Help needed sed command.

Shell Programming and Scripting
1

I want to execute below command using line number as a variable.

sed '5c\ disk = jskdjfdsk' vm.cfg

How do i substitute a variable in place of 5
for example
i tried substituting

sed '$variablec\ disk = jskdjfdsk' vm.cfg
and 
sed '"$variable"c\ disk = jskdjfdsk' vm.cfg)

but they didnt worked .
Please help

2

Double quote your sed and use the variable as ${variable}

i.e.

sed "${variable}c\ disk = jskdjfdsk" vm.cfg

Or put a space after it:

sed "$variable c\ disk = jskdjfdsk" vm.cfg

to separate it from the character c

3

Drop the single quotes and bring in double quotes. Single quotes prevent variable expansion.

Try if this works

sed "${variable}c\ disk = jskdjfdsk" vm.cfg