I'm writing a Mac OS program, and I have the following lines:
os.execute("cd ~/testdir")
configfile = io.open("configfile.cfg", "w")
configfile:write("hello")
configfile:close()
The problem is, it only creates the configfile in the scripts current directory instead of the folder I have just cd' into. I realised this is because I'm using a console command to change directory, then direct Lua code to write the file. To combat this I changed the code to this:
configfile = io.open("~/testdir/configfile.cfg", "w")
However I get the following result:
lua: ifontinst.lua:22: attempt to index global 'configfile' (a nil value)
stack traceback:
ifontinst.lua:22: in main chunk
My question is, what's the correct way to use IO.Open to create a file in a folder I have just created in the users home directory?
I appreciate I'm making a rookie mistake here, so I apologise if you waste your time on me.
You have problems with ~ symbol. In your os.execute("cd ~/testdir") is the shell who interprets the symbol and replaces it by your home path. However, in io.open("~/testdir/configfile.cfg", "w") is Lua who receives the string and Lua doesn't interprets this symbol, so your program tries to open a file in the incorrect folder. One simple solution is to call os.getenv("HOME") and concatenate the path string with your file path:
configfile = io.open(os.getenv("HOME").."/testdir/configfile.cfg", "w")
In order to improve error messages I suggests you to wrap io.open() using assert() function:
configfile = assert( io.open(os.getenv("HOME").."/testdir/configfile.cfg", "w") )
Related
I got a method where I use Dir.chdir(File.dirname(__FILE__)) inside. I am using it so that I can run the ruby file from anywhere and not get this error: No such file or directory # rb_sysopen - 'filename' (Errno::ENOENT).
Using the method for the first time works fine but using it for the second time throws an error. See method and exact error below.
def meth(string)
Dir.chdir(File.dirname(__FILE__))
hash = JSON.parse(File.read("file.json"))
# do something with hash and string
# return some value
end
meth("first string") # this returns what is expected
meth("second string") # this second usage of the method throws the error
Error sample pinpointing the line where I used Dir.chdir(File.dirname(__FILE__)):
dir/decoder.rb:44:in `chdir': No such file or directory # dir_s_chdir - lib (Errno::ENOENT)
Not sure if OS plays a role here, I am using an m1 BigSur on version 11.2.3.
Why is this happening?
What needs to be done so that the method` can be used as much as needed without running into the error?
Your problem here seems to be that __FILE__ is a relative path like dir/decoder.rb and that path becomes invalid after the first time Dir.chdir is used, because that command changes the working directory of your entire Ruby process. I think the solution would be to do something like this in your decoder.rb file:
DecoderDir = File.realpath(File.dirname(__FILE__))
def meth
Dir.chdir(DecoderDir)
# ...
end
I'm guessing that the first time the Ruby interpreter processes the file, that is early enough that the relative path in __FILE__ still refers to the right place. So, at that time, we generate an absolute path for future use.
By the way, a well-behaved library should not run Dir.chdir because it will affect all use of relative paths throughout your entire Ruby process. I pretty much only run Dir.chdir once and I run it near the beginning of my top-level script. If you're making a reusable library, you might want to do something like this to calculate the absolute path of the file you want to open:
DecoderJson = File.join(DecoderDir, 'file.json')
I'm trying to load a C shared library within Ruby using Fiddle.
Here is a minimal example:
require 'fiddle'
require 'fiddle/import'
module Era
extend Fiddle::Importer
dlload './ServerApi.so'
extern 'int era_init_lib()'
extern 'void era_deinit_lib()'
extern 'int era_process_request(const char* request, char** response)'
extern 'void era_free(char* response)'
end
Era.era_init_lib
begin
# ...
ensure
Era.era_deinit_lib
end
The shared library loads without issues. However when I call Era.era_init_lib it tries to load additional libraries (Network.so and Protobuf.so). I have these file located in the current working directory (in the same directory as ServerApi.so).
However when I try to execute the code above I receive the following error:
! Failed to load library: /home/username/.rvm/rubies/ruby-2.6.5/bin/Network.so, error: /home/username/.rvm/rubies/ruby-2.6.5/bin/Network.so: cannot open shared object file: No such file or directory
If I place the file at the location the error describes everything works fine.
My guess is that the C working directory of fiddle is different from the Ruby working directory. I would like to keep the project files within the project and not in the Ruby installation directory.
How can I use Network.so from my project folder?
All the *.so files are provided by a third-party. I do not have the source and as a result cannot change these files. The function signatures are provided by the documentation.
