11.2.1 The Queue Identifier
To ensure that new filenames are not the same as the names of files that might
already be in the queue, sendmail uses the following pattern for each new ident:
AApid ?†? prior to V8.6
hourAApid ?†? beginning with V8.6
YMDhmsSEQpid ?†? beginning with V8.10
Here, pid is the process identification number of the incarnation of sendmail that is
trying to create the file. Because sendmail often fork(2)s to create queue entries, that
pid is likely to be unique, resulting in a unique ident. Th eAA is used as a clock to
prevent duplicate filenames. For V8.6 through V8.9 sendmail, an extra letter prefixes
the AA. Shown as hour, it is an uppercase letter that corresponds to the hour (in a
Table 11-1. Queue file types
File ?§ Description
df ?§11.2.2 on page 398 Data (message body)
lf ?§11.2.3 on page 398 Lock file (obsolete and removed as of V5.62)
nf ?§11.2.4 on page 399 ID creation file (obsolete and removed as of V5.62)
tf ?§11.2.6 on page 400 Temporary qf rewrite image
xf ?§11.2.7 on page 401 Transcript file
qf ?§11.2.5 on page 399 Queue control file (and headers)
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11.2 Parts of a Queued Message | 397
24-hour clock) that the identifier was created. For example, a file created in hour
three of the day will have a D prefixed (the hour begins at midnight with A).
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