### 3.3 Comments in `m4` input ¶

Comments in `m4` are normally delimited by the characters ‘`#`’ and newline. All characters between the comment delimiters are ignored, but the entire comment (including the delimiters) is passed through to the output—comments are not discarded by `m4`.

Comments cannot be nested, so the first newline after a ‘`#`’ ends the comment. The commenting effect of the begin-comment string can be inhibited by quoting it.

    $ m4
    `quoted text' # `commented text'
    ⇒quoted text # `commented text'
    `quoting inhibits' `#' `comments'
    ⇒quoting inhibits # comments

The comment delimiters can be changed to any string at any time, using the builtin macro `changecom`. See Changing the comment delimiters, for more information.