又一个 ksh 的 bug

Nov, 9, 2009, by mattw

见鬼的事怎么总是我碰上。

$ cat kshbug
{ return 0; } &
evil=$(/bin/true)   # XXX: works fine without this line
wait $!
echo $?

$ ksh kshbug
127

$ ksh --version
  version         sh (AT&T Labs Research) 1993-12-28 r

The correct return code should be 0. Without the line of "eval=$(bin/true)" everything works fine. The problem happens only when

  1. Execute a function or a clause in background, and
  2. A subshell is invoked between the background execution and the "wait", and
  3. An external command is executed in the subshell

I googled for a while, there's no ksh bug report so far, workaround could be use output text for return code check instead. Note there's a similar report for ksh on solaris but it's not the identical issue.

Pdksh (public domain ksh) doesn't have the problem. (See another bug.)

Update: this issue doesn't happen on Ubuntu ksh version "sh (AT&T Research) 93s+ 2008-01-31".