Print this page
fchmod is standard
added fchmodat, etc.
*** 1,6 ****
! '\" te
.\" Copyright (c) 2005, Sun Microsystems, Inc. All Rights Reserved.
.\" Copyright 1989 AT&T.
.\" Portions Copyright (c) 2001, the Institute of Electrical and Electronics Engineers, Inc. and The Open Group. All Rights Reserved.
.\" Sun Microsystems, Inc. gratefully acknowledges The Open Group for permission to reproduce portions of its copyrighted documentation. Original documentation from The Open Group can be obtained online at
.\" http://www.opengroup.org/bookstore/.
--- 1,6 ----
! .\" Copyright 2014 Garrett D'Amore <garrett@damore.org>
.\" Copyright (c) 2005, Sun Microsystems, Inc. All Rights Reserved.
.\" Copyright 1989 AT&T.
.\" Portions Copyright (c) 2001, the Institute of Electrical and Electronics Engineers, Inc. and The Open Group. All Rights Reserved.
.\" Sun Microsystems, Inc. gratefully acknowledges The Open Group for permission to reproduce portions of its copyrighted documentation. Original documentation from The Open Group can be obtained online at
.\" http://www.opengroup.org/bookstore/.
*** 7,464 ****
.\" The Institute of Electrical and Electronics Engineers and The Open Group, have given us permission to reprint portions of their documentation. In the following statement, the phrase "this text" refers to portions of the system documentation. Portions of this text are reprinted and reproduced in electronic form in the Sun OS Reference Manual, from IEEE Std 1003.1, 2004 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2004 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between these versions and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html.
.\" This notice shall appear on any product containing this material.
.\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License"). You may not use this file except in compliance with the License.
.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing. See the License for the specific language governing permissions and limitations under the License.
.\" When distributing Covered Code, include this CDDL HEADER in each file and include the License file at usr/src/OPENSOLARIS.LICENSE. If applicable, add the following below this CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your own identifying information: Portions Copyright [yyyy] [name of copyright owner]
! .TH CHMOD 2 "Sep 12, 2005"
! .SH NAME
! chmod, fchmod \- change access permission mode of file
! .SH SYNOPSIS
! .LP
! .nf
! #include <sys/types.h>
! #include <sys/stat.h>
!
! \fBint\fR \fBchmod\fR(\fBconst char *\fR\fIpath\fR, \fBmode_t\fR \fImode\fR);
! .fi
!
! .LP
! .nf
! \fBint\fR \fBfchmod\fR(\fBint\fR \fIfildes\fR, \fBmode_t\fR \fImode\fR);
! .fi
!
! .SH DESCRIPTION
! .sp
! .LP
! The \fBchmod()\fR and \fBfchmod()\fR functions set the access permission
! portion of the mode of the file whose name is given by \fIpath\fR or referenced
! by the open file descriptor \fIfildes\fR to the bit pattern contained in
! \fImode\fR. Access permission bits are interpreted as follows:
! .sp
!
! .sp
! .TS
! l l l
! l l l .
! \fBS_ISUID\fR 04000 Set user ID on execution.
! \fBS_ISGID\fR 020#0 T{
! Set group ID on execution if # is \fB7\fR, \fB5\fR, \fB3\fR, or \fB1\fR. Enable mandatory file/record locking if # is \fB6\fR, \fB4\fR, \fB2\fR, or \fB0\fR.
! T}
! \fBS_ISVTX\fR 01000 Sticky bit.
! \fBS_IRWXU\fR 00700 Read, write, execute by owner.
! \fBS_IRUSR\fR 00400 Read by owner.
! \fBS_IWUSR\fR 00200 Write by owner.
! \fBS_IXUSR\fR 00100 T{
! Execute (search if a directory) by owner.
! T}
! \fBS_IRWXG\fR 00070 Read, write, execute by group.
! \fBS_IRGRP\fR 00040 Read by group.
! \fBS_IWGRP\fR 00020 Write by group.
! \fBS_IXGRP\fR 00010 Execute by group.
! \fBS_IRWXO\fR 00007 Read, write, execute (search) by others.
! \fBS_IROTH\fR 00004 Read by others.
