Do any C++ GNU standalone classes exist which handle paths cross platform? My applications build on Windows and LInux. Our configuration files refer to another file in a seperate directory. I'd like to be able to read the path for the other configuration file into a class which would work on both Linux or Windows.
Which class would offer the smallest footprint to translate paths to use on either system? Thanks
Unless you're using absolute paths, there's no need to translate at all - Windows automatically converts forward slashes into backslashes, so if you use relative paths with forward slash path separators, you'll be golden. You should really avoid absolute paths if at all possible.
try boost::filesystem
Filesystem library in boost will probably help you.
There are many ways, IMHO the correct answer is to redesign your program to avoid manipulating paths. I posted an answer here: https://stackoverflow.com/a/40980510/2345997 which is relevant.
ways:
Add a command line option which allows a user to specify the path in question instead of reading it from a config file.
Add a command line option so that the user can specify a base path. Paths in the config file will be interpreted as located under this base path.
Split your config file into three. One file will have cross platform configuration, another file will have windows only configuration and a final file will have Linux only configuration. Then the user can specify the correct path for both Windows and Linux. On windows your program will read the cross-platform config file and the windows only config file. On Linux it will read the cross-platform file and the Linux only config file.
Add preprocessing to your config file parsing. This will allow you to have one config file where the user can make your program ignore some of the lines in the file depending on which OS the program is running on. Therefore, the user will be able to specify the path to the file twice. Once for Linux, and once for Windows.
Change the design so that the files are always located in the same directory as your executable - then the user only specifies file names in the config file rather than paths to files.
Use a simple function that switches "/" to "\". Then document to the user that they must specify paths as Linux paths and this transformation will be applied for windows.
Create your own path mini-language for this and document it to the user. E.g: "/" - specifies a directory separator, {root} - expands to the root of the filesystem, {cwd} - expands to the current directory, {app} - expands to the path to your application etc... Then the user can specify file paths like: {root}/myfiles/bob.txt on both platforms.
Some paths will work on both platforms. E.g: relative paths like ../my files/bill.txt. Restrict your application to only work with these paths. Document this limitation and how your application handles paths to the user.
Related
I have a c++ project that I would like to send to someone in executable form. The issue is the program must read from a .txt that I created (specific deliminators). Currently my program reads from a file path that is specific to my computer,
parseFile("/Users/David/Desktop/FinalProject/Store.txt");
How could I package the .txt file and the executable file together, where the exec. reads specifically from the that .txt on anyone's machine?
Note: I am using Xcode
Change your programs to receive 'file path' as a parameter. Write a note(ReadMe) with the program to specify the file format and added a sample data file with the package
tl;dr: if you just put the text file in the same folder with your executable, you can open it with parseFile("Store.txt");
In most runtime implementations, there is a notion of a "working directory." When you open up an executable via the graphical shell (by double clicking it or something to that effect) the working directory is the same as the directory the executable is in.
Now, if you try to open a file in your program via a path that isn't fully qualified, then the path that gets used will be relative to the working directory.
A fully qualified path is a discrete path that points to a single entity in your filesystem. "/Users/David/Desktop/FinalProject/Store.txt" is one such example, as it starts at root (/ on *nix, DriveLetter:\ on Windows) and says exactly which directories you need to traverse to get to your file.
A path that is not fully qualified (which basically means that it doesn't start at the root of your filesystem) can be used to perform relative file addressing. Most runtimes will assume that any path that is not fully qualified is meant to be relative to the working directory, which basically means that the path that actually gets opened is the result of concatenating your provided path to the end of the working directory.
As an example, if you opened your binary, which is stored as /Users/David/Desktop/FinalProject/a.exe, then the working directory would be set to /Users/David/Desktop/FinalProject/. If your program then tried to open "Store.txt", the runtime would see that you're trying to open a path that isn't fully qualified, so it would assume you meant to open a file relative to the working directory, which would then be /Users/David/Desktop/FinalProject/ + Store.txt, which would be /Users/David/Desktop/FinalProject/Store.txt.
The nice thing about this is that if you move your binary, the working directory moves too. if you move a.exe along with Store.txt to /Users/David/Desktop/FinalProject(copy)/, then when you open /Users/David/Desktop/FinalProject(copy)/a.exe, the working directory will be /Users/David/Desktop/FinalProject(copy)/ now, and now when you call parseFile("Store.txt"), it will instead open up /Users/David/Desktop/FinalProject(copy)/Store.txt. This holds true when moving to other computers, too.
It's worth noting that if your binary is run from a command line utility, the working directory will often be the directory the command line shell is in, rather than the executable's directory. It is, however, a part of the C standard that the first command line parameter to main() should be the name of the executable, and most implementations supply you with the fully qualified path. With some minimal parsing, you can use that to determine what path to use as a base for addressing files.
I'm new to deploying programs written in C/C++ on Linux and I'm wondering what you'd do in this situation.
