tr command in Linux can be used to trim special characters from a string in bash script. Let's say we want to remove underscore (_) from the string _hello_:

$ echo "_hello_" | tr -d "_"
 hello

As you can see the output is hello.

-d flag causes to delete _ from the whole string.

In case you want to delete multiple special characters, that's easy as pie:

$ echo "_sal-am_" | tr -d "_-"
 salam

We have removed - and _ from the string above.

Making lower case to uppercase:

tr abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ
 asdasd
 ASDASD

OR:

tr [:lower:] [:upper:]
 asdasd
 ASDASD

Turn {} into ():

$ echo '{hello}' | tr '{}' '()'
 (hello)

#linux #tr #translate #trim #bash #sysadmin