fchmod(2)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | ATTRIBUTES | SUMMARY OF TRUSTED SOLARIS CHANGES | SEE ALSO | NOTES

NAME

chmod, fchmod– change access permission mode of file

SYNOPSIS

#include <sys/types.h>
#include <sys/stat.h>

int chmod(const char *path, mode_t mode);
int fchmod(int fildes, mode_t mode);

DESCRIPTION

The chmod() and fchmod() functions set the access permission portion of the mode of the file whose name is given by path or referenced by the open file 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 the bitwise OR operation of the access permission bits.

The effective user ID of the process must match the owner of the file or the process must have the PRIV_FILE_SETDAC 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 execution) is cleared. The calling process may assert the PRIV_SYS_CONFIG privilege to override this restriction.

If neither the process is privileged, nor the file's group is a member of the process's supplementary group list, 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.

If a directory is writable and has S_ISVTX (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 a directory has the set group ID bit set, a given file created within that directory will have the same group ID as the directory, if that group ID is part of the group ID set of the process that created the file. Otherwise, the newly created file's group ID will be set to the effective group ID of the creating process.

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.

Upon successful completion, chmod() and fchmod() mark for update the st_ctime field of the file.

RETURN VALUES

chmod() returns:

0

On success.

-1

On failure, and sets errno to indicate the error.

ERRORS

The chmod() function will fail if:

EACCES

Search permission is denied on a component of the path prefix of path. To override this restriction, the calling process may assert the PRIV_FILE_DAC_SEARCH privilege and/or the PRIV_FILE_MAC_SEARCH privilege.

The calling process does not own the final object specified in path or does not own fildes. To override this restriction, the calling process may assert the PRIV_FILE_SETDAC privilege.

Write permission is denied on path or fildes. To override this restriction, the calling process may assert the PRIV_FILE_DAC_WRITE and/or the PRIV_FILE_MAC_WRITE privilege.

EFAULT

The path argument points to an illegal address.

EINTR

A signal was caught during execution of the function.

EIO

An I/O error occurred while reading from or writing to the file system.

ELOOP

Too many symbolic links were encountered in translating path.

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

Either a component of the path prefix or the file referred to by path does not exist or is a null pathname.

ENOLINK

The fildes argument points to a remote machine and the link to that machine is no longer active.

ENOTDIR

A component of the prefix of path is not a directory.

EPERM

The effective user ID does not match the owner of the file. To override this restriction, the calling process may assert the PRIV_FILE_SETDAC privilege.

EROFS

The file referred to by path resides on a read-only file system.

The fchmod() function will fail if:

EBADF

The fildes argument 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() function.

ENOLINK

The path argument points to a remote machine and the link to that machine is no longer active.

EROFS

The file referred to by fildes resides on a read-only file system.

ATTRIBUTES

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPE	ATTRIBUTE VALUE
MT-Level	chmod() is Async-Signal-Safe

SUMMARY OF TRUSTED SOLARIS CHANGES

Appropriate privilege is required to override access checks.

• To override a search permission error, the calling process requires the PRIV_FILE_MAC_SEARCH privilege.

• To override a write permission error, the calling process requires the PRIV_FILE_DAC_WRITE and/or the PRIV_FILE_MAC_WRITE privilege.

• If the calling process does not own the object, the calling process requires the PRIV_FILE_SETDAC privilege.

To set the sticky bit on a file, the calling process may assert the PRIV_SYS_CONFIG privilege.

To set the set-user-ID on a user who is not the effective user ID of the calling process, the calling process may assert the PRIV_FILE_SETID privilege.

To set the set-group-ID bit on a group not in effective or supplementary group IDs of the calling process, the calling process may assert the PRIV_FILE_SETID privilege.

SEE ALSO

Trusted Solaris 8 HW 12/02 Reference Manual

chmod(1), chown(2), creat(2), fcntl(2), mknod(2), open(2), read(2), rename(2), stat(2), write(2)

SunOS 5.8 Reference Manual

mkfifo(3C), stat(3HEAD), attributes(5)

System Interface Guide

NOTES

If you use chmod() to change the file group owner permissions on a file with ACL entries, both the file group owner permissions and the ACL mask are changed to the new permissions. Be aware that the new ACL mask permissions may change the effective permissions for additional users and groups who have ACL entries on the file.

Trusted Solaris 8 HW 12/02  Last Revised 3 Aug 2001

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | ATTRIBUTES | SUMMARY OF TRUSTED SOLARIS CHANGES | SEE ALSO | NOTES