CHMOD

Section: System Calls (2)
Updated: August 1, 1992
Index Return to Main Contents
 

NAME

chmod - change mode of file  

SYNOPSIS

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

DESCRIPTION

The chmod function changes the mode of the file whose pathname is given by path according to the value of mode. The fchmod function changes the mode of the open file given by file descriptor fd. Only a process whose effective user ID matches the file owner or is that of the super-user can change the mode of a file. The mode argument is a bitwise inclusive OR combination of the values described in stat(2) or stat(2P). Writing to a file always turns off the set-user-id and set-group-id bits.

If an executable file is set up for sharing (this is the default) then mode S_ISVTX (the `sticky bit') prevents the system from abandoning the swap-space image of the program-text portion of the file when its last user terminates. Ability to set this bit on executable files is restricted to the super-user.

If mode S_ISVTX (the `sticky bit') is set on a directory, an unprivileged user may not delete or rename files of other users in that directory. For more details of the properties of the sticky bit, see sticky(8).

Upon successful completion, chmod marks for update the st_ctime field of the file.  

RETURN VALUE

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

ERRORS

If any of the following conditions occurs, chmod returns -1 and sets errno to the corresponding value:
[EACCES]
Search permission is denied for a component of the path prefix.
[EFAULT]
The path argument points outside the process's allocated address space.
[EINVAL]
The pathname contains a character with the high-order bit set.
[EIO]
An I/O error occurred while reading from or writing to the file system.
[ELOOP]
Too many symbolic links were encountered in translating the pathname.
[ENAMETOOLONG]
A component of path exceeds 255 characters, or the entire pathname exceeds 1023 characters. For POSIX applications these values are given by the constants {NAME_MAX} and {PATH_MAX}, respectively.
[ENOTDIR]
A component of the path prefix is not a directory.
[ENOENT]
The named file does not exist or path points to an empty string.
[EPERM]
The effective user ID does not match the owner of the file and the effective user ID is not the super-user.
[EROFS]
The named file resides on a read-only file system.

The following errors cause Fchmod to fail and return -1:

[EBADF]
The descriptor is not valid.
[EINVAL]
Fd refers to a socket, not to a file.
[EIO]
An I/O error occurred while reading from or writing to the file system.
[EROFS]
The file resides on a read-only file system.
 

SEE ALSO

chmod(1), chown(2), mkdir(2), mkfifo(2P), open(2), stat(2) or stat(2P), sticky(8)

 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
SEE ALSO
This document was created by man2html, using the manual pages.
Time: 00:59:11 GMT, September 26, 2024