Bash：在设置“set -e”时捕获退出代码而不是中止？

Question

在大多数情况下，我更喜欢我的脚本在遇到意外错误时终止，因此通常以set -e -u -E -o pipefail启动它们。

但是，有时我需要捕获单个调用的退出代码而不是终止。 这导致像这样的结构

# (1) Verbose. Breaks when moved between scripts 
#              with different global -e setting.
set +e
COMMAND WITH A LOT OF ARGUMENTS \
    | AND MAYBE EVEN PIPES \
    | MAYBE OVER MANY LINES
exitCode=$?
set -e

# (2) Verbose.
if COMMAND WITH A LOT OF ARGUMENTS \
    | AND MAYBE EVEN PIPES \
    | MAYBE OVER MANY LINES
then exitCode=$?
else exitCode=$?
fi

# (3)
exitCode=0
COMMAND WITH A LOT OF ARGUMENTS \
    | AND MAYBE EVEN PIPES \
    | MAYBE OVER MANY LINES \
    || exitCode=$?

# (4) Brittle, must not mix up order of && and ||
COMMAND WITH A LOT OF ARGUMENTS \
    | AND MAYBE EVEN PIPES \
    | MAYBE OVER MANY LINES \
     && exitCode=$? || exitCode=$?

# (5), doesn't work with `set -o pipefail`
COMMAND WITH A LOT OF ARGUMENTS \
    | AND MAYBE EVEN PIPES \
    | MAYBE OVER MANY LINES | cat
exitCode=$PIPESTATUS

# (6) Requires maintaining a function across scripts.
captureExitCode COMMAND WITH A LOT OF ARGUMENTS \
    | AND MAYBE EVEN PIPES \
    | MAYBE OVER MANY LINES
# where
captureExitCode() {
    # any of the above constructs with "$@" as command
}

所有这些要么冗长，要么在视觉上有些难以解析，特别是如果COMMAND ...是一个多行管道命令。 至少，他们没有很好地传达他们的意图。 在captureExitCode的情况下，该函数必须跨脚本复制。

是否有一些不那么冗长的内置习语来捕获退出代码？

Answer 1

在子 shell 中运行有问题的命令并禁用errexit ：

(
  set +e
  run buggy code failing without proper error handling
)
exitcode=$?

例子：

#! /bin/bash

set -e

if ( set +e
     false
   )
then
  echo success
else
  echo failure
fi

顺便说一句：当你这样写管道时，你不需要反引号：

echo abc |
  tr a x |
  sed 's/^x/y/'