! \fBS_IWOTH\fR 00002 Write by others.
! \fBS_IXOTH\fR 00001 Execute by others.
! .TE
!
! .sp
! .LP
Modes are constructed by the bitwise OR operation of the access permission
bits.
! .sp
! .LP
The effective user ID of the process must match the owner of the file or the
process must have the appropriate privilege to change the mode of a file.
! .sp
! .LP
If the process is not a privileged process and the file is not a directory,
mode bit 01000 (save text image on execution) is cleared.
! .sp
! .LP
If neither the process is privileged nor the file's group is a member of the
process's supplementary group list, and the effective group ID of the process
does not match the group ID of the file, mode bit 02000 (set group ID on
execution) is cleared.
! .sp
! .LP
! If a directory is writable and has \fBS_ISVTX\fR (the sticky bit) set, files
within that directory can be removed or renamed only if one or more of the
! following is true (see \fBunlink\fR(2) and \fBrename\fR(2)):
! .RS +4
! .TP
! .ie t \(bu
! .el o
the user owns the file
! .RE
! .RS +4
! .TP
! .ie t \(bu
! .el o
the user owns the directory
! .RE
! .RS +4
! .TP
! .ie t \(bu
! .el o
the file is writable by the user
! .RE
! .RS +4
! .TP
! .ie t \(bu
! .el o
the user is a privileged user
! .RE
! .sp
! .LP
! If a regular file is not executable and has \fBS_ISVTX\fR set, the file is
assumed to be a swap file. In this case, the system's page cache will not be
! used to hold the file's data. If the \fBS_ISVTX\fR bit is set on any other
! file, the results are unspecified.
! .sp
! .LP
If a directory has the set group ID bit set, a given file created within that
directory will have the same group ID as the directory. Otherwise, the newly
created file's group ID will be set to the effective group ID of the creating
process.
! .sp
! .LP
If the mode bit 02000 (set group ID on execution) is set and the mode bit 00010
(execute or search by group) is not set, mandatory file/record locking will
! exist on a regular file, possibly affecting future calls to \fBopen\fR(2),
! \fBcreat\fR(2), \fBread\fR(2), and \fBwrite\fR(2) on this file.
! .sp
! .LP
! If \fIfildes\fR references a shared memory object, \fBfchmod()\fR need only
! affect the \fBS_IRUSR\fR, \fBS_IRGRP\fR, \fBS_IROTH\fR, \fBS_IWUSR\fR,
! \fBS_IWGRP\fR, \fBS_IWOTH\fR, \fBS_IXUSR\fR, \fBS_IXGRP\fR, and \fBS_IXOTH\fR
file permission bits.
! .sp
! .LP
! If \fIfildes\fR refers to a socket, \fBfchmod()\fR does not fail but no action
! is taken.
! .sp
! .LP
! If \fIfildes\fR refers to a stream that is attached to an object in the file
! system name space with \fBfattach\fR(3C), the \fBfchmod()\fR call performs no
! action and returns successfully.
! .sp
! .LP
! Upon successful completion, \fBchmod()\fR and \fBfchmod()\fR mark for update
! the \fBst_ctime\fR field of the file.
! .SH RETURN VALUES
! .sp
! .LP
! Upon successful completion, \fB0\fR is returned. Otherwise, \fB\(mi1\fR is
! returned, the file mode is unchanged, and \fBerrno\fR is set to indicate the
! error.
! .SH ERRORS
! .sp
! .LP
! The \fBchmod()\fR and \fBfchmod()\fR functions will fail if:
! .sp
! .ne 2
! .na
! \fB\fBEIO\fR\fR
! .ad
! .RS 9n
! An I/O error occurred while reading from or writing to the file system.
! .RE
!
! .sp
! .ne 2
! .na
! \fB\fBEPERM\fR\fR
! .ad
! .RS 9n
! The effective user ID does not match the owner of the file and the process does
! not have appropriate privilege.
! .sp
! The {\fBPRIV_FILE_OWNER\fR} privilege overrides constraints on ownership when
! changing permissions on a file.
