1INCLAN: echo - variable to control the echoing of commands

"echo" is a variable that determines which commands are echoed, i.e. copied
to standard output before execution. The possible settings are:

off     Commands are not echoed.
NULL    (or not set at all) In macros, all commands except those built into 
        the command line interpreter are echoed; interactive commands are 
        not echoed.
on      Commands that are not built into the command interpreter are 
        echoed regardless of whether they occur in macros or interactively.
large   Same as "on", except that the echo is surrounded by blank lines.
full    All commands are echoed, and the corresponding line numbers in
        macros are given.

Labels are not included in the echo, but variable substitutions are.
Statements preceded by "@" are only echoed if echo has the value "full".