I feel like this must be very easy, but I can't find the answer anywhere. In octave (and probably matlab but I haven't verified), you can source the contents of a file by doing
source /path/to/filename
However, let's say I have the filename stored in a variable called file. If you do source file, it treats file as the path rather than what is stored in file. I have tried inserting eval in various places but if that is the answer, I haven't found the correct invocation. I don't know much octave; there is surely a trivial answer to this that I am overlooking?
Not sure about octave, but try to use a function call
source(fname)
That's what you do in matlab at least.
Related
In short: I am trying to load a csv file but the program always overwrites the existing file as an empty new file.
Longer: I am pretty new to Fortran, so bear with me. I am trying to read data from a csv file into a fortran program. Now I didn't write the program and it is pretty big, so I can't post the whole thing here. The program consists of a whole bunch of .f90 files and everything is compiled using a makefile. Now since I am loading the gcc module before compiling, I am assuming that it is compiled using GNU Fortran, because it is part of gcc. (idk how to find out if that is correct)
The compiler returns an executable in a different directory. When I execute the program in that directory it apparently overwrites the existing .csv file with a new blank one, so the program only reads "End of File". I don't know why it always creates a new file, how do I stop it from doing so?
As a side note, the csv file I am trying to read simply consists of a single column of floats, e.g.
"0.01, 0.13, 0.041,..." etc.
The code that I inserted into a subroutine of one of the .f90 files is the following:
real*8, dimension(nz) :: Nsq
integer :: i
open(10, file='Nsq.csv')
do i=1,20
read(10, *) Nsq(i)
enddo
close(10)
I have also tried to write a small test program, essentially running the same code as above. That one works just fine and outputs the contents of the csv file without any issues. For that one I use gfortran to compile it.
I have no experience in Fortran at all, so I am completely stumped, why this happens. I know the chances are slim that you guys can help me with this, since I can't provide the whole source code. But maybe someone has an idea why this occurs. Maybe you know an alternate way of reading csv files?
Thanks for your time.
The open-statement in Fortran OPEN(connect-spec-list), has a lot of connection specifications which define how an external file should be managed (see. Fortran 2018 Standard sec 12.5.6).
When you open a file using the simplest form of the open-statement:
OPEN(unit=unitid,file="filename")
A lot of default assumptions are made such as: ACCESS="SEQUENTIAL", ASYNCHRONOUS="NO", BLANK="NULL", .... The most important ones, however, are ACTION and STATUS which define the purpose of the file. The action specification states if you want to use the file for reading, writing or both, while the status essentially defines if we work on an existing file or not, and what we should do with it (replace it, keep it, ...)
Both these specifications have a default compiler dependent state.
In the Intel compiler suit, the default is action="readwrite", status="unknown" (see here and here)
Intel defines the status="unknown" as :Indicates the file may or may not exist. If the file does not exist, a new file is created and its status changes to 'OLD'.
The Gnu compiler suit has a different take on this. The default action is defined by a set of rules which depend on its accessibility if the file exists (+rw,+r-w,-r+w) (see here). The behaviour for the default action="unknown" is not documented but seems to be REWRITE (see Default Status of "Unknown" in Open)
It is advised to use a proper method if you know what you want to do with the file:
OPEN(newunit=unitid, file="filename", action="read", status="old")
I have a folder for Octave M-files in C:\\Users\Dropbox\Octave, under which are various subfolders by function categories (normal distribution, chisq...). I just started making those subfolders and they will keep changing (adding, removing, reshuffling) as time goes on.
I would just like to set that folder as root and have Octave search for functions recursively there, just like you set a classpath in Java and JVM searches all folders there.
I used addpath(genpath('C:\\Users\Dropbox\Octave')), but the paths generated are then fixed, not reflecting subsequent subfolder changes.
Shall I add addpath(genpath('C:\\Users\Dropbox\Octave')) to the .octaverc file?
I think there is some confusion here. There are several ways to interact with the path, but for the most part these do not result in permanent changes, unless you save this somehow.
Simply adding a path for an existing octave session will not result in any permanent changes to the usual path that octave initialises at startup. Therefore when you say:
I used addpath(genpath('C:\Users\Dropbox\Octave')), but the paths generated are then fixed, not reflecting subsequent subfolder changes.
this makes no sense, because as soon as you exit your octave session, those added paths should have been gone altogether, and not appear in later octave sessions.
It is more likely that at some point you added these paths, and then used the savepath command, which resulted in your custom paths being added to your .octaverc file.
If that is the case, then yes, you can expect that octave will not "update" what was written in your .octaverc file, unless you call savepath again with an updated path definition.