! .sp
! The {\fBPRIV_FILE_SETID\fR} privilege overrides constraints on ownership when
! adding the setuid or setgid bits to an executable file or a directory. When
! adding the setuid bit to a root owned executable, additional restrictions
! apply. See \fBprivileges\fR(5).
! .RE
!
! .sp
! .LP
! The \fBchmod()\fR function will fail if:
! .sp
! .ne 2
! .na
! \fB\fBEACCES\fR\fR
! .ad
! .RS 16n
! Search permission is denied on a component of the path prefix of \fIpath\fR.
! The privilege {\fBFILE_DAC_SEARCH\fR} overrides file permissions restrictions
! in that case.
! .RE
!
! .sp
! .ne 2
! .na
! \fB\fBEFAULT\fR\fR
! .ad
! .RS 16n
! The \fIpath\fR argument points to an illegal address.
! .RE
!
! .sp
! .ne 2
! .na
! \fB\fBELOOP\fR\fR
! .ad
! .RS 16n
! A loop exists in symbolic links encountered during the resolution of the
! \fIpath\fR argument.
! .RE
!
! .sp
! .ne 2
! .na
! \fB\fBENAMETOOLONG\fR\fR
! .ad
! .RS 16n
! The length of the \fIpath\fR argument exceeds \fBPATH_MAX\fR, or the length of
! a \fIpath\fR component exceeds \fBNAME_MAX\fR while \fB_POSIX_NO_TRUNC\fR is in
! effect.
! .RE
!
! .sp
! .ne 2
! .na
! \fB\fBENOENT\fR\fR
! .ad
! .RS 16n
! Either a component of the path prefix or the file referred to by \fIpath\fR
! does not exist or is a null pathname.
! .RE
!
! .sp
! .ne 2
! .na
! \fB\fBENOLINK\fR\fR
! .ad
! .RS 16n
! The \fIfildes\fR argument points to a remote machine and the link to that
! machine is no longer active.
! .RE
!
! .sp
! .ne 2
! .na
! \fB\fBENOTDIR\fR\fR
! .ad
! .RS 16n
! A component of the prefix of \fIpath\fR is not a directory.
! .RE
!
! .sp
! .ne 2
! .na
! \fB\fBEROFS\fR\fR
! .ad
! .RS 16n
! The file referred to by \fIpath\fR resides on a read-only file system.
! .RE
!
! .sp
! .LP
! The \fBfchmod()\fR function will fail if:
! .sp
! .ne 2
! .na
! \fB\fBEBADF\fR\fR
! .ad
! .RS 11n
! The \fIfildes\fR argument is not an open file descriptor
! .RE
!
! .sp
! .ne 2
! .na
! \fB\fBENOLINK\fR\fR
! .ad
! .RS 11n
! The \fIpath\fR argument points to a remote machine and the link to that machine
! is no longer active.
! .RE
!
! .sp
! .ne 2
! .na
! \fB\fBEROFS\fR\fR
! .ad
! .RS 11n
! The file referred to by \fIfildes\fR resides on a read-only file system.
! .RE
!
! .sp
! .LP
! The \fBchmod()\fR and \fBfchmod()\fR functions may fail if:
! .sp
! .ne 2
! .na
! \fB\fBEINTR\fR\fR
! .ad
! .RS 10n
! A signal was caught during execution of the function.
! .RE
!
! .sp
! .ne 2
! .na
! \fB\fBEINVAL\fR\fR
! .ad
! .RS 10n
! The value of the \fImode\fR argument is invalid.
! .RE
!
! .sp
! .LP
! The \fBchmod()\fR function may fail if:
! .sp
! .ne 2
! .na
! \fB\fBELOOP\fR\fR
! .ad
! .RS 16n
! More than {\fBSYMLOOP_MAX\fR} symbolic links were encountered during the
! resolution of the \fIpath\fR argument.
! .RE
!
! .sp
! .ne 2
! .na
! \fB\fBENAMETOOLONG\fR\fR
! .ad
! .RS 16n
! As a result of encountering a symbolic link in resolution of the\fIpath\fR
! argument, the length of the substituted pathname strings exceeds
! {\fBPATH_MAX\fR}.
! .RE
!
