Manual Pages for UNIX Darwin command on man chmod

CHMOD(1) BSD General Commands Manual CHMOD(1)

NAME

cchhmmoodd - change file modes or Access Control Lists

SYNOPSIS

cchhmmoodd [-ffvv] [-RR [-HH | -LL | -PP]] mode file ...

cchhmmoodd [-ffvv] [-RR [-HH | -LL | -PP]] [-a | +a | =a] ACE file ...

cchhmmoodd [-ffvv] [-RR [-HH | -LL | -PP]] [-EE] file ...

cchhmmoodd [-ffvv] [-RR [-HH | -LL | -PP]] [-CC] file ...

cchhmmoodd [-ffvv] [-RR [-HH | -LL | -PP]] [-NN] file ...

DESCRIPTION

The cchhmmoodd utility modifies the file mode bits of the listed files as specified by the mode operand. It may also be used to modify the Access Control Lists (ACLs) associated with the listed files. The generic options are as follows:

-HH If the -RR option is specified, symbolic links on the command line

are followed. (Symbolic links encountered in the tree traversal are not followed by default.)

-LL If the -RR option is specified, all symbolic links are followed.

-PP If the -RR option is specified, no symbolic links are followed.

This is the default.

-RR Change the modes of the file hierarchies rooted in the files

instead of just the files themselves.

-ff Do not display a diagnostic message if cchhmmoodd could not modify the

mode for file.

-vv Cause cchhmmoodd to be verbose, showing filenames as the mode is modi-

fied. If the -vv flag is specified more than once, the old and

new modes of the file will also be printed, in both octal and symbolic notation.

The -HH, -LL and -PP options are ignored unless the -RR option is specified.

In addition, these options override each other and the command's actions are determined by the last one specified.

Only the owner of a file or the super-user is permitted to change the

mode of a file. DIAGNOSTICS The cchhmmoodd utility exits 0 on success, and >0 if an error occurs. MMOODDEESS Modes may be absolute or symbolic. An absolute mode is an octal number constructed from the sum of one or more of the following values:

4000 (the set-user-ID-on-execution bit) Executable files with

this bit set will run with effective uid set to the uid of

the file owner. Directories with the set-user-id bit set

will force all files and sub-directories created in them to

be owned by the directory owner and not by the uid of the creating process, if the underlying file system supports

this feature: see chmod(2) and the suiddir option to

mount(8).

2000 (the set-group-ID-on-execution bit) Executable files with

this bit set will run with effective gid set to the gid of the file owner.

1000 (the sticky bit) See chmod(2) and sticky(8).

0400 Allow read by owner. 0200 Allow write by owner. 0100 For files, allow execution by owner. For directories, allow the owner to search in the directory. 0040 Allow read by group members. 0020 Allow write by group members.

0010 For files, allow execution by group members. For directo-

ries, allow group members to search in the directory. 0004 Allow read by others. 0002 Allow write by others. 0001 For files, allow execution by others. For directories allow others to search in the directory. For example, the absolute mode that permits read, write and execute by the owner, read and execute by group members, read and execute by others,

and no set-uid or set-gid behaviour is 755 (400+200+100+040+010+004+001).

The symbolic mode is described by the following grammar: mode ::= clause [, clause ...] clause ::= [who ...] [action ...] action action ::= op [perm ...] who ::= a | u | g | o

op ::= + | - | =

perm ::= r | s | t | w | x | X | u | g | o The who symbols ``u'', ``g'', and ``o'' specify the user, group, and other parts of the mode bits, respectively. The who symbol ``a'' is equivalent to ``ugo''. The perm symbols represent the portions of the mode bits as follows: r The read bits.

s The set-user-ID-on-execution and set-group-ID-on-execution

bits. t The sticky bit. w The write bits. x The execute/search bits. X The execute/search bits if the file is a directory or any

of the execute/search bits are set in the original (unmodi-

fied) mode. Operations with the perm symbol ``X'' are only meaningful in conjunction with the op symbol ``+'', and are ignored in all other cases. u The user permission bits in the original mode of the file. g The group permission bits in the original mode of the file. o The other permission bits in the original mode of the file. The op symbols represent the operation performed, as follows: + If no value is supplied for perm, the ``+'' operation has no

effect. If no value is supplied for who, each permission bit spec-

ified in perm, for which the corresponding bit in the file mode

creation mask is clear, is set. Otherwise, the mode bits repre-

sented by the specified who and perm values are set.

