"ruby​​中的哪个":检查程序在$ PATH中是否存在来自ruby的内容 [英] "which in ruby": Checking if program exists in $PATH from ruby

问题描述

我的脚本在很大程度上依赖于外部程序和脚本. 我需要确保我需要调用的程序存在. 手动地，我会在命令行中使用哪个"来检查.

my scripts rely heavily on external programs and scripts. I need to be sure that a program I need to call exists. Manually, I'd check this using 'which' in the commandline.

$PATH中的内容是否等同于File.exists??

Is there an equivalent to File.exists? for things in $PATH?

(是的，我想我可以解析%x[which scriptINeedToRun]，但这不是超级优雅.

(yes I guess I could parse %x[which scriptINeedToRun] but that's not super elegant.

谢谢！ 扬尼克

更新:这是我保留的解决方案:

UPDATE: Here's the solution I retained:

 def command?(command)
       system("which #{ command} > /dev/null 2>&1")
 end

---

更新2:一些新的答案出现了-至少其中一些提供了更好的解决方案.

更新3: ptools gem 为File类添加了"which"方法. h3>

---

UPDATE 2: A few new answers have come in - at least some of these offer better solutions.

Update 3: The ptools gem has adds a "which" method to the File class.

推荐答案

真正的跨平台解决方案，在Windows上可以正常使用:

True cross-platform solution, works properly on Windows:

# Cross-platform way of finding an executable in the $PATH.
#
#   which('ruby') #=> /usr/bin/ruby
def which(cmd)
  exts = ENV['PATHEXT'] ? ENV['PATHEXT'].split(';') : ['']
  ENV['PATH'].split(File::PATH_SEPARATOR).each do |path|
    exts.each do |ext|
      exe = File.join(path, "#{cmd}#{ext}")
      return exe if File.executable?(exe) && !File.directory?(exe)
    end
  end
  nil
end

这不使用主机操作系统嗅探，而是遵守$ PATHEXT，它列出了Windows上可执行文件的有效文件扩展名.

This doesn't use host OS sniffing, and respects $PATHEXT which lists valid file extensions for executables on Windows.

炮轰到which可以在许多系统上使用，但不是全部.

Shelling out to which works on many systems but not all.

这篇关于"ruby​​中的哪个":检查程序在$ PATH中是否存在来自ruby的内容的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！