How to get the current running binary root realpath from Crystal source code

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1

Assume i built my binary from ~/foo/ use shards build, i will get a binary like this: ~/foo/bin/foo, then i copy foo into ~/utils/bin/, so, the realpath of foo should be ~/utils/bin/foo.

So, i there a way to get the above ~/utils/bin/foo from Crystal source dynamically when running foo?

For my use case, i want to search a SQLite db file, it should be created on the same folder as foo binary, thanks.

2

This should get you the absolute path. Remove expand if you don’t need it to be absolute.

Path[PROGRAM_NAME].expand.dirname
3

Hi, It’s seem like not work when run binary directly in the $PATH, following is a example, my binary name is 1, and this file copy to ~/utils/bin which is added in the $PATH.

 ╰─ $ pwd
/home/zw963

 ╰─ $ 1
Path[PROGRAM_NAME].expand.dirname # => "/home/zw963"

 ╰─ $ which -a 1
/home/zw963/utils/bin/1
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4

And this is why I shouldn’t answer questions 10 minutes after waking up :laughing:

Here’s a few other ways that I tested on my system.

# Method 1: Check the /proc filesystem if the OS has one.
puts File.readlink("/proc/self/exe") # Linux
#puts File.readlink("/proc/curproc/file") # FreeBSD

# Method 2: use PROGRAM_NAME or $PATH
argv0 = Path[PROGRAM_NAME]
if argv0.absolute?
  # Can use argv0
  puts "From absolute: #{argv0}"
elsif argv0.to_s.includes?('/')
  # Relative path, expand it
  puts "From relative: #{argv0.expand}"
else
  # Search PATH
  puts "Found in path?: #{Process.find_executable(argv0.basename)}"
end

Just take the Path.dirname as-needed.

5

Thanks, i learn a lot from your answer.

The method 1 works on my Arch linux, but considering possible compatibility, not sure if File.readlink("/proc/curproc/file") works on mac OS, i select the method 2.

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6

Process.executable_path

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7

Wow, Works like a charm!

8

As the document said:

Returns nil if the file can’t be found.

When the file can’t be found and Process.executable_path return nil?

9

If the executable file doesn’t exist (anymore).

Example:

Process.executable_path.try{|path| File.delete(path) }
Process.executable_path # => nil
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