如何从 Bash 中的返回码中提取位

Question

我正在使用返回此错误代码的 pylint 实用程序：

Pylint should leave with following status code:

* 0 if everything went fine
* 1 if a fatal message was issued
* 2 if an error message was issued
* 4 if a warning message was issued
* 8 if a refactor message was issued
* 16 if a convention message was issued
* 32 on usage error

status 1 to 16 will be bit-ORed so you can know which different
categories has been issued by analysing pylint output status code

现在我需要确定 Bash 中是否出现致命或错误消息。怎么做呢？我想我需要位操作；-)

编辑：我知道我需要按位和数字三 (3) 进行操作，并针对 null 进行测试，以查看是否发出了致命消息或错误消息。我的问题很简单：使用 bash 语法来实现。输入是 $?，输出又是 $? （例如使用测试程序）。谢谢！

Answer 1

当且仅当状态为奇数且最低有效数字为 1 时，将发出致命消息。

当且仅当状态的下一个最高有效数字为 1 时，将发出错误消息。

所以你想检查最后两位是否都是1；换句话说，检查 0b11 状态代码的按位 and 是否为 3。

Answer 2

要将类似的内容嵌入到设置了 errexit 的脚本中，您可以使用如下形式：

#!/bin/bash
set -o errexit
set -o nounset
(
    rc=0;
    pylint args args || rc=$?;
    exit $(( $rc & 35 )) # fatal=1 | error=2 | usage error=32
)

灵感来自 David 的评论 和 这个答案

你可以通过用 python -c 替换 pylint blah blah 来查看它退出（4+8+16）”

Answer 3

bash 中最后执行的命令的返回码可用作 $?。

[/tmp] % touch bar
[/tmp] % ls /tmp/bar 
/tmp/bar
[/tmp] % echo $?
0
[/tmp] % ls /tmp/baaz
ls: /tmp/baaz: No such file or directory
[/tmp] % echo $?
1
[/tmp] % 

如果您要从 python 的 subprocess 模块调用外部命令，一旦子进程退出，您就可以从 Popen 对象获取外部命令的返回码。

Answer 4

使用（可能不是最佳的）bash 算术内容：

for status in 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
do
    if [ $status = 0 ]
    then echo $status: it worked perfectly
    elsif [ $(( $status & 3 )) != 0 ]
    then echo $status: a fatal or error message was sent
    else echo $status: it sort of worked mostly
    fi
done

输出：

0: it worked perfectly
1: a fatal or error message was sent
2: a fatal or error message was sent
3: a fatal or error message was sent
4: it sort of worked mostly
5: a fatal or error message was sent
6: a fatal or error message was sent
7: a fatal or error message was sent
8: it sort of worked mostly
9: a fatal or error message was sent
10: a fatal or error message was sent
11: a fatal or error message was sent
12: it sort of worked mostly
13: a fatal or error message was sent
14: a fatal or error message was sent
15: a fatal or error message was sent
16: it sort of worked mostly

我强烈怀疑脚本（测试）可以变得更紧凑或更清晰（特别是在 elif 子句中），但这似乎有效（我需要去工作）。

pylint ...
status=$?     # Catch exit status before it changes
if [ $status = 0 ]
then echo $status: it worked perfectly
elsif [ $(( $status & 3 )) != 0 ]
then echo $status: a fatal or error message was sent
else echo $status: it sort of worked mostly
fi

Answer 5

在 Bash 中你可以使用双括号：

#fatal error
errorcode=7
(( res = errorcode & 3 ))
[[ $res != 0 ]] && echo "Fatal Error"

Answer 6

知道了！

[ $(($NUMBER & 3)) -ne 0 ] && echo Fatal error or error was issued

谢谢！

Answer 7

Bash 支持按位运算符...

$ let "x = 5>>1"
$ echo $x
2
$ let "x = 5 & 4"
$ echo $x
4