132 lines
3.2 KiB
Groff
132 lines
3.2 KiB
Groff
.\" Copyright (c) 1980 Regents of the University of California.
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.\" All rights reserved. The Berkeley software License Agreement
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.\" specifies the terms and conditions for redistribution.
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.\"
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.\" @(#)chmod.2 6.5 (Berkeley) 5/13/86
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.\"
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.TH CHMOD 2 "May 13, 1986"
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.UC 4
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.SH NAME
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chmod \- change mode of file
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.SH SYNOPSIS
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.nf
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.ft B
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#include <sys/types.h>
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#include <sys/stat.h>
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int chmod(const char *\fIpath\fP, mode_t \fImode\fP)
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.ig \" You never know
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.PP
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.ft B
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int fchmod(int \fIfd\fP, mode_t \fImode\fP)
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..
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.fi
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.SH DESCRIPTION
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The file whose name
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is given by \fIpath\fP
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.ig
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or referenced by the descriptor
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.I fd
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..
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has its mode changed to
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.IR mode .
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Modes are constructed by
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.IR or 'ing
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together some
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combination of the following, defined in
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.IR <sys/stat.h> :
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.PP
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.RS
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.nf
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.ta \w'S_ISUID\ \ 'u +\w'04000\ \ \ 'u
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S_ISUID 04000 set user ID on execution
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S_ISGID 02000 set group ID on execution
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S_ISVTX 01000 `sticky bit' (see below)
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S_IRWXU 00700 read, write, execute by owner
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S_IRUSR 00400 read by owner
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S_IWUSR 00200 write by owner
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S_IXUSR 00100 execute (search on directory) by owner
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S_IRWXG 00070 read, write, execute by group
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S_IRGRP 00040 read by group
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S_IWGRP 00020 write by group
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S_IXGRP 00010 execute (search on directory) by group
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S_IRWXO 00007 read, write, execute by others
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S_IROTH 00004 read by others
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S_IWOTH 00002 write by others
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S_IXOTH 00001 execute (search on directory) by others
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.fi
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.RE
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.PP
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If mode ISVTX (the `sticky bit') is set on a directory,
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an unprivileged user may not delete or rename
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files of other users in that directory. (Minix-vmd)
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.PP
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Only the owner of a file (or the super-user) may change the mode.
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.PP
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Writing or changing the owner of a file
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turns off the set-user-id and set-group-id bits
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unless the user is the super-user.
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This makes the system somewhat more secure
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by protecting set-user-id (set-group-id) files
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from remaining set-user-id (set-group-id) if they are modified,
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at the expense of a degree of compatibility.
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.SH "RETURN VALUE
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Upon successful completion, a value of 0 is returned.
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Otherwise, a value of \-1 is returned and
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.B errno
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is set to indicate the error.
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.SH "ERRORS
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.B Chmod
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will fail and the file mode will be unchanged if:
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.TP 15
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[ENOTDIR]
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A component of the path prefix is not a directory.
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.TP 15
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[ENAMETOOLONG]
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The path name exceeds PATH_MAX characters.
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.TP 15
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[ENOENT]
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The named file does not exist.
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.TP 15
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[EACCES]
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Search permission is denied for a component of the path prefix.
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.TP 15
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[ELOOP]
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Too many symbolic links were encountered in translating the pathname.
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(Minix-vmd)
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.TP 15
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[EPERM]
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The effective user ID does not match the owner of the file and
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the effective user ID is not the super-user.
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.TP 15
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[EROFS]
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The named file resides on a read-only file system.
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.TP 15
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[EFAULT]
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.I Path
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points outside the process's allocated address space.
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.TP 15
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[EIO]
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An I/O error occurred while reading from or writing to the file system.
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.ig
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.PP
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.I Fchmod
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will fail if:
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.TP 15
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[EBADF]
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The descriptor is not valid.
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.TP 15
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[EROFS]
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The file resides on a read-only file system.
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.TP 15
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[EIO]
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An I/O error occurred while reading from or writing to the file system.
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..
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.SH "SEE ALSO"
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.BR chmod (1),
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.BR open (2),
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.BR chown (2),
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.BR stat (2).
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.SH NOTES
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The sticky bit was historically used to lock important executables into
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memory.
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