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令牌“$$”代表什么？在 Ruby 中是什么意思？

发布于 2024-11-19 03:34:21 字数 69 浏览 2 评论 0原文

我在 mini_magick 库的 makeTempname() 的 image_temp_file.rb 中看到这个变量。

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不羁少年 2024-11-26 03:34:21

$ 开始对全局变量的引用。程序通常会定义类似 $name 的内容，并且系统预定义了许多信息和控制引用。

$$ 特别是进程 ID。

 
    $name program-defined global variable
    $!  latest error message
    $@  location of error
    $_  string last read by gets
    $.  line number last read by interpreter
    amp;  string last matched by regexp
    $~  the last regexp match, as an array of subexpressions
    $n  the nth subexpression in the last match (same as $~[n])
    $=  case-insensitivity flag
    $/  input record separator
    $\  output record separator
    $0  the name of the ruby script file
    $*  the command line arguments
    $  interpreter's process ID
    $?  exit status of last executed child process

The $ begins a reference to a global variable. Programs will typically define something like $name and the system predefines a number of information and control references.

$$, in particular, is the process ID.

 
    $name program-defined global variable
    $!  latest error message
    $@  location of error
    $_  string last read by gets
    $.  line number last read by interpreter
      string last matched by regexp
    $~  the last regexp match, as an array of subexpressions
    $n  the nth subexpression in the last match (same as $~[n])
    $=  case-insensitivity flag
    $/  input record separator
    $\  output record separator
    $0  the name of the ruby script file
    $*  the command line arguments
    $  interpreter's process ID
    $?  exit status of last executed child process

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久光 2024-11-26 03:34:21

它是运行您所在脚本的 Ruby 解释器的进程 ID。例如：

[/tmp] Ψ irb
ruby> $
 => 16045                          # We're in process id 16045.
ruby> ^Z
[1]+  Stopped irb                  # Let's stop irb so we can
                                   # verify that it's the right pid.

[/tmp] Ψ ps aux | grep -inr 16045  # grep across all processes.
80:johnf    16045  ... irb         # There it is!

It's the process ID of the Ruby interpreter running the script you're in. For example:

[/tmp] Ψ irb
ruby> $
 => 16045                          # We're in process id 16045.
ruby> ^Z
[1]+  Stopped irb                  # Let's stop irb so we can
                                   # verify that it's the right pid.

[/tmp] Ψ ps aux | grep -inr 16045  # grep across all processes.
80:johnf    16045  ... irb         # There it is!

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