| 1 | .\" Copyright (c) 1980 Regents of the University of California.
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| 2 | .\" All rights reserved. The Berkeley software License Agreement
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| 3 | .\" specifies the terms and conditions for redistribution.
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| 4 | .\"
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| 5 | .\" @(#)chmod.2 6.5 (Berkeley) 5/13/86
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| 6 | .\"
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| 7 | .TH CHMOD 2 "May 13, 1986"
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| 8 | .UC 4
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| 9 | .SH NAME
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| 10 | chmod \- change mode of file
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| 11 | .SH SYNOPSIS
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| 12 | .nf
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| 13 | .ft B
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| 14 | #include <sys/types.h>
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| 15 | #include <sys/stat.h>
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| 16 |
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| 17 | int chmod(const char *\fIpath\fP, mode_t \fImode\fP)
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| 18 | .ig \" You never know
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| 19 | .PP
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| 20 | .ft B
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| 21 | int fchmod(int \fIfd\fP, mode_t \fImode\fP)
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| 22 | ..
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| 23 | .fi
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| 24 | .SH DESCRIPTION
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| 25 | The file whose name
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| 26 | is given by \fIpath\fP
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| 27 | .ig
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| 28 | or referenced by the descriptor
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| 29 | .I fd
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| 30 | ..
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| 31 | has its mode changed to
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| 32 | .IR mode .
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| 33 | Modes are constructed by
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| 34 | .IR or 'ing
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| 35 | together some
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| 36 | combination of the following, defined in
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| 37 | .IR <sys/stat.h> :
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| 38 | .PP
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| 39 | .RS
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| 40 | .nf
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| 41 | .ta \w'S_ISUID\ \ 'u +\w'04000\ \ \ 'u
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| 42 | S_ISUID 04000 set user ID on execution
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| 43 | S_ISGID 02000 set group ID on execution
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| 44 | S_ISVTX 01000 `sticky bit' (see below)
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| 45 | S_IRWXU 00700 read, write, execute by owner
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| 46 | S_IRUSR 00400 read by owner
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| 47 | S_IWUSR 00200 write by owner
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| 48 | S_IXUSR 00100 execute (search on directory) by owner
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| 49 | S_IRWXG 00070 read, write, execute by group
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| 50 | S_IRGRP 00040 read by group
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| 51 | S_IWGRP 00020 write by group
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| 52 | S_IXGRP 00010 execute (search on directory) by group
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| 53 | S_IRWXO 00007 read, write, execute by others
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| 54 | S_IROTH 00004 read by others
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| 55 | S_IWOTH 00002 write by others
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| 56 | S_IXOTH 00001 execute (search on directory) by others
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| 57 | .fi
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| 58 | .RE
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| 59 | .PP
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| 60 | If mode ISVTX (the `sticky bit') is set on a directory,
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| 61 | an unprivileged user may not delete or rename
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| 62 | files of other users in that directory. (Minix-vmd)
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| 63 | .PP
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| 64 | Only the owner of a file (or the super-user) may change the mode.
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| 65 | .PP
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| 66 | Writing or changing the owner of a file
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| 67 | turns off the set-user-id and set-group-id bits
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| 68 | unless the user is the super-user.
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| 69 | This makes the system somewhat more secure
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| 70 | by protecting set-user-id (set-group-id) files
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| 71 | from remaining set-user-id (set-group-id) if they are modified,
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| 72 | at the expense of a degree of compatibility.
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| 73 | .SH "RETURN VALUE
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| 74 | Upon successful completion, a value of 0 is returned.
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| 75 | Otherwise, a value of \-1 is returned and
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| 76 | .B errno
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| 77 | is set to indicate the error.
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| 78 | .SH "ERRORS
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| 79 | .B Chmod
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| 80 | will fail and the file mode will be unchanged if:
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| 81 | .TP 15
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| 82 | [ENOTDIR]
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| 83 | A component of the path prefix is not a directory.
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| 84 | .TP 15
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| 85 | [ENAMETOOLONG]
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| 86 | The path name exceeds PATH_MAX characters.
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| 87 | .TP 15
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| 88 | [ENOENT]
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| 89 | The named file does not exist.
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| 90 | .TP 15
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| 91 | [EACCES]
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| 92 | Search permission is denied for a component of the path prefix.
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| 93 | .TP 15
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| 94 | [ELOOP]
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| 95 | Too many symbolic links were encountered in translating the pathname.
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| 96 | (Minix-vmd)
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| 97 | .TP 15
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| 98 | [EPERM]
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| 99 | The effective user ID does not match the owner of the file and
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| 100 | the effective user ID is not the super-user.
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| 101 | .TP 15
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| 102 | [EROFS]
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| 103 | The named file resides on a read-only file system.
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| 104 | .TP 15
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| 105 | [EFAULT]
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| 106 | .I Path
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| 107 | points outside the process's allocated address space.
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| 108 | .TP 15
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| 109 | [EIO]
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| 110 | An I/O error occurred while reading from or writing to the file system.
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| 111 | .ig
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| 112 | .PP
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| 113 | .I Fchmod
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| 114 | will fail if:
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| 115 | .TP 15
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| 116 | [EBADF]
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| 117 | The descriptor is not valid.
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| 118 | .TP 15
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| 119 | [EROFS]
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| 120 | The file resides on a read-only file system.
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| 121 | .TP 15
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| 122 | [EIO]
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| 123 | An I/O error occurred while reading from or writing to the file system.
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| 124 | ..
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| 125 | .SH "SEE ALSO"
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| 126 | .BR chmod (1),
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| 127 | .BR open (2),
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| 128 | .BR chown (2),
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| 129 | .BR stat (2).
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| 130 | .SH NOTES
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| 131 | The sticky bit was historically used to lock important executables into
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| 132 | memory.
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