replace the value in that location only,

this might be too long !!!!

2

can you post the required output?

3

In case new db name is "UNIX",
Are you expecting the output as follows?

DEV_1_SOURCE_DATABASE=server1
DEV_1_SOURCE_AUDIT_DATABASE= server1
DEV_1_TARGET_DATABASE=server4
DEV_1_TARGET_AUDIT_DATABASE=server4

DEV_2_SOURCE_DATABASE=server2
DEV_2_SOURCE_AUDIT_DATABASE= server2
DEV_2_TARGET_DATABASE=UNIX
DEV_2_TARGET_AUDIT_DATABASE=server5

Is this what your expecting?

4

yes, u are right,, i expect the outut as above,,

but i would like to rremind that the original file contains "server4" as a value for more than one DB target,, i mean not only DEV_2 target is server4 but also say DEV_3 will be targetted to server4.

5

This may help you.

sed 's/\(DEV_2_TARGET_DATABASE=\)\(.*\)/\1UNIX/g' t1
6

ope the file in vi editor

1.hit esc .
2. Type %s/"pattern to be matched"/"pattern to be replaced"/g

This will replace all the instances of pattern to be matched

7

since i could not get your expectation clearly,
Here am giving some solution

$cat file

DEV_1_SOURCE_DATABASE=server1
DEV_1_SOURCE_AUDIT_DATABASE= server1
DEV_1_TARGET_DATABASE=server4
DEV_1_TARGET_AUDIT_DATABASE=server4

DEV_2_SOURCE_DATABASE=server2
DEV_2_SOURCE_AUDIT_DATABASE= server2
DEV_2_TARGET_DATABASE=server5
DEV_2_TARGET_AUDIT_DATABASE=server5

Solution 1:

script1.sh
a=` cat file | grep -w "DEV_2_TARGET_DATABASE" | cut -d '=' -f 2`
sed "s/\($a\)/newdb/g" file > file1
mv file1 file

The above script will take the value assigned for DEV_2_TARGET_DATABASE, and substitute that value i.e "server5" to newdb in the whole file content. ( even for DEV 4 or DEV 3)

Solution 2:

If you want to substitute only DEV_2_TARGET_DATABASE=server5 to DEV_2_TARGET_DATABASE=newdb

sed "s/\(DEV_2_TARGET_DATABASE=\)\(.*\)/\1newdb/g" file

Hope this helps..