access(2) - NetBSD Manual Pages

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ACCESS(2)                 NetBSD Programmer's Manual                 ACCESS(2)

access - check access permissions of a file or pathname
Standard C Library (libc, -lc)
#include <unistd.h> int access(const char *path, int mode);
The access() function checks the accessibility of the file named by path for the access permissions indicated by mode. The value of mode is the bitwise inclusive OR of the access permissions to be checked (R_OK for read permission, W_OK for write permission and X_OK for execute/search permission) or the existence test, F_OK. All components of the pathname path are checked for access permissions (including F_OK). The real user ID is used in place of the effective user ID and the real group access list (including the real group ID) are used in place of the effective ID for verifying permission. If a process has super-user privileges and indicates success for R_OK or W_OK. the file may not actually have read or write permission bits set. If a process has super-user privileges and indicates success for X_OK, at least one of the user, group, or other execute bits is set. (However, the file may still not be executable. See execve(2).)
If path cannot be found or if any of the desired access modes would not be granted, then a -1 value is returned; otherwise a 0 value is returned.
Access to the file is denied if: [ENOTDIR] A component of the path prefix is not a directory. [ENAMETOOLONG] A component of a pathname exceeded {NAME_MAX} characters, or an entire path name exceeded {PATH_MAX} characters. [ENOENT] The named file does not exist. [ELOOP] Too many symbolic links were encountered in translating the pathname. [EROFS] Write access is requested for a file on a read-only file system. [ETXTBSY] Write access is requested for a pure procedure (shared text) file presently being executed. [EACCES] Permission bits of the file mode do not permit the request- ed access, or search permission is denied on a component of the path prefix. The owner of a file has permission checked with respect to the ``owner'' read, write, and exe- cute mode bits, members of the file's group other than the owner have permission checked with respect to the ``group'' mode bits, and all others have permissions checked with re- spect to the ``other'' mode bits. [EFAULT] path points outside the process's allocated address space. [EIO] An I/O error occurred while reading from or writing to the file system.
chmod(2), execve(2), stat(2)
The access() function conforms to IEEE Std 1003.1-1990 (``POSIX'').
access() is a potential security hole and should never be used. NetBSD 1.6.2 April 1, 1994 2
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