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37. Debugging with -d

Contents:
The Syntax of -d
Debugging Behavior
Interpreting the Output
Pitfalls
Reference in Numerical Order

The sendmail program offers a command-line switch for investigating and solving mail problems. The debugging -d switch allows you to observe sendmail's inner workings in detail.

37.1 The Syntax of -d

The form for the -d command-line switch is

-dcategory.level,category.level,....
-dANSI                                         <- V8.8 and above

The -d may appear alone, or it may be followed by one or more category.level pairs separated by commas or, beginning with V8.8, by the word ANSI. We cover the category.level pairs first then ANSI.

The category limits debugging to an aspect of sendmail (such as queuing or aliasing). The level limits the verbosity of sendmail (with low levels producing the least output).

The category is either a positive integer or a range of integer values specified as

first-last

When category is a range, first is a positive integer that specifies the first category in the range. It is followed by a hyphen character (-) and then last, a positive integer that specifies the last category in the range. The value of first must be less than the value of last, or the range will be ignored.

The level is a positive integer. A level of 0 causes sendmail to produce no output for the category.

When the -d is specified with neither category nor level, an internal sendmail default is used:

0-99.1

This default causes sendmail to set all the categories, from zero through 99 inclusive, to a level of 1.

When category is included but level is omitted, the value for level defaults to 1. When a dot (.) and level are included, but category is omitted, the value for category defaults to 0.

The maximum value that may be specified for a single category is 99. Any value specified above the maximum is reduced to the maximum. The maximum value for level is that of an unsigned char (255 decimal). Nondigits for the category or range evaluate to zero. Nondigits for the level evaluate to 1.

The level specifies the maximum amount of verbose output to produce. All levels below the level specified also produce output.

The expression that produces the maximum debugging output is

-d0-99.127

But beware that debugging levels of 100 or greater may cause sendmail to modify its behavior. (For example, one category at such a high level causes sendmail to not remove its temporary files.) For this reason, -d0-99.99 is the maximum level recommended.

Debugging can be turned on from the command line and from within -bt rule-testing mode (see Section 38.7, "Add Debugging for Detail"). If sendmail is wrongly compiled with SMTPDEBUG defined (see Section 18.8.42, SMTPDEBUG), debugging can be turned on via an SMTP DEBUG command.

Beginning with V8.8 sendmail, a special debugging word can be specified at the command line to cause debugging output to become clearer:

-dANSI        <- V8.8 and above

ANSI is case sensitive and must be the only argument following the -d. If you wish to combine it with other debugging switches, you must specify them separately:

-dANSI -d0.4

ANSI causes defined macros, class macros, and operators to be displayed in reverse video:

R $+        $#local $:  $1

This is truly a "hack." The escape code to highlight characters is hard-coded into sendmail. Your display must support ANSI standard escape sequences for this to work. There is no plan to use standard library support for this "aid to rule-set hackers."


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