sed function to replace any config file entry

Question

I'm trying to write a build script for SLES/RHEL that modifies config files to conform to our company standards. Some configs are formatted as setting = value and some are just setting value. I'm using sed currently and feel I'm almost there but it's not working when there is no equals sign.

Current code: (Sorry I'm not very good at formatting these properly yet...)

$ cat test.conf
setting1 value1 
setting2= value2
setting3 = value3
setting4 =value4 

Current (test) function:

#!/bin/bash
replace () {  
file=$1  
var=$2  
new_value=$3



sed -e "s/^$var=.*/$var = $new_value/" -e "s/^$var =.*/$var = $new_value/" -e "s/^$var.*/$var = $new_value/" -e "s/^$var /$var $new_value/" "$file"|grep $var  

}


replace test.conf setting1 value1new 
replace test.conf setting2 value2new  
replace test.conf setting3 value3new  
replace test.conf setting4 value4new

However I get this as a result:

$ ./functiontest
setting1 value1new= value1new 
setting2 value2new= value2new 
setting3 value3new= value3new 
setting4 value4new= value4new

It works if I take out the last sed portion, but only where there is an equals sign.

Any ideas what I'm doing wrong?

Answer 1

You can simplify the set of "similar" sed substitutions to the following:

cat replace.sh 
#!/bin/bash
replace () {
var=$2  
new_val=$3

sed -e "s/^$var *= *.*/$var = $new_val/; s/^$var [^=]*$/$var $new_val/" "$1" | grep $var 

}

replace test.conf setting1 value1new 
replace test.conf setting2 value2new  
replace test.conf setting3 value3new  
replace test.conf setting4 value4new

---

Usage:

bash replace.sh

The output:

setting1 value1new
setting2 = value2new
setting3 = value3new
setting4 = value4new

Answer 2

sed -n "s/^$var[ =].*/$var = $new_value/p" "$file"

It's sufficient to follow the variable by either space or equal sign, then one replacement fits all.

By using option -n and the p after the replacement you don't need the grep. The sed did already grep the right line.