Node:Change files, Previous:Output files, Up:Files
The primary input to the FWEB processors is the test.web
source file. However, a change file test.ch
can also be
specified. A change file consists of instances of the following
structure:
@x (One or more lines of text, EXACTLY as in the web file. Copy these lines with an editor; don't type them from scratch.) @y (Replacement text.) @z
The change-file mechanism allows one to insert local changes or test new code without physically modifying the original web file.
To specify a change file, use its name as the second file name on the
command line. The extension .ch
is assumed by default. For
example,
ftangle test test
processes test.web
with the change file test.ch
.
In addition to @x
, @y
, and @z
, the only
@
commands allowed in a change file are language-changing
commands such as @c
and the special commands @[
and
@]
. The command @[
is used for column-oriented
languages such as FORTRAN-77 and means switch into code
mode. Similarly, @]
means switch out of code mode.
All @
commands in a change file must begin in column 1. Lines
not beginning with @
are ignored, so may be used as comments.
Comments may also be included on the @x
, @y
, and/or
@z
lines.