Linux 带双管道的bash集-e函数

有人能解释一下这种行为吗？我觉得很奇怪

#!/bin/bash

set -e

_func() { 
  cat non-existant-file
  return 0
}

_func || echo "Not seen since _func returned zero"
_func
echo "Not seen since _func returned non-zero"

输出（GNU bash，版本4.3.42（1）-发行版（x86_64-pc-linux-GNU））：

---

如果您查看bash的手册页，它会特别提到：

特别是

如果失败的命令是在&&或| |列表中执行的[…]任何命令的一部分，则shell不会退出，除了最后的&&或| |[…]之后的命令。

这种行为完全符合记录/预期

如果您运行这样的操作，您可以亲自看到这一点：

#!/bin/bash

set -ex
# set -x will tell you exactly where the shell exits.

_func() { 
  cat non-existant-file
  return 0
}

#_func || echo "Not seen since _func returned zero"
cat non-existant-file || _func
_func
echo "Not seen since _func returned non-zero"

---

从手册页：

    set   -e      Exit immediately if a pipeline (which may consist  of  a
                  single  simple  command),  a list, or a compound command
                  (see SHELL GRAMMAR above),  exits with a  non-zero  sta‐
                  tus.   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 following the
                  if or elif reserved words, part of any command  executed
                  in  a  &&  or  ||  list except the command following the
                  final && or ||, any command in a pipeline but the  last,
                  or  if the command's return value is being inverted with
                  !.  If a compound command other than a subshell  returns
                  a  non-zero status because a command failed while -e was
                  being ignored, the shell does not exit.  A trap on  ERR,
                  if set, is executed before the shell exits.  This option
                  applies to the shell environment and each subshell envi‐
                  ronment  separately  (see  COMMAND EXECUTION ENVIRONMENT
                  above), and may cause subshells to exit before executing
                  all the commands in the subshell.

这正是你这里的情况

    set   -e      Exit immediately if a pipeline (which may consist  of  a
                  single  simple  command),  a list, or a compound command
                  (see SHELL GRAMMAR above),  exits with a  non-zero  sta‐
                  tus.   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 following the
                  if or elif reserved words, part of any command  executed
                  in  a  &&  or  ||  list except the command following the
                  final && or ||, any command in a pipeline but the  last,
                  or  if the command's return value is being inverted with
                  !.  If a compound command other than a subshell  returns
                  a  non-zero status because a command failed while -e was
                  being ignored, the shell does not exit.  A trap on  ERR,
                  if set, is executed before the shell exits.  This option
                  applies to the shell environment and each subshell envi‐
                  ronment  separately  (see  COMMAND EXECUTION ENVIRONMENT
                  above), and may cause subshells to exit before executing
                  all the commands in the subshell.