使用 ps ef 或 ps -ef 哪个？

Question

我看到ps ef和之间的输出存在差异ps -ef。有什么区别，两个命令都正确还是首选？

Answer 1

man ps 说：

This version of ps accepts several kinds of options:

1   UNIX options, which may be grouped and must be preceded by a
    dash.
2   BSD options, which may be grouped and must not be used with a
    dash.
3   GNU long options, which are preceded by two dashes.

因此，ef使用 BSDe和f选项，并-ef使用 Unix-e和-f选项。这些是不同的（部分SIMPLE PROCESS SELECTION，OUTPUT FORMAT CONTROL和OUTPUT MODIFIERS分别地）：

   -e     Select all processes.  Identical to -A.
   -f     Do full-format listing. This option can be combined with many
          other UNIX-style options to add additional columns.  It also
          causes the command arguments to be printed.  When used with
          -L, the NLWP (number of threads) and LWP (thread ID) columns
          will be added.  See the c option, the format keyword args, and
          the format keyword comm.

   e      Show the environment after the command.

   f      ASCII art process hierarchy (forest).

显然，您没有使用ef选项选择所有进程，而是使用默认的进程列表以及一些其他格式：

By default, ps selects all processes with the same effective user ID
(euid=EUID) as the current user and associated with the same terminal
as the invoker.  It displays the process ID (pid=PID), the terminal
associated with the process (tname=TTY), the cumulated CPU time in
[DD-]hh:mm:ss format (time=TIME), and the executable name (ucmd=CMD).
Output is unsorted by default.

The use of BSD-style options will add process state (stat=STAT) to
the default display and show the command args (args=COMMAND) instead
of the executable name.  You can override this with the PS_FORMAT
environment variable. The use of BSD-style options will also change
the process selection to include processes on other terminals (TTYs)
that are owned by you; alternately, this may be described as setting
the selection to be the set of all processes filtered to exclude
processes owned by other users or not on a terminal.

你应该使用哪个？你想对输出做什么？

另外，请参阅该EXAMPLES部分（它确实列出了-ef相当突出的内容，并且根本不使用 BSDe选项）：

EXAMPLES

   To see every process on the system using standard syntax:
      ps -e
      ps -ef
      ps -eF
      ps -ely

   To see every process on the system using BSD syntax:
      ps ax
      ps axu

   To print a process tree:
      ps -ejH
      ps axjf

Answer 2

看man ps（你系统上的那个，网上可以有不同的解释）。

This version of ps accepts several kinds of options:

   1   UNIX options, which may be grouped and must be preceded by a dash.
   2   BSD options, which may be grouped and must not be used with a dash.
   3   GNU long options, which are preceded by two dashes.

所以第一种方法 ( ps ef) 是 BSD 风格，手册页继续

使用 BSD 样式的选项会将进程状态 (stat=STAT) 添加到默认显示中，并显示命令 args (args=COMMAND) 而不是可执行文件名称。您可以使用 PS_FORMAT 环境变量覆盖它。使用 BSD 风格的选项也会改变进程选择，以包括你拥有的其他终端 (TTY) 上的进程；或者，这可以描述为将选择设置为所有进程的集合，这些进程被过滤以排除其他用户拥有的进程或不在终端上的进程。These effects are not considered when options are described as being "identical" below, so -M will be considered identical to Z and so on.

所以两者都是有效的命令，但它们没有显示相同的信息。