When is STTY ignored?

[Stephane Chazelas <stephane.chazelas@gmail.com>]

Hello,

It's not very clear to me when one may use STTY.

STTY=-echo line
zsh -c 'STTY=-echo line'
STTY=-echo command line
f() line; STTY=-echo f
f() STTY=-echo line; f

work (at reading a line with tty echo disabled)

But:

STTY=-echo read line
STTY=-echo eval line
zsh -c 'f() line; STTY=-echo f'
zsh -c 'f() STTY=-echo line; f'

don't (stty not run).

See also:

$ f() STTY=-onlcr line; STTY=-echo f; stty
asd
   asd
      speed 38400 baud; line = 0;
                                 -brkint -imaxbel iutf8
                                                       -onlcr

-echo not applied, -onlcr not restored.

-- 
Stephane