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ACCESS(2) BSD System Calls Manual ACCESS(2) NAME access -- check access permissions of a file or pathname LIBRARY Standard C Library (libc, -lc) 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 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. Even if a process has appropriate privileges and indicates success for X_OK, the file may not actually have execute permission bits set. Like- wise 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 255 characters, or an entire path name exceeded 1023 characters. [ENOENT] The named file does not exist. [ELOOP] Too many symbolic links were encountered in translat- ing 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 re- quested 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 oth- ers 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) STANDARDS The access() function call is expected to conform to ISO/IEC 9945-1:1990 ("POSIX.1"). CAVEAT Access() is a potential security hole due to race conditions and should never be used. Setuid and setgid applications should restore the effec- tive uid or gid and perform actions directly rather than use access() to simulate access checks for the real user of group id. HISTORY An access() function call appeared in Version 7 AT&T UNIX. BSD April 1, 1994 BSD
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | STANDARDS | CAVEAT | HISTORY
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