CHMOD(2-SVR4) RISC/os Reference Manual CHMOD(2-SVR4)
NAME
chmod, fchmod - change mode of file
SYNOPSIS
#include <sys/types.h>
#include <sys/stat.h>
int chmod(const char *path, modet mode);
int fchmod(int fildes, modet mode);
DESCRIPTION
chmod and fchmod set the access permission portion of the
mode of the file whose name is given by path or referenced
by the descriptor fildes to the bit pattern contained in
mode. Access permission bits are interpreted as follows:
S_ISUID 04000 Set user ID on execution.
S_ISGID 020#0 Set group ID
on execution if # is 7, 5, 3, or 1
Enable mandatory file/record
locking if # is 6, 4, 2, or 0
S_ISVTX 01000 Save text image after execution.
S_IRWXU 00700 Read, write, execute by owner.
S_IRUSR 00400 Read by owner.
S_IWUSR 00200 Write by owner.
S_IXUSR 00100 Execute (search if a directory) by owner.
S_IRWXG 00070 Read, write, execute by group.
S_IRGRP 00040 Read by group.
S_IWGRP 00020 Write by group.
S_IXGRP 00010 Execute by group.
S_IRWXO 00007 Read, write, execute (search) by others.
S_IROTH 00004 Read by others.
S_IWOTH 00002 Write by others
S_IXOTH 00001 Execute by others.
Modes are constructed by OR'ing the access permission bits.
The effective user ID of the process must match the owner of
the file or the process must have the appropriate privilege
to change the mode of a file.
If the process is not a privileged process and the file is
not a directory, mode bit 01000 (save text image on execu-
tion) is cleared.
If neither the process nor a member of the supplementary
group list is privileged, and the effective group ID of the
process does not match the group ID of the file, mode bit
02000 (set group ID on execution) is cleared.
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If a 0410 executable file has the sticky bit (mode bit
01000) set, the operating system will not delete the program
text from the swap area when the last user process ter-
minates. If a 0413 or ELF executable file has the sticky
bit set, the operating system will not delete the program
text from memory when the last user process terminates. In
either case, if the sticky bit is set the text will already
be available (either in a swap area or in memory) when the
next user of the file executes it, thus making execution
faster.
If a directory is writable and has the sticky bit set, files
within that directory can be removed or renamed only if one
or more of the following is true [see unlink(2) and
rename(2)]:
the user owns the file
the user owns the directory
the file is writable by the user
the user is a privileged user
If the mode bit 02000 (set-group-ID-on-execution) is set and
the mode bit 00010 (execute or search by group) is not set,
mandatory file/record locking will exist on a regular file.
This may affect future calls to open(2), creat(2), read(2),
and write(2) on this file.
If the set-group-ID bit is set on a directory, BSD group
ownership semantics on file creation are used but are
applied on a case-by-case basis instead of system-wide.
(See the description of riscos_group_parent in kopt(8-BSD)).
Upon successful completion, chmod and fchmod mark for update
the st_ctime field of the file.
chmod will fail and the file mode will be unchanged if one
or more of the following are true:
EACCES Search permission is denied on a com-
ponent of the path prefix of path.
EFAULT path points outside the allocated
address space of the process.
EINTR A signal was caught during execution of
the system call.
EIO An I/O error occurred while reading from
or writing to the file system.
ELOOP Too many symbolic links were encountered
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CHMOD(2-SVR4) RISC/os Reference Manual CHMOD(2-SVR4)
in translating path.
EMULTIHOP Components of path require hopping to
multiple remote machines and file system
type does not allow it.
ENAMETOOLONG The length of the path argument exceeds
{PATH_MAX}, or the length of a path com-
ponent exceeds {NAME_MAX} while
_POSIX_NO_TRUNC is in effect.
ENOTDIR A component of the prefix of path is not
a directory.
ENOENT Either a component of the path prefix,
or the file referred to by path does not
exist or is a null pathname.
ENOLINK fildes points to a remote machine and
the link to that machine is no longer
active.
EPERM The effective user ID does not match the
owner of the file and the process does
not have appropriate privilege.
EROFS The file referred to by path resides on
a read-only file system.
fchmod will fail and the file mode will be unchanged if:
EBADF fildes is not an open file descriptor
EIO An I/O error occurred while reading from
or writing to the file system.
EINTR A signal was caught during execution of
the fchmod system call.
ENOLINK path points to a remote machine and the
link to that machine is no longer
active.
EPERM The effective user ID does not match the
owner of the file and the process does
not have appropriate privilege.
EROFS The file referred to by fildes resides
on a read-only file system.
SEE ALSO
chown(2), creat(2), fcntl(2), mknod(2), open(2), read(2),
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CHMOD(2-SVR4) RISC/os Reference Manual CHMOD(2-SVR4)
stat(2), write(2), mkfifo(3C), stat(5).
chmod(1) in the User's Reference Manual.
DIAGNOSTICS
Upon successful completion, a value of 0 is returned. Oth-
erwise, a value of -1 is returned and errno is set to indi-
cate the error.
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