CHMOD

Section: Linux Programmer's Manual (2)
Updated: 21 July 1993
Index Return to Main Contents
 

NAME

chmod, fchmod - change permissions of a 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 mode of the file given by path or referenced by filedes is changed.

Modes are specified by or'ing the following:

S_ISUID
04000 set user ID on execution
S_ISGID
02000 set group ID on execution
S_ISVTX
01000 sticky bit
S_IRUSR (S_IREAD)
00400 read by owner
S_IWUSR (S_IWRITE)
00200 write by owner
S_IXUSR (S_IEXEC)
00100 execute/search by owner
S_IRGRP
00040 read by group
S_IWGRP
00020 write by group
S_IXGRP
00010 execute/search by group
S_IROTH
00004 read by others
S_IWOTH
00002 write by others
S_IXOTH
00001 execute/search by others

The effective UID of the process must be zero or must match the owner of the file.

The effective UID or GID must be appropriate for setting execution bits.

Depending on the file system, set user ID and set group ID execution bits may be turned off if a file is written. On some file systems, only the super-user can set the sticky bit, which may have a special meaning (i.e., for directories, a file can only be deleted by the owner or the super-user).

 

RETURN VALUE

On success, zero is returned. On error, -1 is returned, and errno is set appropriately.  

ERRORS

Depending on the file system, other errors can be returned. The more general errors for chmod are listed below:

EPERM
The effective UID does not match the owner of the file, and is not zero.
EROFS
The named file resides on a read-only file system.
EFAULT
path points outside your accessible address space.
ENAMETOOLONG
path is too long.
ENOENT
The file does not exist.
ENOMEM
Insufficient kernel memory was available.
ENOTDIR
A component of the path prefix is not a directory.
EACCES
Search permission is denied on a component of the path prefix.
ELOOP
path contains a circular reference (i.e., via a symbolic link)

The general errors for fchmod are listed below:

EBADF
The descriptor is not value.
ENOENT
See above.
EPERM
See above.
EROFS
See above.
 

SEE ALSO

open(2), chown(2), stat(2)


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
SEE ALSO

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