- If no value is supplied for perm, the ``-'' operation has no

effect. If no value is supplied for who, each permission bit spec-

ified in perm, for which the corresponding bit in the file mode

creation mask is clear, is cleared. Otherwise, the mode bits rep-

resented by the specified who and perm values are cleared. = The mode bits specified by the who value are cleared, or, if no who value is specified, the owner, group and other mode bits are cleared. Then, if no value is supplied for who, each permission bit specified in perm, for which the corresponding bit in the file

mode creation mask is clear, is set. Otherwise, the mode bits rep-

resented by the specified who and perm values are set. Each clause specifies one or more operations to be performed on the mode

bits, and each operation is applied to the mode bits in the order speci-

fied. Operations upon the other permissions only (specified by the symbol ``o'' by itself), in combination with the perm symbols ``s'' or ``t'', are ignored. EEXXAAMMPPLLEESS OOFF VVAALLIIDD MMOODDEESS 644 make a file readable by anyone and writable by the owner only.

go-w deny write permission to group and others.

=rw,+X set the read and write permissions to the usual defaults, but retain any execute permissions that are currently set. +X make a directory or file searchable/executable by everyone if it is already searchable/executable by anyone. 755 u=rwx,go=rx

u=rwx,go=u-w make a file readable/executable by everyone and writable by

the owner only. go= clear all mode bits for group and others.

g=u-w set the group bits equal to the user bits, but clear the

group write bit. AACCLL MMAANNIIPPUULLAATTIIOONN OOPPTTIIOONNSS ACLs are manipulated using extensions to the symbolic mode grammar. Each file has one ACL, containing an ordered list of entries. Each entry refers to a user or group, and grants or denies a set of permissions. The following permissions are applicable to all filesystem objects: delete Delete the item. Deletion may be granted by either this permission on an object or the deletechild right on the containing directory. readattr Read an objects basic attributes. This is implicitly granted if the object can be looked up and not explicitly denied. writeattr Write an object's basic attributes. readextattr Read extended attributes. writeextattr Write extended attributes. readsecurity Read an object's extended security information (ACL). writesecurity Write an object's security information (ownership, mode, ACL). chown Change an object's ownership. The following permissions are applicable to directories: list List entries. search Look up files by name. addfile Add a file. addsubdirectory Add a subdirectory. deletechild Delete a contained object. See the file delete permission above.

The following permissions are applicable to non-directory filesystem

objects: read Open for reading. write Open for writing. append Open for writing, but in a fashion that only allows writes into areas of the file not previously written. execute Execute the file as a script or program. ACL inheritance is controlled with the following permissions words, which may only be applied to directories: fileinherit Inherit to files. directoryinherit Inherit to directories. limitinherit

This flag is only relevant to entries inherited by subdi-

rectories; it causes the directoryinherit flag to be cleared in the entry that is inherited, preventing further nested subdirectories from also inheriting the entry. onlyinherit The entry is inherited by created items but not considered when processing the ACL. The ACL manipulation options are as follows: ++aa The +a mode parses a new ACL entry from the next argument on the commandline and inserts it into the canonical location in the ACL. If the supplied entry refers to an identity already listed, the two entries are combined. EExxaammpplleess

# ls -le

-rw-r-r-+ 1 juser wheel 0 Apr 28 14:06 file1

# chmod +a "admin allow write" file1

# ls -le

-rw-r-r-+ 1 juser wheel 0 Apr 28 14:06 file1

owner: juser 1: admin allow write

# chmod +a "guest deny read" file1

# ls -le

-rw-r-r-+ 1 juser wheel 0 Apr 28 14:06 file1

owner: juser 1: guest deny read 2: admin allow write

# chmod +a "admin allow delete" file1

# ls -le

-rw-r-r-+ 1 juser wheel 0 Apr 28 14:06 file1

owner: juser 1: guest deny read 2: admin allow write,delete The +a mode strives to maintain correct canonical form for the ACL. local deny local allow inherited deny inherited allow

