UNIX for Dummies Questions & Answers

     ${parameter%word}
           Remove Smallest  Suffix  Pattern.  The  word  will  be
           expanded to produce a pattern. The parameter expansion
           then will result in parameter, with the smallest  por-
           tion of the suffix matched by the pattern deleted.

     ${parameter%%word}
           Remove  Largest  Suffix  Pattern.  The  word  will  be
           expanded to produce a pattern. The parameter expansion
           then will result in parameter, with the  largest  por-
           tion of the suffix matched by the pattern deleted.

     ${parameter#word}
           Remove Smallest  Prefix  Pattern.  The  word  will  be
           expanded to produce a pattern. The parameter expansion
           then will result in parameter, with the smallest  por-
           tion of the prefix matched by the pattern deleted.

     ${parameter##word}
           Remove  Largest  Prefix  Pattern.  The  word  will  be
           expanded to produce a pattern. The parameter expansion
           then will result in parameter, with the  largest  por-
           tion of the prefix matched by the pattern deleted.

     ${parameter%word}

     x=file.c
     echo ${x%.c}.o
     file.o

     ${parameter%%word}

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

     ${parameter#word}

     x=$HOME/src/cmd
     echo ${x#$HOME}
     /src/cmd

     ${parameter##word}

     x=/one/two/three
     echo ${x##*/}
     three

$ var1='123456789123456789'
$ var2=${var1#??????????}
$ echo $var2
23456789