NAME

chmod — Change files modes

SYNOPSIS

DESCRIPTION

chmod sets the permissions bits given by mode or copying permissions from ref_file on each given file,

mode can be either an octal natural number between 0 and 7777, or a symbolic operation like ‘+r’ or ‘g=o-x’. See the OCTAL MODE and SYMBOLIC OPERATIONS sections for details.

If mode starts with a dash (or is user-provided), it should be broken from options with a preceding double-dash (--) like so:

OPTIONS

-c

Print mode changes

-F ref_file

Copy permission bits from ref_file into each file.

-R

Recurse into directories passed to

-v

Verbose, print both changes and retained modes file

OCTAL MODE

Octal natural number between 0 and 7777, which can be obtained by or'ing the following values:

4000

setuid

2000

setgid

1000

sticky bit

0400

user read

0200

user write

0100

user execute/search

0070

group read, write, execute/search

0007

others read, write, execute/search

SYMBOLIC OPERATIONS

Uses the following grammar:

mode   ::= clause [',' clause]*
clause ::= who* action+
action ::= [op | op perm+ | op permcopy]

who  ::= 'u' | 'g' | 'o' | 'a'
op   ::= '+' | '-' | '='
perm ::= 'r' | 'w' | 'x' | 'X' | 's' | 't'

permcopy ::= 'u' | 'g' | 'o'

Which corresponds to:

mode

List of ‘clause’ to apply, each separated by a comma.

For example ‘g+r,o=g’ sets read permission for group part and copies to other part the resulting permissions of the group part.

clause

Optionally starts with ‘who’ and contains one or more ‘action’.

When ‘who’ isn't given, umask(3) is followed similarly to file creation.

action

Always starts with ‘op’, optionally followed by either one or more ‘perm’, or a single ‘permcopy’

who

user(u), group(g), other(o), all(a)

op

Operation to apply: add(+), del(-), set(=)

When neither ‘perm’ nor ‘permcopy’ were given, set(=) clears all permissions.

perm

which permissions to assign:

r

Read

w

Write

x

Execute/Search

X

Search (directories-only)

s

Setuid when assigned to user, setgid when assigned to group

t

Sticky bit

permcopy

who to copy permissions from: user(u), group(g), other(o)

EXIT STATUS

The chmod utility exits 0 on success, and >0 if an error occurs.

SEE ALSO

stat(1)

STANDARDS

chmod should be compliant with the IEEE Std 1003.1-2024 (“POSIX.1”) specification.

The -c and -v options are present for compatibility with other modern systems such as BusyBox and GNU coreutils. Similarly the -F option was created for compatibility with --reference from GNU, BusyBox and NetBSD while keeping the possibility of using short options.

AUTHORS

Haelwenn (lanodan) Monnier <contact+utils@hacktivis.me>