Searching for Network.so in the strace gives me these results:
readlink("/proc/self/exe", "/home/username/.rvm/rubies/ruby-2."..., 4096) = 44
openat(AT_FDCWD, "/home/username/.rvm/rubies/ruby-2.6.5/bin/Network.so", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
futex(0x7fcc16666d90, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7fcc16b44520, FUTEX_WAKE_PRIVATE, 2147483647) = 0
write(2, "! Failed to load library: ", 26! Failed to load library: ) = 26
write(2, "/home/username/.rvm/rubies/ruby-2."..., 50/home/username/.rvm/rubies/ruby-2.6.5/bin/Network.so) = 50
write(2, ", error: ", 9, error: ) = 9
write(2, "/home/username/.rvm/rubies/ruby-2."..., 109/home/username/.rvm/rubies/ruby-2.6.5/bin/Network.so: cannot open shared object file: No such file or directory) = 109
write(2, "\n", 1) = 1
I've also written a C script which does the same thing which works perfectly fine when the files are dropped into the same directory. So it might be the fault of the library, which I assume checks the location of the current running program, then tries to load the library from that folder. This would explain the behavior when ran as a Ruby script (since it runs as part of the Ruby program), whereas a C binary runs standalone.
For those that want to re-create the (Linux) issue. You can download the necessary files from here. Which gives you the server-linux-x86_64.sh file.
Supported distros are: Suse, Ubuntu, Debian, Red Hat and CentOS but others may also work fine.
You can either run the installer, which should place the files in /opt/eset/RemoteAdministrator/Server. Or, assuming most of you don't want to install the full application you can run the following command:
sed '1,/^# Start of TAR\.GZ file #$/d' server-linux-x86_64.sh | sed '1d' > server-linux-x86_64.tar.gz
Which removes all the installer instructions from the .sh file and only leaves the binary .tar.gz data, writing it to server-linux-x86_64.tar.gz.
Copy the files ServerApi.so, Protobuf.so and Network.so into a directory of your liking. Create a Ruby script (with the question code) in the same directory and run the script.
Because ServerApi.so checks /proc/self/exe for the location of all subsequent files to load, and it is very difficult to modify this target by normal means, it is easier to just modify ServerApi.so itself so that it uses something else besides proc for the source.
If we run strings ServerApi.so, we can verify that the location to check is stored inside a string in ServerApi.so:
strings ServerApi.so | grep 'proc/self/exe'
B/proc/self/exe
So now all we need to do is modify this string to something else that works for us.
The easiest way to modify the string is to replace it with something that is exactly the same length as the original. This way we do not have to worry about changing the end-of-string zero padding or accidentally changing the total size of ServerApi.so.
Here we can see a suitable candidate could be /tmp/scriptexe:
/proc/self/exe
/tmp/scriptexe <- same length
So let's do that:
sed -e 's/proc\/self\/exe/tmp\/scriptexe/' ServerApi.so > ServerApi_Mod.so
Now we can verify the change:
strings ServerApi_Mod.so | grep scriptexe
B/tmp/scriptexe
Next we need to create /tmp/scriptexe to actually point to our Ruby script:
ln -s /the/full/path/to/our/ruby/script.rb /tmp/scriptexe
Then we modify our script:
dlload './ServerApi_Mod.so
Now we can run it as normal:
ruby script.rb
And everything should work.
If we read the strace output we see that the library obtains the current executable location from /proc/self/exe, and then searches subsequent libraries from there.
/proc/self/exe is not easily modifiable, but by using a hard link to a Ruby executable in the current directory we can trick it to point to a new folder.
Problem is making a hard link requires root.
In any case, here is a self-contained solution (note that it will ask for root password the first time you run it, in order to create the hard link).
Put this at the top of your script:
# Obtain path to current executable
exe = File.readlink("/proc/self/exe")
# Check if we are running the hard-liked version
if !exe.match /localruby/
if !File.exist?('localruby')
# Create a hard link to the current Ruby exe using sudo
system("sudo ln #{exe} localruby")
end
puts "Restarting..."
# In order to prevent infinite busy loop in case of some mishap
sleep 1
# Rerun self using the hard-linked Ruby executable.
# This will make /proc/self/exe point to the hard-link, which then
# allows the ESET library to search for .so files in current folder.
exec('./localruby', File.expand_path(__FILE__))
end
require 'fiddle'
require 'fiddle/import'
# ...rest of your script goes here...
A simple solution without any extra Ruby code is to just create the hard link manually, and then always run the script with ./localruby myscript.rb, instead of using the normal ruby myscript.rb.
I have a file called backup.lua, which the program should write to every so often in order to backup its status, in case of a failure.
The problem is that the program writes the backup.lua file completely fine first-time round, but any other times it refuses to write to the file.
I tried removing the file while the program was still open but Windows told me that the file was in use by 'CrysisWarsDedicatedServer.exe', which is the program. I have told the host Lua function to close the backup.lua file, so why isn't it letting me modify the file at will after it has been closed?
I can't find anything on the internet (Google actually tried to correct my search) and the secondary programmer on the project doesn't know either.
So I'm wondering if any of you folks know what we are doing wrong here?
