Question

I have this simple ruby script:

redcricket@dev-006:~$ cat simple.rb  
#!/usr/local/bin/ruby

IO.popen 'ls -l', 'r+' do |f|
        puts f.gets
end

and when I run it the only output I get is this …

redcricket@dev-006:~$ ./simple.rb  
total 32

… what I expected was this …

redcricket@smp-mig-dev-006:~$ ls -l
total 32
drwxr-xr-x  4 redcricket co 4096 Dec  5 12:23 applications
-rw-r--r--  1 redcricket co  464 Oct  5 16:23 config
drwxr-xr-x 72 redcricket co 4096 Dec  5 15:11 docs
drwxr-xr-x  3 root    root  4096 Dec  5 12:14 oradiag_root
drwxr-xr-x  5 redcricket co 4096 Dec  5 16:22 platform
-rwxr-xr-x  1 redcricket co  373 Dec  5 16:30 process_yum_output.rb
-rwxr-xr-x  1 redcricket co 2159 Nov 28 16:24 SetupSSHPK.sh
-rwxr-xr-x  1 redcricket co  142 Dec  5 16:31 simple.rb

… I guess I need to iterate over f.gets somehow?

Thanks!

Answer 1

The Ruby IO#gets method just returns the next line of input from the IO object.

In order to get all of the lines you could call “gets” repeatedly until it’s nil, or call read to get the entire string, or readlines to get the lines of input in an array.

IO.popen('ls -l','r') { |f| puts $_ while f.gets }
IO.popen('ls -l','r') { |f| puts f.read }
IO.popen('ls -l','r') { |f| puts f.readlines }