Pass a string as a char pointer array using ctypes

Question

I have a C function of this signature:

int fileopen(const char *fname, int flags)

In Linux system, I want to pass the fname from Python using ctypes so I use ctypes.c_char_p("file1.dat") as the following:

import ctypes as ctypes

dll_name = "IO/pyaio.so"
dllabspath = os.path.dirname(os.path.abspath(__file__)) + os.path.sep + dll_name
pyaio = ctypes.CDLL(dllabspath)

fd_w = pyaio.fileopen(ctypes.c_char_p("file1.dat"), 1)

But I get this error:

Traceback (most recent call last):
  File "test.py", line 21, in <module>
    fd_w = pyaio.fileopen(ctypes.c_char_p("file1.dat"), 1) # 0 read, 1 write
TypeError: bytes or integer address expected instead of str instance

I don't know another way to pass the string"file1.dat" than using ctypes.c_char_p. How to solve this problem?

Thank you

fferri · Accepted Answer · 2018-04-22 22:58:56Z

5

Change "file1.dat" to b"file1.dat" (which is the same you would get with 'file1.dat'.encode('ascii')).

answered Apr 22, 2018 at 22:58

fferri

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1 Comment

steve Over a year ago

Brilliant. Thank you very much

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