Kleine Denksportaufgabe für den Morgen:

Was gibt folgendes Skript aus, d.h. was wird durch das set -e als Fehler gewertet und führt zum Abbruch des Skripts:

#!/bin/sh
set -e
! false ; echo 0
! true ; echo 1
true && true ; echo 2
true || true ; echo 3
false && true ; echo 4
false || true ; echo 5
false && false ; echo 6
true || false ; echo 7
true && false ; echo 8
false || false ; echo 9

f () { false; echo 10; }
if f; then echo 11; else echo 12; fi

Hinweise aus man 1 bash:

-e

Exit immediately if a simple command (see SHELL GRAMMAR above) exits with a non-zero status.

The shell does not exit if the command that fails is part of the command list immediately following a while or until keyword, part of the test in an if statement, part of a && or ⎪⎪ list, or if the command’s return value is being inverted via !.

Simple Commands

A simple command is a sequence of optional variable assignments followed by blank-separated words and re-directions, and terminated by a control operator.

Control operator

A token that performs a control function.

It is one of the following symbols:

|| & && ; ;; ( ) | <newline>

…

The control operators && and ⎪⎪ denote AND lists and OR lists, respectively.

An AND list has the form :

command1 && command2 :

command2 is executed if, and only if, command1 returns an exit status of zero. :

An OR list has the form :

command1 ⎪⎪ command2 :

command2 is executed if and only if command1 returns a non-zero exit status.

The return status of AND and OR lists is the exit status of the last command executed in the list.

man 1 sh drückt es etwas präziser aus:

-e errexit

If not interactive, exit immediately if any untested command fails.

The exit status of a command is considered to be explicitly tested if the command is used to control an if, elif, while, or until; or if the command is the left hand operand of an && or || operator.