Some Computer Hints


Bash String Substitution

The following string substitution operators can only be used in Bash:

${varname:position:length} Extract length characters of substring from the value of varname starting at position. 0 is the first character position.
${varname/substring/replacement} Replace first match of substring with replacement.
${varname//substring/replacement} Replace all matches of substring with replacement.
${varname/#substring/replacement} If substring matches front end of the value of varname, substitute replacement for substring.
${varname/%substring/replacement} If substring matches back end of the value of varname, substitute replacement for substring.

For the other basic string subtitution operations, see UNIX Shell.