在哪里可以找到 SUDO_COMMAND 环境变量？

Question

我目前正在使用 Ubuntu 学习 Linux 的基础，并且有一些活动需要查找有关环境变量的信息。我已经找到了 6/7 的信息，但就是找不到SUDO_COMMAND。名单是这样的：

SHELL=/bin/bash
USER=student
SUDO_COMMAND=
PWD=/home
HOME=/home/student
LOGNAME=student
OLDPWD=/home/student 

我注意到信息是按顺序排列的，并且SUDO_COMMAND在用户和密码之间。我在某个地方犯了错误吗？

Answer 1

SUDO_COMMAND是sudo仅在由它启动的进程的环境中设置的环境变量（并由任何子进程继承）。如果运行sudo some-command arg1 arg2，SUDO_COMMAND则将包含到some-command, 和的绝对路径arg1 arg2。如果您运行sudo -s或sudo -i，则该变量将设置为启动的 shell。无论如何，您可能不会在由sudo.

例如：

$ sudo sh -c 'echo $SUDO_COMMAND'
/bin/sh -c echo $SUDO_COMMAND

或者：

$ sudo env
HOME=/home/muru
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin
TERM=xterm-256color
LANG=en_US.UTF-8
LC_NUMERIC=en_GB.UTF-8
LC_TIME=en_GB.UTF-8
LC_MONETARY=en_GB.UTF-8
LC_PAPER=en_GB.UTF-8
LC_NAME=en_GB.UTF-8
LC_ADDRESS=en_GB.UTF-8
LC_TELEPHONE=en_GB.UTF-8
LC_MEASUREMENT=en_GB.UTF-8
LC_IDENTIFICATION=en_GB.UTF-8
MAIL=/var/mail/root
LOGNAME=root
USER=root
USERNAME=root
SHELL=/bin/bash
SUDO_COMMAND=/usr/bin/env
SUDO_USER=muru
SUDO_UID=1000
SUDO_GID=1000

我注意到信息是有序的

我不知道哪个命令你使用，但你不能依靠的输出set，declare，env或者printenv是在一些命令。

Answer 2

这SUDO_COMMAND是一个环境变量，它设置为 sudo 运行的命令。

正如@muru 所提到的——如果sudo执行一个新的 shell——这个环境变量将显示在这个新的 shell 中

更多信息

man sudo 提供以下详细信息：

ENVIRONMENT
 sudo utilizes the following environment variables.  The security policy
 has control over the actual content of the command's environment.

 EDITOR           Default editor to use in -e (sudoedit) mode if neither
                  SUDO_EDITOR nor VISUAL is set.

 MAIL             Set to the mail spool of the target user when the -i
                  option is specified or when env_reset is enabled in
                  sudoers (unless MAIL is present in the env_keep list).

 HOME             Set to the home directory of the target user when the -i
                  or -H options are specified, when the -s option is
                  specified and set_home is set in sudoers, when
                  always_set_home is enabled in sudoers, or when env_reset
                  is enabled in sudoers and HOME is not present in the
                  env_keep list.

 LOGNAME          Set to the login name of the target user when the -i
                  option is specified, when the set_logname option is
                  enabled in sudoers or when the env_reset option is
                  enabled in sudoers (unless LOGNAME is present in the
                  env_keep list).

 PATH             May be overridden by the security policy.

 SHELL            Used to determine shell to run with -s option.

 SUDO_ASKPASS     Specifies the path to a helper program used to read the
                  password if no terminal is available or if the -A option
                  is specified.

 SUDO_COMMAND     Set to the command run by sudo.