我正在尝试将$ stdout设置为临时写入文件,然后返回文件。
test.rb :
old_stdout = $stdout
$stdout.reopen("mytestfile.out",'w+')
puts "this goes in mytestfile"
$stdout= old_stdout
puts "this should be on the console"
$stdout.reopen("mytestfile1.out",'w+')
puts "this goes in mytestfile1:"
$stdout = old_stdout
puts "this should be back on the console"
这是输出。
ruby test.rb => no output on the console
cat mytestfile.out
this goes in mytestfile
this should be on the console
cat mytestfile1.out
this goes in mytestfile1:
this should be back on the console
我不确定为什么$ stdout没有重置为控制台?
答案 0 :(得分:7)
在更改$stdout
之前调用old_stdout = $stdout.dup
$stdout.reopen("mytestfile.out",'w+')
puts "this goes in mytestfile"
$stdout = old_stdout.dup
puts "this should be on the console"
$stdout.reopen("mytestfile1.out",'w+')
puts "this goes in mytestfile1:"
$stdout = old_stdout
puts "this should be back on the console"
可以解决此问题:
ruby test.rb
# => this should be on the console
# => this should be back on the console
cat mytestfile.out
# => this goes in mytestfile
cat mytestfile1.out
# => this goes in mytestfile1
输出:
# Runs a block of code while blocking stdout.
# Note that /dev/null should be changed to NUL on Windows.
def silence_stdout(log = '/dev/null')
old = $stdout.dup
$stdout.reopen(File.new(log, 'w'))
yield
$stdout = old
end
以下是我通常将此功能打包到函数中的方法:
silence_stdout 'mytestfile.out' do
puts "this goes in mytestfile"
end
puts "this should be on the console"
silence_stdout 'mytestfile1.out' do
puts "this goes in mytestfile1"
end
puts "this should be back on the console"
用法:
{{1}}
编辑:正如另一张海报所提到的,只有在使用纯Ruby代码时才需要使用reopen。上面的函数既可以使用纯Ruby代码,也可以使用例如写入STDOUT的C扩展。
答案 1 :(得分:3)
如果您只是使用Ruby代码,则无需使用reopen
。 puts
和其他Ruby方法将使用$stdout
的当前值,因此您可以重新分配它。
old_stdout = $stdout
$stdout = File.new("mytestfile.out",'w+')
puts "this goes in mytestfile"
$stdout = old_stdout
puts "this should be on the console"
$stdout = File.new("mytestfile1.out",'w+')
puts "this goes in mytestfile1:"
$stdout = old_stdout
puts "this should be back on the console"
如果您正在执行类似创建子进程的操作(例如使用reopen
)并希望子输出转到别处,或者您有一个直接写入的扩展名,则只需要使用fork
标准输出而不使用Ruby的$stdout
全局。
在您的代码中,当您致电reopen
时,您正在重定向 {/ 1>}和$stdout
,因为它们都只是对同一IO对象的引用,这就是为什么在将old_stdout
分配回old_stdout
时,您无法将输出恢复到控制台。