access(2) [minix man page]
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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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. ENXIO The path argument points to a character or block device special file and the corresponding device has been retired by the fault management framework. 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 |Committed | +-----------------------------+-----------------------------+ |MT-Level |Async-Signal-Safe | +-----------------------------+-----------------------------+ |Standard |See standards(5). | +-----------------------------+-----------------------------+ SEE ALSO
Intro(2), chmod(2), stat(2), attributes(5), standards(5) SunOS 5.11 8 Jul 2007 access(2)