! .sp
! .LP
! The \fBfchmod()\fR function may fail if:
! .sp
! .ne 2
! .na
! \fB\fBEINVAL\fR\fR
! .ad
! .RS 10n
! The \fIfildes\fR argument refers to a pipe and the system disallows execution
! of this function on a pipe.
! .RE
!
! .SH EXAMPLES
! .LP
! \fBExample 1 \fRSet Read Permissions for User, Group, and Others
! .sp
! .LP
The following example sets read permissions for the owner, group, and others.
!
! .sp
! .in +2
! .nf
#include <sys/stat.h>
const char *path;
\&...
chmod(path, S_IRUSR|S_IRGRP|S_IROTH);
! .fi
! .in -2
!
! .LP
! \fBExample 2 \fRSet Read, Write, and Execute Permissions for the Owner Only
! .sp
! .LP
The following example sets read, write, and execute permissions for the owner,
and no permissions for group and others.
!
! .sp
! .in +2
! .nf
#include <sys/stat.h>
const char *path;
\&...
chmod(path, S_IRWXU);
! .fi
! .in -2
!
! .LP
! \fBExample 3 \fRSet Different Permissions for Owner, Group, and Other
! .sp
! .LP
The following example sets owner permissions for CHANGEFILE to read, write, and
execute, group permissions to read and execute, and other permissions to read.
!
! .sp
! .in +2
! .nf
#include <sys/stat.h>
#define CHANGEFILE "/etc/myfile"
\&...
chmod(CHANGEFILE, S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH);
! .fi
! .in -2
!
! .LP
! \fBExample 4 \fRSet and Checking File Permissions
! .sp
! .LP
The following example sets the file permission bits for a file named
! \fB/home/cnd/mod1\fR, then calls the \fBstat\fR(2) function to verify the
! permissions.
!
! .sp
! .in +2
! .nf
#include <sys/types.h>
#include <sys/stat.h>
int status;
struct stat buffer
\&...
chmod("home/cnd/mod1", S_IRWXU|S_IRWXG|S_IROTH|S_IWOTH);
status = stat("home/cnd/mod1", &buffer;);
! .fi
! .in -2
!
! .SH USAGE
! .sp
! .LP
! If \fBchmod()\fR or \fBfchmod()\fR is used to change the file group owner
permissions on a file with non-trivial ACL entries, only the ACL mask is set to
the new permissions and the group owner permission bits in the file's mode
! field (defined in \fBmknod\fR(2)) are unchanged. A non-trivial ACL entry is
one whose meaning cannot be represented in the file's mode field alone. The new
ACL mask permissions might change the effective permissions for additional
users and groups that have ACL entries on the file.
! .SH ATTRIBUTES
! .sp
! .LP
! See \fBattributes\fR(5) for descriptions of the following attributes:
! .sp
!
! .sp
! .TS
! box;
! c | c
! l | l .
! ATTRIBUTE TYPE ATTRIBUTE VALUE
! _
! Interface Stability Standard
! _
! MT-Level Async-Signal-Safe
! .TE
!
! .SH SEE ALSO
! .sp
! .LP
! \fBchmod\fR(1), \fBchown\fR(2), \fBcreat\fR(2), \fBfcntl\fR(2), \fBmknod\fR(2),
! \fBopen\fR(2), \fBread\fR(2), \fBrename\fR(2), \fBstat\fR(2), \fBwrite\fR(2),
! \fBfattach\fR(3C), \fBmkfifo\fR(3C), \fBstat.h\fR(3HEAD), \fBattributes\fR(5),
! \fBprivileges\fR(5), \fBstandards\fR(5)
! .sp
! .LP
! \fIProgramming Interfaces Guide\fR
--- 7,525 ----
.\" The Institute of Electrical and Electronics Engineers and The Open Group, have given us permission to reprint portions of their documentation. In the following statement, the phrase "this text" refers to portions of the system documentation. Portions of this text are reprinted and reproduced in electronic form in the Sun OS Reference Manual, from IEEE Std 1003.1, 2004 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2004 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between these versions and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html.
.\" This notice shall appear on any product containing this material.
.\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License"). You may not use this file except in compliance with the License.
