access(2) manual page
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access - determine accessibility of a file
#include <unistd.h>
int access(const char *path, int amode);
Async-Signal-Safe
access() checks the file pointed to by path 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 bit pattern contained
in amode is constructed by an OR of the access permissions to be checked
(R_OK
, W_OK
, and 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 the requested access is permitted,
a value of 0 is returned. Otherwise, a value of -1 is returned and errno
is set to indicate the error.
Access to the file is denied if one
or more of the following are true:
- EACCES
- Search permission is denied
on a component of the path prefix.
- EACCES
- Permission bits of the file mode
do not permit the requested access.
- EFAULT
- path points to an illegal address.
- EINTR
- A signal was caught during the access() function.
- ELOOP
- Too many
symbolic links were encountered in translating path.
- EMULTIHOP
- Components
of path require hopping to multiple remote machines.
- ENAMETOOLONG
- The length
of the path argument exceeds {PATH_MAX}, or the length of a path component
exceeds {NAME_MAX} while {_POSIX_NO_TRUNC} is in effect.
- ENOENT
- The path
argument points to an empty string or to the name of a file that does not
exist.
- 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is no longer active.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.
intro(2)
,
chmod(2)
, stat(2)
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