[Chapter 27] 27.2 Comments
Author: Bryan Costales & Eric Allman
Date: 1999-01-06T19:49:49Z

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| Chapter 27 The Configuration File |

## 27.2 Comments

Comments provide you with the documentation necessary to maintain the configuration file. Because comments slow sendmail down by only a small amount, it is better to overcomment than to undercomment.

Blank lines and lines that begin with a `#` character are considered comments and are ignored. A blank line is one that contains no characters at all (except for its terminating newline). Indentation characters (spaces and tabs) are invisible and can turn an apparently blank line into an empty-looking line, which is not ignored:

>     # text a comment
>     tabtext a continuation line
>      a blank line
>     tab an "empty-looking line"

Except for V8 sendmail and two special cases, comments occupy the entire line. The two special cases are the `R` and `S` configuration commands. The `R` command is composed of three tab-separated fields, the third field being a comment that does not require a leading `#` character:

>     Rlhs      rhs       comment

The pre-V8.7 `S` command looks only for a number following it and ignores everything else, so it may also be followed by a comment:

>     S3 this is a comment

No other commands allow comments to follow on the same line:

>     CWlocalhost mailhost  # This won't work prior to V8

27.1 Overall Syntax |  | 27.3 V8 Comments