Advanced UNIX Programming

Testing Access to a File

Sometimes it is necessary to test the access of a file system object prior to its actual use. For example, if your application must provide the pathname of an executable to another application, you might want to make sure that you possess execute rights on that file. Testing access ahead of time may be simpler for corrective action. This is accomplished with the UNIX function access(2):

#include <unistd.h>

int access(const char *path, int mode);

mode:

F_OK, R_OK, W_OK and/or X_OK

The pathname of the object to be tested for access is provided in the first argument. The mode argument contains the bit-wise OR of the following values:

File exists	F_OK
Read access	R_OK
Write access	W_OK
Execute access	X_OK

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