I have a binary file (compiled with GNU Make) that needs to read a config file (such as myprogram.conf). But when I write a Makefile to deploy this file to /usr/bin/, where should the config file go? And how does the executable know where it is?
You have endless options, but the best way depends on a couple of things. First, is it a user-specific configuration file, or is it global to all users?
If it's user specific, you could, for example, keep it in ~/.myprogram/config.file and have the program check there. As a service to your users, it's up to you to decide what to do if it's not found -- perhaps copy a default config there from somewhere else, or generate a default, or use hard-coded default options, or display a configuration wizard, or just fail. That's entirely up to you.
If it's global, the traditional place to put it on Linux is in /etc, e.g. /etc/config.file or /etc/myprogram/config.file. See Linux File System Structure. You will generally always have a /etc on Linux. Handling a situation where the file does not exist is the same as above - there's no "right" way to handle that, it's based purely on how convenient you want to make it for a user.
What I usually do for global config files is put them in /etc/wherever on install, have the program default to loading the config file from /etc/wherever, but also give a command line option to override the configuration file (especially useful for testing or other situations).
What I usually do to handle missing config files depends entirely on the application. I'll generally either have hard-coded defaults (if that's appropriate) or simply fail and direct the user to some documentation describing a config file (which I find adequate in situations where my installer installs a config file).
Hope that helps.
It kind of depends on what the configuration parameters are, and whether they are "per system" or "per user" or "per group" or ...
System configurations typically live somewhere in /etc/.... In the same directory that the program lives is a very good place too.
User confgiurations, in the home directory of the user.
Group configurations are the trickiest, as you'll probably need to come up with a scheme where there is a configuration file per "group". /etc/myprog/groups/<groupname>/config or something similar would work.
On Linux, the usual location for configuration files is '/etc', so it is acceptable to deploy a configuration file like /etc/myprog.conf. That requires root privileges however. Other good options include putting a configuration file in the user's home directory, making it something like ~/.myprog.conf or ~/.myprog/.conf to use a folder where you can have several config files, a cache or something else that you want.
As for how the executable knows where the file is, one solution is to look for the file in several common locations. For example, if you decided to place your config in the user's home directory, look for it there first, if not found, look under /etc. And allow a special command line argument that would let a different config file to be loaded. So, say, an invocation of myprog can check for a config file in the home folder, but myprog -c /some/path/config will use /some/path/config as the file. It's also a good idea to have some default settings that you can fall back to if there is no valid config file anywhere.
The config file can go anywhere, but I'd try to put it in the same directory as any other files the program will read or write.
As for how the executable will find it, I'd pass the config file's path to the executable on the command line as an argument, with a default value of "." (which is the current directory, the one you're in when you launch the executable).
I'm developing a C++ program under Linux. I want to put some stuff (to be specific, LLVM bitcode files, but that's not important) in libraries, so I want the following directory structure:
/somewhere/bin/myBin
/somewhere/lib/myLib.bc
How do I find the lib directory? I tried to compute a relative part from argv[0], but if /somewhere is in my PATH, argv[0] will just contain myBin. Is there some way to get this path? Or do I have to set it at compile time?
How do GNU autotools deal with this? What happens exactly if I supply the --prefix option to ./configure?
Edit: The word library is a bit misleading in my case. My library consist of LLVM bitcode, so it's not an actual (shared) object file, just a file I want to open from my program. You can think of it as an image or text file.
maybe what you want is :
/usr/lib
unix directory reference: http://www.comptechdoc.org/os/linux/usersguide/linux_ugfilestruct.html
Assume your lib directory is "../lib" relative to executable
First you need to identify where myBin located, You can get it by reading /proc/self/exe
Then concat your binary file path with "../lib" will give you the lib directory.
You will have to use a compiler flag to tell the program. For example, if you have a plugin dir:
# Makefile.am
AM_CPPFLAGS = -DPLUGIN_DIR=\"${pkglibdir}\"
bin_PROGRAMS = awesome_prog
pkglib_LTLIBRARIES = someplugin.la
The list of directories to be searched is stored in the file /etc/ld.so.conf.
In Linux, the environment variable LD_LIBRARY_PATH is a colon-separated set of directories where libraries should be searched for first, before the standard set of directories; this is useful when debugging a new library or using a nonstandard library for special purposes.
LD_LIBRARY_PATH is handy for development and testing:
$ export LD_LIBRARY_PATH=/path/to/mylib.so
$ ./myprogram
[read more]
Addressing only the portion of the question "how to GNU autotools deal with this?"...
