[GRASS-user] grass-7.9.svn: cannot read input data file from shell script

[Rich Shepard]

Running grass-7.9.svn on Slackware-14.2/x86_64.

The command line is:
v.in.ascii in=$HOME/projects/<state>/<project>/data/features/points.dat
out=points for=point col='x double precision, y double precision, name
char(10)' x=1 y=2 --o (Some names redacted.)

Trying to run v.in.ascii in the grass shell results in this:
ERROR: Unable to open input file
        </home/rshepard/projects/<state>/<proj_name>/data/features/points.dat>

Permissions on the input ASCII text file are 644.

What might cause grass to fail to read a file that's world readable?

TIA,

Rich