sendmail, 4th Edition

Processing the Command Line

The sendmail program’s ability to perform different tasks necessitates that the command line be processed in steps:

First

The command line is prescanned to set its -d debugging switch. That switch allows you to watch all the steps taken by sendmail prior to processing the rest of the command-line switches.

Second

Internal sendmail macros are given their starting values, and then the command line’s argv[0] (the name used to run sendmail) is processed. That name can determine the sendmail program’s mode of operation.

Third

The command-line switches are processed. Although the configuration file is read after the command line is processed, options in the command line (with -o and -O) still supersede those in the configuration file.

Fourth

The configuration file is read.

Fifth

If sendmail is running in a mode that allows it to verify or deliver to recipients, the remainder of the command line is processed to extract the recipient list.