php脚本上的sed bash命令

Question

I need to delete some lines from my dhcpd.conf file by a simple php script. So I'm trying to use sed command to do that. On terminal I've tryed to use this command to delete from line 1 to 3 and it works:

sed -i '1,3d' pippo.txt

The problem is that i can't understand how to use sed passing some php variable for line numers. I need something like:

sed -i '$var1,$var2d' pippo.txt

can someone help me with the correct sintax for that command on php pls. Thanks.

Answer 1

Just use double quotes to expand the variables and wrap the variables with curly braces.

var1=1
var2=2
sed -i "${var1},${var2}d" pippo.txt

You can define a variable as $var2d. If you need to use the variable $var2, followed by letter d, then you must use curly braces as in ${var2}d. However this is not necessary for $var1 in this case as there is no ambiguity, but it's good to follow as a practice.