.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing. See the License for the specific language governing permissions and limitations under the License.
.\" When distributing Covered Code, include this CDDL HEADER in each file and include the License file at usr/src/OPENSOLARIS.LICENSE. If applicable, add the following below this CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your own identifying information: Portions Copyright [yyyy] [name of copyright owner]
! .Dd "Sep 12, 2005"
! .Dt CHMOD 2
! .Os
! .
! .Sh NAME
! .
! .Nm chmod ,
! .Nm fchmod ,
! .Nm fchmodat
! .Nd change access permission mode of file
! .Sh SYNOPSIS
! .In sys/stat.h
! .
! .Ft int
! .Fo chmod
! .Fa "const char *path"
! .Fa "mode_t mode"
! .Fc
! .
! .Ft int
! .Fo fchmod
! .Fa "int fildes"
! .Fa "mode_t mode"
! .Fc
! .Ft int
! .Fo fchmodat
! .Fa "int dirfd"
! .Fa "const char *path"
! .Fa "mode_t mode"
! .Fa "int flag"
! .Fc
! .
! .Sh DESCRIPTION
! .
! The
! .Fn chmod ,
! .Fn fchmod ,
! and
! .Fn fchmodat
! functions set the access permission
! portion of the mode of the file whose name is given by
! .Fa path
! or referenced by the open file descriptor
! .Fa fildes
! to the bit pattern contained in
! .Fa mode .
! .Lp
! Access permission bits are interpreted as follows:
! .Bl -column -offset indent "S_IXOTH" "XXXXX" infinity
! .It Dv S_ISUID Ta 04000 Ta Set user ID on execution.
! .It Dv S_ISGID Ta 020#0 Ta Set group ID on execution if # is
! 7, 5, 3, or 1. Enable mandatory file/record locking if # is
! 6, 4, 2, or 0.
! .It Dv S_ISVTX Ta 01000 Ta Sticky bit.
! .It Dv S_IRWXU Ta 00700 Ta Read, write, execute by owner.
! .It Dv S_IRUSR Ta 00400 Ta Read by owner.
! .It Dv S_IWUSR Ta 00200 Ta Write by owner.
! .It Dv S_IXUSR Ta 00100 Ta Execute (search if a directory) by owner.
! .It Dv S_IRWXG Ta 00070 Ta Read, write, execute by group.
! .It Dv S_IRGRP Ta 00040 Ta Read by group.
! .It Dv S_IWGRP Ta 00020 Ta Write by group.
! .It Dv S_IXGRP Ta 00010 Ta Execute by group.
! .It Dv S_IRWXO Ta 00007 Ta Read, write, execute (search) by others.
! .It Dv S_IROTH Ta 00004 Ta Read by others.
! .It Dv S_IWOTH Ta 00002 Ta Write by others.
! .It Dv S_IXOTH Ta 00001 Ta Execute by others.
! .El
! .Lp
Modes are constructed by the bitwise OR operation of the access permission
bits.
! .Lp
The effective user ID of the process must match the owner of the file or the
process must have the appropriate privilege to change the mode of a file.
! .Lp
If the process is not a privileged process and the file is not a directory,
mode bit 01000 (save text image on execution) is cleared.
! .Lp
If neither the process is privileged nor the file's group is a member of the
process's supplementary group list, and the effective group ID of the process
does not match the group ID of the file, mode bit 02000 (set group ID on
execution) is cleared.
! .Lp
! If a directory is writable and has
! .Dv S_ISVTX
! (the sticky bit) set, files
within that directory can be removed or renamed only if one or more of the
! following is true (see
! .Xr unlink 2
! and
! .Xr rename 2 :
! .Bl -bullet -offset indent
! .It
the user owns the file
! .It
the user owns the directory
! .It
the file is writable by the user
! .It
the user is a privileged user
! .El
! .Lp
! If a regular file is not executable and has
! .Dv S_ISVTX
! set, the file is
assumed to be a swap file. In this case, the system's page cache will not be
! used to hold the file's data. If the
! .Dv S_ISVTX
! bit is set on any other file, the results are unspecified.
