When $ZCOMPILE is null, GT.M uses the default M command qualifiers -IGNORE, -LABEL=LOWER, -NOLIST, and -OBJECT. See ChapterA 3: a??Development Cyclea?? for detailed descriptions of the M command qualifiers.
Example:
$ export gtmcompile="-LIST -LENGTH=56 -SPACE=2" $ gtm GTM>WRITE $ZCOMPILE -LIST -LENGTH=56 -SPACE=2 GTM>SET $ZCOMPILE="-LIST -NOIGNORE" GTM>WRITE $ZCOMPILE -LIST -NOIGNORE GTM>ZLINK "A.m" GTM>HALT $ echo $gtmcompile -LIST -LENGTH=56 -SPACE=2
This example uses the environment variable gtmcompile to set up $ZCOMPILE. Then it modifies $ZCOMPILE with the SET command. The ZLINK argument specifies a file with a .m extension (type), which forces a compile. The compile produces a listing for routine A.m and does not produce an object module if A.m contains compilation errors. After GT.M terminates, the shell command echo $gtmcompile demonstrates that the SET command did not change the environment variable.