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access(2) [osx man page]

ACCESS(2)						      BSD System Calls Manual							 ACCESS(2)

NAME
access -- check access permissions of a file or pathname SYNOPSIS
#include <unistd.h> int access(const char *path, int amode); DESCRIPTION
The access() function checks the accessibility of the file named by path for the access permissions indicated by amode. The value of amode 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 exe- cute/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. Even if a process has appropriate privileges and indicates success for X_OK, the file may not actually have execute permission bits set. Likewise for R_OK and W_OK. RETURN VALUES
If path cannot be found or if any of the desired access modes would not be granted, then a -1 value is returned and the global integer vari- able errno is set to indicate the error. Otherwise, a 0 value is returned. ERRORS
Access to the file is denied if: [EACCES] Permission bits of the file mode do not permit the requested 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 execute 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 respect to the ``other'' mode bits. [EFAULT] Path points outside the process's allocated address space. [EINVAL] An invalid value was specified for amode. [EIO] An I/O error occurred while reading from or writing to the file system. [ELOOP] Too many symbolic links were encountered in translating the pathname. [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. [ENOTDIR] A component of the path prefix is not a directory. [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 that is presently being executed. SEE ALSO
chmod(2), stat(2) STANDARDS
The access() function conforms to ISO/IEC 9945-1:1990 (``POSIX.1''). CAVEAT
Access() is a potential security hole and should never be used. 4th Berkeley Distribution April 1, 1994 4th Berkeley Distribution

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ACCESS(2)							System Calls Manual							 ACCESS(2)

NAME
access - determine accessibility of file SYNOPSIS
#include <sys/types.h> #include <unistd.h> #define R_OK 4/* test for read permission */ #define W_OK 2/* test for write permission */ #define X_OK 1/* test for execute (search) permission */ #define F_OK 0/* test for presence of file */ int access(const char *path, mode_t mode) DESCRIPTION
Access checks the given file path for accessibility according to mode, which is an inclusive or of the bits R_OK, W_OK and X_OK. Specify- ing mode as F_OK (i.e., 0) tests whether the directories leading to the file can be searched and the file exists. The real user ID and the group access list (including the real group ID) are used in verifying permission, so this call is useful to set- UID programs. Notice that only access bits are checked. A directory may be indicated as writable by access, but an attempt to open it for writing will fail (although files may be created there); a file may look executable, but execve will fail unless it is in proper format. RETURN VALUE
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. ERRORS
Access to the file is denied if one or more of the following are true: [ENOTDIR] A component of the path prefix is not a directory. [ENAMETOOLONG] The path name exceeds PATH_MAX characters. [ENOENT] The named file does not exist. [EACCES] Search permission is denied for a component of the path prefix. [ELOOP] Too many symbolic links were encountered in translating the pathname. (Minix-vmd) [EROFS] Write access is requested for a file on a read-only file system. [EACCES] Permission bits of the file mode do not permit the requested 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 execute 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 respect 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. SEE ALSO
chmod(2), stat(2). 4th Berkeley Distribution May 22, 1986 ACCESS(2)

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