commandliners

Start with a string:

$ a="hi, this is my beautifull string"

Positional substrings:

1. Substring from the 4th character on:

   $ echo ${a:3}
   this is my beautifull string
   

2. Substring of length 4 from the 10th character:

   $ echo ${a:9:4}
   is m
   

Substring modification:

1. Substitute the first instance of a substring:

   $ echo ${a/full/ful}
   hi, this is my beautiful string
   

2. Same example:

   $ echo ${a/h/H}
   Hi, this is my beautifull string
   

3. Substitute all the instances of a substring:

   $ echo ${a//hi/HI}
   HI, tHIs is my beautifull string
   

Substring removal:

1. Remove the shortest match of a substring from the start:

   $ echo ${a#h*i}
   , this is my beautifull string
   

2. Same, starting at the end

   $ echo ${a%i*g}
   hi, this is my beautifull str
   

3. Remove the longest match of a substring from the start:

   $ echo ${a##h*i}
   ng
   

4. Same, starting at the end

   $ echo ${a%%i*g}
   h
   

These are for bash-2, they probably work on bash-3 and they seem to work on ksh (under OS X at least).