2021-02-09 10:23:51 -0500, Chet Ramey: [...] > It's the assignment statement that's the oddball here; it's the only place > where the exit status from a command substitution has any effect. This is a > POSIX (maybe ksh) invention to provide assignment statements with a useful > exit status. [...]
It was already like that in the Bourne shell, the shell that introduced command substitution in the late 70s. Here on a PDP11 emulator running Unix V7: PDP-11 simulator V3.8-1 Disabling XQ @boot New Boot, known devices are hp ht rk rl rp tm vt : rl(0,0)rl2unix mem = 177856 # false # echo $? 1 # a=`false` # echo $? 1 -- Stephane
