Linux命令:chmod
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chmod --help
1 Usage: chmod [OPTION]... MODE[,MODE]... FILE... 2 or: chmod [OPTION]... OCTAL-MODE FILE... 3 or: chmod [OPTION]... --reference=RFILE FILE... 4 Change the mode of each FILE to MODE. 5 With --reference, change the mode of each FILE to that of RFILE. 6 7 -c, --changes like verbose but report only when a change is made 8 -f, --silent, --quiet suppress most error messages 9 -v, --verbose output a diagnostic for every file processed 10 --no-preserve-root do not treat '/' specially (the default) 11 --preserve-root fail to operate recursively on '/' 12 --reference=RFILE use RFILE's mode instead of MODE values 13 -R, --recursive change files and directories recursively 14 --help display this help and exit 15 --version output version information and exit 16 17 Each MODE is of the form '[ugoa]*([-+=]([rwxXst]*|[ugo]))+|[-+=][0-7]+'. 18 19 GNU coreutils online help: <http://www.gnu.org/software/coreutils/> 20 For complete documentation, run: info coreutils 'chmod invocation'
man chmod
1 CHMOD(1) User Commands CHMOD(1) 2 3 4 5 NAME 6 chmod - change file mode bits 7 8 SYNOPSIS 9 chmod [OPTION]... MODE[,MODE]... FILE... 10 chmod [OPTION]... OCTAL-MODE FILE... 11 chmod [OPTION]... --reference=RFILE FILE... 12 13 DESCRIPTION 14 This manual page documents the GNU version of chmod. chmod changes the file mode bits of each given file according to mode, which can be either a symbolic representation of 15 changes to make, or an octal number representing the bit pattern for the new mode bits. 16 17 The format of a symbolic mode is [ugoa...][[+-=][perms...]...], where perms is either zero or more letters from the set rwxXst, or a single letter from the set ugo. Multiple 18 symbolic modes can be given, separated by commas. 19 20 A combination of the letters ugoa controls which users' access to the file will be changed: the user who owns it (u), other users in the file's group (g), other users not in 21 the file's group (o), or all users (a). If none of these are given, the effect is as if a were given, but bits that are set in the umask are not affected. 22 23 The operator + causes the selected file mode bits to be added to the existing file mode bits of each file; - causes them to be removed; and = causes them to be added and 24 causes unmentioned bits to be removed except that a directory's unmentioned set user and group ID bits are not affected. 25 26 The letters rwxXst select file mode bits for the affected users: read (r), write (w), execute (or search for directories) (x), execute/search only if the file is a directory 27 or already has execute permission for some user (X), set user or group ID on execution (s), restricted deletion flag or sticky bit (t). Instead of one or more of these let‐ 28 ters, you can specify exactly one of the letters ugo: the permissions granted to the user who owns the file (u), the permissions granted to other users who are members of the 29 file's group (g), and the permissions granted to users that are in neither of the two preceding categories (o). 30 31 A numeric mode is from one to four octal digits (0-7), derived by adding up the bits with values 4, 2, and 1. Omitted digits are assumed to be leading zeros. The first 32 digit selects the set user ID (4) and set group ID (2) and restricted deletion or sticky (1) attributes. The second digit selects permissions for the user who owns the file: 33 read (4), write (2), and execute (1); the third selects permissions for other users in the file's group, with the same values; and the fourth for other users not in the 34 file's group, with the same values. 35 36 chmod never changes the permissions of symbolic links; the chmod system call cannot change their permissions. This is not a problem since the permissions of symbolic links 37 are never used. However, for each symbolic link listed on the command line, chmod changes the permissions of the pointed-to file. In contrast, chmod ignores symbolic links 38 encountered during recursive directory traversals. 39 40 SETUID AND SETGID BITS 41 chmod clears the set-group-ID bit of a regular file if the file's group ID does not match the user's effective group ID or one of the user's supplementary group IDs, unless 42 the user has appropriate privileges. Additional restrictions may cause the set-user-ID and set-group-ID bits of MODE or RFILE to be ignored. This behavior depends on the 43 policy and functionality of the underlying chmod system call. When in doubt, check the underlying system behavior. 44 45 chmod preserves a directory's set-user-ID and set-group-ID bits unless you explicitly specify otherwise. You can set or clear the bits with symbolic modes like u+s and g-s, 46 and you can set (but not clear) the bits with a numeric mode. 47 48 RESTRICTED DELETION FLAG OR STICKY BIT 49 The restricted deletion flag or sticky bit is a single bit, whose interpretation depends on the file type. For directories, it prevents unprivileged users from removing or 50 renaming a file in the directory unless they own the file or the directory; this is called the restricted deletion flag for the directory, and is commonly found on world- 51 writable directories like /tmp. For regular files on some older systems, the bit saves the program's text image on the swap device so it will load more quickly when run; 52 this is called the sticky bit. 53 54 OPTIONS 55 Change the mode of each FILE to MODE. With --reference, change the mode of each FILE to that of RFILE. 56 57 -c, --changes 58 like verbose but report only when a change is made 59 60 -f, --silent, --quiet 61 suppress most error messages 62 63 -v, --verbose 64 output a diagnostic for every file processed 65 66 --no-preserve-root 67 do not treat '/' specially (the default) 68 69 --preserve-root 70 fail to operate recursively on '/' 71 72 --reference=RFILE 73 use RFILE's mode instead of MODE values 74 75 -R, --recursive 76 change files and directories recursively 77 78 --help display this help and exit 79 80 --version 81 output version information and exit 82 83 Each MODE is of the form '[ugoa]*([-+=]([rwxXst]*|[ugo]))+|[-+=][0-7]+'. 84 85 GNU coreutils online help: <http://www.gnu.org/software/coreutils/> Report chmod translation bugs to <http://translationproject.org/team/> 86 87 AUTHOR 88 Written by David MacKenzie and Jim Meyering. 89 90 COPYRIGHT 91 Copyright © 2013 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>. 92 This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. 93 94 SEE ALSO 95 chmod(2) 96 97 The full documentation for chmod is maintained as a Texinfo manual. If the info and chmod programs are properly installed at your site, the command 98 99 info coreutils 'chmod invocation' 100 101 should give you access to the complete manual. 102 103 104 105 GNU coreutils 8.22 October 2018 CHMOD(1)