运行“我是谁"在带有sudo的单个命令中不返回任何内容 [英] Running "who am i" in a single command with sudo doesnt return anything

问题描述

我正在尝试以以下方式在一行中运行我是谁"命令，但该命令不返回任何内容.

I am trying to run "who am i" command in a single line in the following way and it returns nothing.

echo $password | sudo -u user -S who am i

即使登录名命令也无法以这种方式工作.

Even logname command doesn't work in this way.

echo $password | sudo -u user -S logname

任何人都可以帮忙吗?

推荐答案

使用两个参数调用谁时，将激活 -m 标志.从手册页:

When who is invoked with two arguments, the -m flag is activated. From the manual page:

-m
    only hostname and user associated with stdin

在您的情况下，标准输入是管道，而不是终端，并且谁(或 logname )无法确定关联的用户.考虑以下shell命令片段:

In your case, the standard input is a pipe, rather than a terminal, and who (or logname) cannot determine the associated user. Consider this shell command snippet:

$ who am i
user   pts/11       2014-09-04 00:15
$ logname
user
$ echo | who am i
$ echo | logname
logname: no login name
$ 

来自 GNU Coreutils who.c 来源:

if (my_line_only)
  {
    ttyname_b = ttyname (STDIN_FILENO);
    if (!ttyname_b)
      return;
    if (STRNCMP_LIT (ttyname_b, DEV_DIR_WITH_TRAILING_SLASH) == 0)
      ttyname_b += DEV_DIR_LEN; /* Discard /dev/ prefix.  */
  }

由于 ttyname()在出现错误时会返回 NULL ，例如文件描述符不对应于终端( ENOTTY )，当 stdin 是管道时，who -m 将立即返回.

Since ttyname() returns NULL on errors, such as the file descriptor not corresponding to a terminal (ENOTTY), who -m will return immediately when stdin is a pipe.

对于 logname ，它的正确行为是返回 getlogin()函数返回的字符串.不幸的是， getlogin()手册页中的错误部分很清楚:

As for logname, its proper behavior is to return the string that would have been returned by the getlogin() function. Unfortunately, the bug section of the getlogin() manual page is quite clear:

请注意，glibc不遵循POSIX规范，而是使用stdin代替/dev/tty.一个错误.(其他最近的系统，如SunOS 5.8和HP-UX 11.11和FreeBSD 4.8都在重定向标准输入时也返回登录名.)

Note that glibc does not follow the POSIX specification and uses stdin instead of /dev/tty. A bug. (Other recent systems, like SunOS 5.8 and HP-UX 11.11 and FreeBSD 4.8 all return the login name also when stdin is redirected.)

底线:您可能应该更新代码以使用 hostname ，例如 id -un 或您的解释器可能会提供的其他任何方式来确定当前用户. who -m 及其朋友不是很容易预测-坦白地说， who 的输出与 ls 一样，具有明显的预期性对于人类，而不是机器.

Bottom line: you should probably update your code to use hostname and e.g. id -un or whatever other means your shell interpretter may offer to determine the current user. who -m and its friends are not very predictable - quite honestly the output of who, much like ls, has the distinct feel of being intended for humans, rather than machines.

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