chmod(2) [minix man page]
CHMOD(2) System Calls Manual CHMOD(2) NAME
chmod - change mode of file SYNOPSIS
#include <sys/types.h> #include <sys/stat.h> int chmod(const char *path, mode_t mode) DESCRIPTION
The file whose name is given by path has its mode changed to mode. Modes are constructed by or'ing together some combination of the fol- lowing, defined in <sys/stat.h>: S_ISUID 04000 set user ID on execution S_ISGID 02000 set group ID on execution S_ISVTX 01000 `sticky bit' (see below) 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 on 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 (search on directory) by group S_IRWXO 00007 read, write, execute by others S_IROTH 00004 read by others S_IWOTH 00002 write by others S_IXOTH 00001 execute (search on directory) by others If mode ISVTX (the `sticky bit') is set on a directory, an unprivileged user may not delete or rename files of other users in that direc- tory. (Minix-vmd) Only the owner of a file (or the super-user) may change the mode. Writing or changing the owner of a file turns off the set-user-id and set-group-id bits unless the user is the super-user. This makes the system somewhat more secure by protecting set-user-id (set-group-id) files from remaining set-user-id (set-group-id) if they are modified, at the expense of a degree of compatibility. RETURN VALUE
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: [ENOTDIR] A component of the path prefix is not a directory. [ENAMETOOLONG] The path name exceeds PATH_MAX characters. [ENOENT] The named file does not exist. [EACCES] Search permission is denied for a component of the path prefix. [ELOOP] Too many symbolic links were encountered in translating the pathname. (Minix-vmd) [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. [EFAULT] Path points outside the process's allocated address space. [EIO] An I/O error occurred while reading from or writing to the file system. SEE ALSO
chmod(1), open(2), chown(2), stat(2). NOTES
The sticky bit was historically used to lock important executables into memory. 4th Berkeley Distribution May 13, 1986 CHMOD(2)
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CHMOD(2) System Calls Manual CHMOD(2) NAME
chmod - change mode of file SYNOPSIS
chmod(path, mode) char *path; int mode; fchmod(fd, mode) int fd, mode; DESCRIPTION
The file whose name is given by path or referenced by the descriptor fd has its mode changed to mode. Modes are constructed by or'ing together some combination of the following, defined in <sys/inode.h>: ISUID 04000 set user ID on execution ISGID 02000 set group ID on execution ISVTX 01000 `sticky bit' (see below) IREAD 00400 read by owner IWRITE 00200 write by owner IEXEC 00100 execute (search on directory) by owner 00070 read, write, execute (search) by group 00007 read, write, execute (search) by others If an executable file is set up for sharing (this is the default) then mode 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 ISVTX (the `sticky bit') is set on a directory, an unprivileged user may not delete or rename files of other users in that direc- tory. For more details of the properties of the sticky bit, see sticky(8). Only the owner of a file (or the super-user) may change the mode. Writing or changing the owner of a file turns off the set-user-id and set-group-id bits unless the user is the super-user. This makes the system somewhat more secure by protecting set-user-id (set-group-id) files from remaining set-user-id (set-group-id) if they are modified, at the expense of a degree of compatibility. RETURN VALUE
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: [ENOTDIR] A component of the path prefix is not a directory. [EINVAL] The pathname contains a character with the high-order bit set. [ENAMETOOLONG] A component of a pathname exceeded 255 characters, or an entire path name exceeded 1023 characters. [ENOENT] The named file does not exist. [EACCES] Search permission is denied for a component of the path prefix. [ELOOP] Too many symbolic links were encountered in translating the pathname. [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. [EFAULT] Path points outside the process's allocated address space. [EIO] An I/O error occurred while reading from or writing to the file system. Fchmod will fail if: [EBADF] The descriptor is not valid. [EINVAL] Fd refers to a socket, not to a file. [EROFS] The file resides on a read-only file system. [EIO] An I/O error occurred while reading from or writing to the file system. SEE ALSO
chmod(1), open(2), chown(2), stat(2), sticky(8) 4th Berkeley Distribution May 13, 1986 CHMOD(2)