在哪里可以找到SUDO_COMMAND环境变量？

我目前正在学习Ubuntu的Linux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信息，但找不到SUDO_COMMAND。清单是这样的：

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？

SUDO_COMMAND是一个环境变量，sudo仅在由它启动（并由任何子进程继承）的进程的环境中设置。如果你运行sudo some-command arg1 arg2，然后SUDO_COMMAND将包含的绝对路径some-command，和arg1 arg2。如果您运行sudo -s或sudo -i，则变量将设置为启动的外壳。无论如何，您可能不会在由开头的进程树之外看到它sudo。

例如：

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

要么：

$ 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

我注意到信息按顺序排列

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。

该SUDO_COMMAND是一个环境变量，其设置为须藤运行命令。

正如@muru所提到的-如果sudo执行新的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.