Backquote and variables

I am trying to construct a command line to be executed using backquote
`` notation. i.e. capturing the output to a string

e.g.

#!/usr/bin/ruby -w
file = “/etc/motd”
string = "cat " + file
puts string

% ruby test.rb
sh: line 1: cat : command not found

This doesn’t work. It appears that everything between the backquotes is
treated as a quoted string. i.e. no variable substitution takes place.

How can I work around this?

[email protected] wrote:

I am trying to construct a command line to be executed using backquote `` notation. i.e. capturing the output to a string

e.g.

#!/usr/bin/ruby -w
file = “/etc/motd”
string = "cat " + file

string = #{"cat "} + file

On 10/24/06, [email protected] [email protected]
wrote:

sh: line 1: cat : command not found

This doesn’t work. It appears that everything between the backquotes is treated as a quoted string. i.e. no variable substitution takes place.

How can I work around this?

The backtick string is treated like a double-quote. Therefore, you can
do this:
file = ‘/etc/motd’
motd = cat #{file}
puts motd

Joel VanderWerf wrote:

string = #{"cat "} + file

Oops, I didn’t really read your example. I assumed you were trying to
get the command name interpolated in the string. Wilson answered your
question.

If you wanted to interpolate both, you could do this:

cmd=“cat”
file="/etc/motd"
motd = #{cmd} #{file}

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