Ruby frozen string literal pragma order caused error

Question

Given a file with Ruby 2.3.0p0:

#!/usr/bin/env ruby

# frozen_string_literal: true

# Exit cleanly from an early interrupt
Signal.trap("INT") { abort }

This is fine.

# frozen_string_literal: true

#!/usr/bin/env ruby

# Exit cleanly from an early interrupt
Signal.trap("INT") { abort }

will result in error:

syntax error near unexpected token `"INT"'
`Signal.trap("INT") { abort }'

Why?

how are you executing the file - ./filename.rb or ruby filename.rb ? — Frederick Cheung, Mar 17 '16 at 15:21
That is no Ruby error, it's from your shell. The [shebang](https://en.wikipedia.org/wiki/Shebang_(Unix)) has to be the initial line. Otherwise, the file is executed as a shell script. — Stefan, Mar 17 '16 at 15:28
Why does the error point to line 8 when there are only six lines? — sawa, Mar 17 '16 at 15:30
Following this question, I asked a related question: http://stackoverflow.com/questions/36065453 — sawa, Mar 17 '16 at 15:47
@sawa Sorry this is copied from a script, the number is not important, edited my question. — Juanito Fatas, Mar 18 '16 at 02:40

Stefan · Accepted Answer · 2016-03-17T16:02:50.260

A shebang has to appear on the file's initial line.

A file test.rb containing:

#!/usr/bin/env ruby    
# foo bar
puts "hello from #{RbConfig.ruby}"

will be run via Ruby:

$ ./test.rb
hello from /.../ruby-2.3.0/bin/ruby

But if test.rb contains: (1st and 2nd line swapped)

# foo bar
#!/usr/bin/env ruby
echo "hello from $SHELL"

it will be run as an ordinary shell script:

$ ./test.rb
hello from /.../bin/zsh

Therefore, the error you are getting is no Ruby error, it's from your shell.

1 Answers1