When you assign a --prefix to configure, basically two things happen: 1) it instructs the build system that everything is to be installed in ${prefix}, and 2) it looks in ${prefix}/share/config.site for any additional information about how the system is set up (it is common for that file not to exist.) It does absolutely nothing to help find libraries, but depends on the user having set up the tool chain properly. If you want to use a library in /foo/lib, you must have your toolchain set up to look there (eg, by putting /foo/lib in /etc/ld.so.conf, or by putting -L/foo/lib in LDFLAGS and "/foo/lib" in LD_LIBRARY_PATH)
The configure script relies on you to have the environment set up. It does not help you set up that environment, but does help by alerting you that you have not done so.
You could use the readlink system call on /proc/self/exe to get the path of your executable. You might then use realpath etc.
Hello now i try translate project on other platform(first platform it's windows, now company planed use Linux platform), i use eclipse in windows and Linux, language is c++. Name project PostLib and he have next structure: PostLib/common, PostLib/inc, PostLib/inc_ext, PostLib/src.
PostLib/common its part for control memory leaks and for smart pointer. PostLib/inc PostLib/inc_ext - this part for header, and PostLib/src for sources code.My problem next: In project settings, i use PostLib/common, PostLib/inc and PostLib/inc_ext, and Eclipse write error: File Def.h(PostLib/inc_ext) can not find file p_mem.h(PostLib/common). How can it be?
When i look property all direction in project i saw interesting thing: Property on directory PostLib/inc_ext difference than all project, on other directory property same like in project/ Property i mean Property->Settings->GCC C++ Compiler->Directories, i try add path (PostLib/common) , but no effect, Eclipse write error File Def.h(PostLib/inc_ext) can not find file p_mem.h(PostLib/common).
On Linux systems directory separator is /, not \!
PostLib\common\p_mem.h is a path in windows, but is not in Linux. The equivalent for Linux is PostLib/common/p_mem.h.
Also, filesystem paths on Linux are case sensitive. p_mem.h is a different file from P_Mem.h: be sure you used the right characters for files and directories.
C++ How to get a filename (and path) of the executing .so module in Unix?
Something similar to GetModuleFileName on Windows.
Although it is not a POSIX standard interface, the dladdr() function is available on many systems including Linux, Solaris, Darwin/Mac OS X, FreeBSD, HP-UX, and IRIX. This function takes an address, which could be a pointer to a static function within the module for example (if cast to void *), and fills in a Dl_info structure with information including the path name of the shared object containing that address (in the dli_fname member).
Unfortunately, there is no way to do that using UNIX or POSIX. If you need to use it to look up some sort of data, you should use the $PATH environment variable and search for the data in a path that is relative to each entry in $PATH. For example, it is not uncommon to store binaries in "installdir/bin" for some installation directory "installdir" and to store the associated data in "installdir/share/name_of_program" for some installation directory and some program named "name_of_program". If that is the case, then looking at "../share/name_of_program/name_of_resource_file" relative to each entry in getenv("PATH") is a good way of searching for resources. Another thing you could do is allow the necessary information to be provided on the commandline or in some configuration file, and only perform the search if needed as a fallback option.
Edit
Now that you've stated your rationale for this, I would advise you to simply use the QSettings class from Qt for your configuration information, as it uses the preferred native mechanism for each platform (the registry on Windows, a PLIST file on Mac OS X, the Gnome GConf database on Linux). You may want to take a look at my C++ Project Template as it uses Qt to do just this, and it provides simple commandline options to easily tweak the configuration settings ("--prefset", "--prefget", and "--preflist" manipulate QSettings).
That said, if you absolutely must use an XML configuration file of your own instead of using the preferred native mechanism, I strongly advise you to place the system-wide configuration in "installdir/etc" while placing your library in "installdir/lib" for some installation directory "installdir", as that is the typical place for configuration files on UNIX systems, and "installdir/lib" should ONLY be used for library files, not for configuration files and other errata. I suggest you place a user-specific version of the configuration file in "$XDG_CONFIG_HOME" (if it is defined) or in "$HOME/.config" (where "$HOME" is the user's home folder).
When searching for the system-wide configuration file, I would recommend that you search within $XDG_CONFIG_DIRS if it is defined; if it isn't defined, then falling back to "/etc/xdg" or searching for "../etc/name_of_your_program.conf.xml" relative to "$PATH" and possibly also relative to the "$LD_LIBRARY_PATH", "$DYLD_LIBRARY_PATH", "$DYLD_FALLBACK_LIBRARY_PATH"), the contents of "/etc/ld.so.conf" if it exists, and the contents of "/etc/ld.so.conf.d/*.conf" if those files exist, halting your search as soon as you encounter the first valid such configuration file would be a sensible approach.
Credit goes to Roger for pointing out the XDG Basedir Spec and for his excellent constructive criticisms.
Possible solutions:
You can read the /proc/{PID}/mmap file for the list of shared libraries. Where {PID} is the process pid (you can get it using getpid()).
Call the command line tool ldd for the program binary file (stored in argv[0]).
If you write a solution from scratch take a look of ldd commands source code from uClibc how to get the list of shared libs from an elf binary.