Variable modifiers in csh and bash: bash

Bash do not have variable modifiers, but it has a feature called Posix, which originates from ksh and seems to be more powerful, albeit somewhat more cryptic.

% is used to remove smallest suffix pattern. Like:

$ gatesfile=/home/gates/bin/foo.bar
$ echo ${gatesfile%.bar}
/home/gates/bin/foo

Of course you can append something to the end and forge the functionality of replace:

$ echo ${gatesfile%.bar}.x
/home/gates/bin/foo.x

%% is to remove largest suffix pattern:

$ gatesfile=posix/src/std
$ echo ${gatesfile%%/*}
posix

# is used to remove smallest prefix pattern, and ## is to remove largest prefix pattern

In summary, given:

a=/a/b/c/d
b=b.xxx

  +------------------------------------+
  |csh    bash           result        |
  +------------------------------------+
  |$a:h   ${a%/*}        /a/b/c        |
  |$a:t   ${a##*/}       d             |
  |$b:r   ${b%.*}        b             |
  |$b:e   ${b##*.}       xxx           |
  +------------------------------------+