linux下如何查看已经登录用户
2011-01-20 15:28
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%Q
This is an alternative for double-quoted strings, when you have more quote characters in a string.Instead of putting backslashes in front of them, you can easily write:
The parenthesis “(…)” can be replaced with any other non-alphanumeric characters and non-printing characters (pairs), so the following commands are equivalent:
You can use also:
%q
Used for single-quoted strings.The syntax is similar to %Q, but single-quoted strings are not subject to expression substitution or escape sequences.
%W
Used for double-quoted array elements.The syntax is similar to %Q
%w
Used for single-quoted array elements.The syntax is similar to %Q, but single-quoted elements are not subject to expression substitution or escape sequences.
%x
Uses the ` method and returns the standard output of running the command in a subshell.The syntax is similar to %Q.
%r
Used for regular expressions.The syntax is similar to %Q.
%s
Used for symbols.It’s not subject to expression substitution or escape sequences.
Thanks, Ivan
This is an alternative for double-quoted strings, when you have more quote characters in a string.Instead of putting backslashes in front of them, you can easily write:
>> %Q(Joe said: "Frank said: "#{what_frank_said}"") => "Joe said: "Frank said: "Hello!"""
The parenthesis “(…)” can be replaced with any other non-alphanumeric characters and non-printing characters (pairs), so the following commands are equivalent:
>> %Q!Joe said: "Frank said: "#{what_frank_said}""! >> %Q[Joe said: "Frank said: "#{what_frank_said}""] >> %Q+Joe said: "Frank said: "#{what_frank_said}""+
You can use also:
>> %/Joe said: "Frank said: "#{what_frank_said}""/ => "Joe said: "Frank said: "Hello!"""
%q
Used for single-quoted strings.The syntax is similar to %Q, but single-quoted strings are not subject to expression substitution or escape sequences.
>> %q(Joe said: 'Frank said: '#{what_frank_said} ' ') => "Joe said: 'Frank said: '\#{what_frank_said} ' '"
%W
Used for double-quoted array elements.The syntax is similar to %Q
>> %W(#{foo} Bar Bar\ with\ space) => ["Foo", "Bar", "Bar with space"]
%w
Used for single-quoted array elements.The syntax is similar to %Q, but single-quoted elements are not subject to expression substitution or escape sequences.
>> %w(#{foo} Bar Bar\ with\ space) => ["\#{foo}", "Bar", "Bar with space"]
%x
Uses the ` method and returns the standard output of running the command in a subshell.The syntax is similar to %Q.
>> %x(echo foo:#{foo}) => "foo:Foo\n"
%r
Used for regular expressions.The syntax is similar to %Q.
>> %r(/home/#{foo}) => "/\\/home\\/Foo/"
%s
Used for symbols.It’s not subject to expression substitution or escape sequences.
>> %s(foo) => :foo >> %s(foo bar) => :"foo bar" >> %s(#{foo} bar) => :"\#{foo} bar"
Thanks, Ivan
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