exit(-1)或者return(-1)shell得到的退出码为什么是255

Catchall for general errors let “var1 = 1/0″ Miscellaneous errors, such as ”divide by zero” and other impermissible operations 2 Misuse of shell builtins (according to Bash documentation) empty_function() {} Seldom seen, usually defaults to exit code 1 126 Command invoked cannot execute   Permission problem or command is not an executable 127