Host function code:
function ServerBackup(todo)
local write, read;
if todo=="write" then
write = true;
else
read = true;
end
if (write) then
local source = io.open(Root().."Mods/Infinity/System/Read/backup.lua", "w");
System.Log(TeamInstantAction:GetTeamScore(2).." for 2, and for 1: "..TeamInstantAction:GetTeamScore(1))
System.LogAlways("[System] Backing up serverdata to file 'backup.lua'");
source:write("--[[ The server is dependent on this file; editing it will lead to serious problems.If there is a problem with this file, please re-write it by accessing the backup system ingame.--]]");
source:write("Backup = {};Backup.Time = '"..os.date("%H:%M").."';Backup.Date = '"..os.date("%d/%m/%Y").."';");
source:write(XFormat("TeamInstantAction:SetTeamScore(2, %d);TeamInstantAction:SetTeamScore(1, %d);TeamInstantAction:UpdateScores();",TeamInstantAction:GetTeamScore(2), TeamInstantAction:GetTeamScore(1) ));
source:close();
for i,player in pairs(g_gameRules.game:GetPlayers() or {}) do
if (IsModerator(player)) then
CMPlayer(player, "[!backup] Completed server backup.");
end
end
end
--local source = io.open(Root().."Mods/Infinity/System/Read/backup.lua", "r"); Can the file be open here and by the Lua scriptloader too?
if (read) then
System.LogAlways("[System] Restoring serverdata from file 'backup.lua'");
--source:close();
Backup = {};
Script.LoadScript(Root().."Mods/Infinity/System/Read/backup.lua");
if not Backup or #Backup < 1 then
System.LogAlways("[System] Error restoring serverdata from file 'backup.lua'");
end
end
end
Thanks all :).
Edit:
Although the file is now written to the disk fine, the system fails to read the dumped file.
So, now the problem is that the "LoadScript" function isn't doing what you expect:
Because I'm psychic, i have divined that you're writing a Crysis plugin, and are attempting to use it's LoadScript API call.
(Please don't assume everyone here would guess this, or be bothered to look for it. It's vital information that must form part of your questions)
The script you're writing attempts to set Backup - but your script, as written - does not separate lines with newline characters. As the first line is a comment, the entire script will be ignored.
Basicallty the script you've written looks like this, which is all treated as a comment.
--[[ comment ]]--Backup="Hello!"
You need to write a "\n" after the comment (and, I'd recommend in other places too) to make it like this. In fact, you don't really need block comments at all.
-- comment
Backup="Hello!"
I'm trying to write a Sinatra app that reads in a list from a file, and then spits back a random item from that list.
I'm having trouble figuring out the path to the file to read it, though. Sinatra says 'no such file or directory' when I try to load an item in my browser:
Errno::ENOENT at /wod
No such file or directory - http://localhost:4567/listing.txt
Here is the code:
require 'sinatra'
#list
get /item
puts read_list[rand(#list.size)]
end
def read_list
File.open('listing.txt', 'r').readlines
end
I have the file in /public, which the Sinatra README says is the default location for hosting static files. Furthermore, if I put it in /public I can navigate to localhost:4567/listing.txt and read the file in the browser.
A couple things I noticed:
get /item
isn't correct, it should be:
get '/item' do
If you start your code inside the same directory the Ruby code is in, the current working-directory will be ".", which is where Ruby will look when trying to:
File.open('listing.txt', 'r').readlines
Ruby will actually use './listing.txt' as the path. That's OK if you manually launch the code from the root directory of the application, but that doesn't work well if you try to launch it from anywhere else.
It's better to be explicit about the location of the file when you're actually trying to load something for use with a web server. Instead of relying on chance, there are a couple things you can do to help make it more bullet-proof. Consider this:
def read_list
running_dir = File.dirname(__FILE__)
running_dir = Dir.pwd if (running_dir == '.')
File.open(running_dir + '/public/listing.txt', 'r').readlines
end
File.dirname gets the path information from __FILE__, which is the absolute path and name of the current file running. If the application was started from the same directory as the file, that will be ., which isn't what we want. In that case, we want the absolute path of the current working-directory, which Dir.pwd returns. Then we can append that to the path of the file you want, from the root of the application.
You'll need to do File.read('public/listing.txt', 'r') to get what you want here.
File.open isn't part of Sinatra and doesn't know to look in a specific place for static files, so it just looks in the current working directory.
How can I get the path for the last created file in a directory using Ruby?
I think this is fairly brief:
Dir.glob(File.join(path, '*.*')).max { |a,b| File.ctime(a) <=> File.ctime(b) }
Dir.entries("testdir").reject{|f| f== '.' || f=='..'}.sort_by{|f| File.ctime(f)}.last
you can use the dir class to list all files and check the ctime or atime of the file object (ctime is the time the file was changed the last time, atime is the time the file was accessed the last time)
Dir.foreach("testdir") {|f| puts File.ctime(x) }
Dir.glob(root_path + ".").map{ |file| [file,File.ctime(file)]}.max.first
I added this method to my supermanpatches.rb file inside of railsapp/config/initializers to open my latest generated migration (in TextMate) without having to copy and paste the filename or anything like that:
def latestmigration
`mate db/migrate/#{Dir.glob(File.join(Rails.root, 'db', 'migrate', '*.rb')).max { |a,b| File.ctime(a) <=> File.ctime(b)} }`
end
‡: (FYI for ruby/rails beginners, initializer code is omnipresent and requires no class-to-filename scoping to be accessible from anywhere within rails)
NOTE: With windows (or mac) you could use the vim command instead of the mate command, and sublimetext can be configured to do this too, I think its called the subl command. mate & subl don't work by default though I think, so you have to set that up first