If you would like the addpath(genpath('C:\Users\Dropbox\Octave')) command you mentioned to be called every time octave starts, so that the current/updated directory structure is loaded, then yes, the best way to do it would be to add that command to your .octaverc file. Make sure you remove the lines in your .octaverc that refer to the previous changes made by savepath. Note that there may be several levels of octaverc files that you need to check (see the relevant page in the manual)
Alternatively, you could simply make sure that this line appears in every script you want to call which intends to make use of those files.
While you may consider this last approach tedious, programmatically it is the most recommended one, since it makes dependencies clear in your code. This is especially important if you ever plan to share your code (and doubly so if you'd like it to be matlab compatible).
PS. All the above mostly applies to matlab too, with the exception that a) matlab's savepath saves path information in a file called pathdef.m, rather than directly in your startup files, and b) matlab uses startup.m instead of .octaverc as startup files. Also, if you don't care about doing this programmatically, matlab provides pathtool, which is a graphical interface for adding / saving directories to the matlab path.
I have both JSON file and JL file on my computer but when I open them in Notepad their structure looks like the same. What is the difference between them? where shall I use each one?
Actually, the time that I was asking this question I didn't know that "the file type is no guarantee of what is inside it". in other words I thought that for every file name there is a separate manifesto and if a files name is ".something", there is a unique manifesto for it. But now I know that I can create a file, write anything that I want into it and name it ".peyman" and yes there is nothing special with it!
What was that file? the file was JSON Lines file format.
Where did I find it? in the Scrapy except writing scrapy crawl name -o file.json I saw that somebody wrote scrapy crawl name -o file.jl. I tried that and the file was 99% like JSON file so I wondered and asked this question here.
So:
What is the difference between a .JSON file and .JL file? Now I know that the better question is "What is the difference between a .JSON file and .JL file in the Scrapy?"
The JSON Line is like JSON but without the "[" and "]" at the
beginning and the end. it is used in the Scrapy because of this
There's quite a few things that a jl file extension could be referring to. If I remember correctly, it originally had something to do with the window manager Sawfish.
Sawfish was developed in Lisp, and the jl file was a Lisp source file for Sawfish. However, I'm guessing (because you said that inside was JSON-like sauce) that's not what you're asking about.
In that case, I do recall a few projects on GitHub... JSON lambda and Julia.
Both of those may be the reason why you're seeing JSON in a jl file. Without more information on where you got that file, or what it was part of, though, we won't be able to help you much.
That said, file extensions rarely matter in terms of Linux. In Windows, they're far more important, but in Linux you could literally append anything to a file as an "extension" (ie. thisfile.whatever) and you could still open it up in an editor. The same is true for most editors in Windows.
Likely, the packager of that file decided on jl for their own reasons, rather than following convention of using .json.
I guess JL extension is used for many purposes, but JL is also one of the few extensions used for JSON-lines (also known as NDJSON or JSONL).
This format can contain multiple JSON values, one JSON value (with "compact" formatting) per line and is useful for e.g. streaming or logging.
I'm currently looking for a way to add data to an already compiled ELF executable, i.e. embedding a file into the executable without recompiling it.
I could easily do that by using cat myexe mydata > myexe_with_mydata, but I couldn't access the data from the executable because I don't know the size of the original executable.
Does anyone have an idea of how I could implement this ? I thought of adding a section to the executable or using a special marker (0xBADBEEFC0FFEE for example) to detect the beginning of the data in the executable, but I do not know if there is a more beautiful way to do it.
Thanks in advance.
You could add the file to the elf file as a special section with objcopy(1):
objcopy --add-section sname=file oldelf newelf
will add the file to oldelf and write the results to newelf (oldelf won't be modified)
You can then use libbfd to read the elf file and extract the section by name, or just roll your own code that reads the section table and finds you section. Make sure to use a section name that doesn't collide with anything the system is expecting -- as long as your name doesn't start with a ., you should be fine.
I've created a small library called elfdataembed which provides a simple interface for extracting/referencing sections embedded using objcopy. This allows you to pass the offset/size to another tool, or reference it directly from the runtime using file descriptors. Hopefully this will help someone in the future.
It's worth mentioning this approach is more efficient than compiling to a symbol, as it allows external tools to reference the data without needing to be extracted, and it also doesn't require the entire binary to be loaded into memory in order to extract/reference it.
How can I put multiple functions in one file and later get access to all of them in the octave interpreter ? I don't want to have a thousand files and want to group functions together. I'd like something like 'import' in python.
Once you have saved all your function definitions in a single script file, use source("filename") to have access to these functions within the interpreter.
What you're looking for is called “script files”, defined there: http://www.gnu.org/software/octave/doc/interpreter/Script-Files.html