Question

I have a parameter file which is a textfile – bug.par, which several parameters values listed as name of variable and its value. Just example:

par1 123 
par2 234 
par3 11 12 4 15 
par4 15
par5 18
par6 1
par7 0.05

I just want to create new files with different par5 (for exaple), say 2 additional files with par5 equal to 20, 30. Other parameters are constant.

# additional file1 with par value 20 
    par1 123 
    par2 234 
    par3 11 12 4 15 
    par4 15
    par5 20
    par6 1
    par7 0.05

# additional file1 with par value 30 
    par1 123 
    par2 234 
    par3 11 12 4 15 
    par4 15
    par5 30
    par6 1
    par7 0.05

Answer 1

To create file1:

sed 's/^ *\(par5\).*$/\1 20/' bug.par > file1

To create file2:

sed 's/^ *\(par5\).*$/\1 30/' bug.par > file2

EDIT: As per comments, running a loop:

# declare and initialize an array with 3 elements
declare -a arr=(20 30 40)

# iterate over array
for i in ${arr[@]}
do
    sed 's/^ *\(par5\).*$/\1 '$i'/' bug.par > file$i
done