access(2) [opendarwin 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 mode); DESCRIPTION
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 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; otherwise a 0 value is returned. ERRORS
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 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. [EINVAL] An invalid value was specified for mode. 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
Check Out this Related Man Page
access(2) System Calls access(2) NAME
access - determine accessibility of a file SYNOPSIS
#include <unistd.h> int access(const char *path, int amode); DESCRIPTION
The access() function checks the file named by the pathname pointed to by the path argument for accessibility according to the bit pattern contained in amode, using the real user ID in place of the effective user ID and the real group ID in place of the effective group ID. This allows a setuid process to verify that the user running it would have had permission to access this file. The value of amode is either the bitwise inclusive OR of the access permissions to be checked (R_OK, W_OK, X_OK) or the existence test, F_OK. These constants are defined in <unistd.h> as follows: R_OK Test for read permission. W_OK Test for write permission. X_OK Test for execute or search permission. F_OK Check existence of file See intro(2) for additional information about "File Access Permission". If any access permissions are to be checked, each will be checked individually, as described in intro(2). If the process has appropriate privileges, an implementation may indicate success for X_OK even if none of the execute file permission bits are set. RETURN VALUES
If the requested access is permitted, access() succeeds and returns 0. Otherwise, -1 is returned and errno is set to indicate the error. ERRORS
The access() function will fail 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. EFAULT path points to an illegal address. EINTR A signal was caught during the access() function. ELOOP Too many symbolic links were encountered in resolving path. ELOOP A loop exists in symbolic links encountered during resolution of the path argument. ENAMETOOLONG The length of the path argument exceeds {PATH_MAX}, or a pathname component is longer than {NAME_MAX} while _POSIX_NO_TRUNC is in effect. ENOENT A component of path does not name an existing file or path is an empty string. ENOLINK path points to a remote machine and the link to that machine is no longer active. 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. The access() function may fail if: EINVAL The value of the amode argument is invalid. ENAMETOOLONG Pathname resolution of a symbolic link produced an intermediate result whose length exceeds {PATH_MAX}. ETXTBSY Write access is requested for a pure procedure (shared text) file that is being executed. USAGE
Additional values of amode other than the set defined in the description might be valid, for example, if a system has extended access con- trols. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ |MT-Level |Async-Signal-Safe | +-----------------------------+-----------------------------+ SEE ALSO
intro(2), chmod(2), stat(2), attributes(5), standards(5) SunOS 5.10 23 Apr 2002 access(2)