'fopen' returns NULL - "no such file or directory"

Question

I've written a super simple C command line tool that's supposed to read a file out from the path specified in argv[1]. I'm debugging using Xcode on OS X, so the working directory at the time of running is an Xcode-created directory separate from the file I want to read. (Xcode plugs in the arguments automatically, so that's not the problem.) I suspect the problem is related to my not understanding how fopen works. When I put in a path name, is it relative to the working directory? Will it work if I use the absolute path?

I've checked this post, this one, and this one, but they don't seem to help me in this case.

Here's the code I'm using - it's in the main function:

for (int i = 0; i < argc; i++)
    printf("arg%i: %s\n", i, argv[i]);

if (argc > 1)
{
    //Open the file specified by the first argument
    system("pwd");
    FILE *file = fopen(argv[1], "r");    //Always returns NULL

    if (file)
        //This isn't ever reached
    else
        printf("%s\n", strerror(errno));        
}

The output looks like this:

arg0: /Users/home/Library/Developer/Xcode/DerivedData/VSSequenceAlignment-avlfehlrtqiybygqfgueezoysnyi/Build/Products/Debug/VSSequenceAlignment
arg1: C:/Users/venkateshsivaramanDP/Documents/test/testdoc.txt
/Users/venkateshsivaramanDP/Library/Developer/Xcode/DerivedData/VSSequenceAlignment-avlfehlrtqiybygqfgueezoysnyi/Build/Products/Debug
No such file or directory

After changing the arg1 to use forward slashes it hasn't changed the error. Admittedly it's a step closer to the actual problem.

`argv[0]` seems to be an OSX-style path, whereas `argv[1]` seems to be a Windows-style path; what's up with that? — Oliver Charlesworth, Sep 20 '13 at 21:50
I saw that some people were using the backslashes on one of the SO posts I linked, I think. It didn't seem to me like there was a difference until you said so. — architectpianist, Sep 20 '13 at 21:59

score 1 · Accepted Answer · edited Feb 18 '15 at 19:42

1

Your path is wrong; you are using a Windows path.

Compare your supplied path to arg0, specifying the path to the executable. arg1 has to be in the same style.

edited Feb 18 '15 at 19:42

Peter Mortensen

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answered Sep 20 '13 at 21:51

Femaref

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If you mean the backslashes, changing them around didn't help either way. I still get the same error. – architectpianist Sep 20 '13 at 21:54
unix paths don't start with `C:`. go to the file you want to open in terminal and execute `echo $(pwd)/file_you_want_to_open`. This is the path you need to provide. – Femaref Sep 20 '13 at 21:57
There we go! Thank you, it turned out to be the C: causing the problem. If you want to add that to your answer, I'll go ahead and accept it. Because I may need to use an external disk to store the file I want to read in the future, how would I go about supplying that path? – architectpianist Sep 20 '13 at 22:02
That's entirely depending on the OS. in OSX, such volumes are in `/Volumes/`, while in others, like ubuntu or debian, it usually is in `/mnt/`. – Femaref Sep 20 '13 at 22:11

score 0 · Answer 2 · edited Feb 18 '15 at 19:43

0

Yes, absolute paths work with fopen, but that's not your problem. I think that your problem comes from the content of arg[1], and I think it contains C:\Users\home\Documents\test\testdoc.txt which is a Windows path and you're on OS X.

edited Feb 18 '15 at 19:43

Peter Mortensen

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answered Sep 20 '13 at 21:54

Farouq Jouti

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'fopen' returns NULL - "no such file or directory"

2 Answers2