./_Man_Solaris_2.6_html/html2/chmod.2.html

Manual page for chmod(2)

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

chmod() and fchmod() 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 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 execution) is cleared.

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

Upon successful completion, a value of 0 is returned. Otherwise, a value of -1 is returned and errno is set to indicate the error.

ERRORS

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 component of the path prefix of path.
EFAULT: path 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.
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 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: fildes 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 and is not super-user.
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() function.
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.

ATTRIBUTES

See attributes.5 for descriptions of the following attributes: