Perhaps sed was not meant to be a programming language, but does have a limited
form of flow control. Adding to sed some features common in other languages will
facilitate solving some problems and perhaps make sed more readable. Here are
features I want to see in an improved sed.
-
global macros - sed supports macros within a regular expression and within a
substitute command. These are \1 through \9 and are defined by previously placed
pairs of escaped parentheses. A formal global macro definition will reduce the size and increase the readability of large sed scripts.
-
global integer variables will facilitate counting and enumeration of replacements
within the actual substitution.
-
a way to compare the "hold" and "pattern" spaces and then "branch" equal and not equal
-
the ability to branch on substitution or on no substitution for the substitute
command
-
the ability to branch on match or branch on no match for an "address" (which may
be a regular expression.) This command immediately follows a pair of
braces.