By default, chmod adds entries to the top of the local deny and

local allow lists. Inherited entries are added by using the +ai mode. EExxaammpplleess

# ls -le

-rw-r-r-+ 1 juser wheel 0 Apr 28 14:06 file1

owner: juser 1: guest deny read 2: admin allow write,delete 3: juser inherited deny delete 4: admin inherited allow delete 5: backup inherited deny read

6: admin inherited allow write-security

# chmod +ai "others allow write" file1

# ls -le

-rw-r-r-+ 1 juser wheel 0 Apr 28 14:06 file1

owner: juser 1: guest deny read 2: admin allow write,delete 3: juser inherited deny delete 4: others inherited allow read 5: admin inherited allow delete 6: backup inherited deny read

7: admin inherited allow write-security

++aa## When a specific ordering is required, the exact location at which

an entry will be inserted is specified with the +a# mode.

EExxaammpplleess

# ls -le

-rw-r-r-+ 1 juser wheel 0 Apr 28 14:06 file1

owner: juser 1: guest deny read 2: admin allow write

# chmod +a# 2 "others deny read" file1

# ls -le

-rw-r-r-+ 1 juser wheel 0 Apr 28 14:06 file1

owner: juser 1: guest deny read 2: others deny read 3: admin allow write

The +ai# mode may be used to insert inherited entries at a spe-

cific location. Note that these modes allow non-canonical ACL

ordering to be constructed.

-aa The -a mode is used to delete ACL entries. All entries exactly

matching the supplied entry will be deleted. If the entry lists a subset of rights granted by an entry, only the rights listed are

removed. Entries may also be deleted by index using the -a# mode.

EExxaammpplleess

# ls -le

-rw-r-r-+ 1 juser wheel 0 Apr 28 14:06 file1

owner: juser 1: guest deny read 2: admin allow write,delete

# chmod -a# 1 file1

# ls -le

-rw-r-r-+ 1 juser wheel 0 Apr 28 14:06 file1

owner: juser 1: admin allow write,delete

# chmod -a "admin allow write" file1

# ls -le

-rw-r-r-+ 1 juser wheel 0 Apr 28 14:06 file1

owner: juser 1: admin allow delete

Inheritance is not considered when processing the -a mode; rights

and entries will be removed regardless of their inherited state.

==aa## Individual entries are rewritten using the =a# mode.

EExxaammpplleess

# ls -le

-rw-r-r-+ 1 juser wheel 0 Apr 28 14:06 file1

owner: juser 1: admin allow delete

# chmod =a# 1 "admin allow write,chown"

# ls -le

-rw-r-r-+ 1 juser wheel 0 Apr 28 14:06 file1

owner: juser 1: admin allow write,chown This mode may not be used to add new entries.

-EE Reads the ACL information from stdin, as a sequential list of

ACEs, separated by newlines. If the information parses cor-

rectly, the existing information is replaced.

-CC Returns false if any of the named files have ACLs in non-canoni-

cal order.

-ii Removes the 'inherited' bit from all entries in the named file(s)

ACLs.

-II Removes all inherited entries from the named file(s) ACL(s).

-NN Removes the ACL from the named file(s).

CCOOMMPPAATTIIBBIILLIITTYY

The -vv option is non-standard and its use in scripts is not recommended.

chflags(1), install(1), chmod(2), stat(2), umask(2), fts(3), setmode(3),

symlink(7), chown(8), mount(8), sticky(8) STANDARDS

The cchhmmoodd utility is expected to be IEEE Std 1003.2 (``POSIX.2'') compat-

ible with the exception of the perm symbol ``t'' which is not included in that standard. HISTORY A cchhmmoodd command appeared in Version 1 AT&T UNIX. BSD July 08, 2004 BSD