In generating CSHENV prompts, I used stty(1) to find the width
of the current terminal, at sourcing time. SYSV and BSD use
different output formats. Presently I have tcshrc.prompt.defs
default to 80 columns when I don't know how to parse stty(1)'s
output. AIX is known to be a SYSV variant, and I've added a
case to handle this.
I didn't test the script on a virgin system, until I did it on a new
cygwin system. Now I have discovered this, and I have fixed it to properly
create the cache dir again.
