How to: remove prefix and suffix from a variable in bash

string="/scripts/log/mount_hello_kitty.log";
prefix="/scripts/log/mount_";
string=${string#$prefix}; #Remove prefix
suffix=".log";
string=${string%$suffix}; #Remove suffix
echo $string; #Prints "hello_kitty"

In the above example we have as input the variable string that contains following /scripts/log/mount_hello_kitty.log.

We want to remove from that variable the prefix, which is /scripts/log/mount_ and the suffix, which is .log.

The above code will replace in place the input that is contained in the variable string and remove the prefix and suffix we defined in the respective variables.

string=${string#$prefix} returns a copy of string after the prefix was removed from the beginning of the variable.

string=${string%$suffix} returns a copy of string after the suffix was removed from the end of the variable.