! .Lp
If a directory has the set group ID bit set, a given file created within that
directory will have the same group ID as the directory. Otherwise, the newly
created file's group ID will be set to the effective group ID of the creating
process.
! .Lp
If the mode bit 02000 (set group ID on execution) is set and the mode bit 00010
(execute or search by group) is not set, mandatory file/record locking will
! exist on a regular file, possibly affecting future calls to
! .Xr open 2 ,
! .Xr create 2 ,
! .Xr read 2 ,
! and
! .Xr write 2
! on this file.
! .Lp
! If
! .Fa fildes
! references a shared memory object,
! .Fn fchmod
! need only
! affect the
! .Dv S_IRUSR , S_IRGRP , S_IROTH , S_IWUSR, S_IWGRP , S_IWOTH , S_IXUSR ,
! .Dv S_IXGRP ,
! and
! .Dv S_IXOTH
file permission bits.
! .Lp
! If
! .Fa fildes
! refers to a socket, or to a stream that is attached to an object in
! the filesystem name space with
! .Xr fattach 3C ,
! .Fn fchmod
! takes no action and returns successfully.
! .Lp
! Upon successful completion,
! .Fn chmod
! .Fn fchmod
! and
! .Fn fchmodat
! mark for update the
! .Vt st_ctime
! field of the file.
! .Lp
! The
! .Fn fchmodat
! function operates like
! .Fn chmod
! except that if
! .Fa path
! is relative, then the file to be changed is determined relative to
! the open directory presented by
! .Fa dirfd ,
! instead of the current working directory. The special value
! .Dv AT_FDCWD can be supplied for
! .Fa dirfd
! to indicate the current working directory.
! .Lp
! If
! .Fa dirfd
! was opened without
! .Dv O_SEARCH ,
! the
! .Fn fchmodat
! function checks whether directory searches are permitted using the current
! permissions of the underlying directory.
! .Lp
! The
! .Fa flag
! argument is bitwise
! .Sy OR
! of the following flags:
! .Bl -tag -width Dv -offset indent
! .It Dv AT_SYMLINK_NOFOLLOW
! If
! .Fa path
! is a symbolic link, then the mode of the link is changed instead of the
! target.
! .El
! .
! .Sh RETURN VALUES
! .
! Upon successful completion, 0 is returned. Otherwise, \(mi1 is
! returned, the file mode is unchanged, and
! .Va errno
! is set to indicate the error.
! .
! .Sh EXAMPLES
! .
! .Ss Example 1 No Set Read Permissions for User, Group, and Others
The following example sets read permissions for the owner, group, and others.
! .Bd -literal -offset indent
#include <sys/stat.h>
const char *path;
\&...
chmod(path, S_IRUSR|S_IRGRP|S_IROTH);
! .Ed
! .
! .Ss Example 2 No Set Read, Write, and Execute Permissions for the Owner Only
The following example sets read, write, and execute permissions for the owner,
and no permissions for group and others.
! .Bd -literal -offset indent
#include <sys/stat.h>
const char *path;
\&...
chmod(path, S_IRWXU);
! .Ed
! .
! .Ss Example 3 No Set Different Permissions for Owner, Group, and Other
The following example sets owner permissions for CHANGEFILE to read, write, and
execute, group permissions to read and execute, and other permissions to read.
! .Bd -literal -offset indent
#include <sys/stat.h>
#define CHANGEFILE "/etc/myfile"
\&...
chmod(CHANGEFILE, S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH);
! .Ed
! .Ss Example 4 No Set and Checking File Permissions
The following example sets the file permission bits for a file named
! .Pa /home/cnd/mod1 ,
! then calls the
! .Xr stat 2
! function to verify the permissions.
! .Bd -literal -offset indent
#include <sys/types.h>
#include <sys/stat.h>
int status;
struct stat buffer
\&...
chmod("home/cnd/mod1", S_IRWXU|S_IRWXG|S_IROTH|S_IWOTH);
status = stat("home/cnd/mod1", &buffer;);
! .Ed
! .
! .Sh ERRORS
! .
! The
! .Fn chmod ,
! .Fn fchmod
! and
! .Fn fchmodat
! functions will fail if:
! .Bl -tag -width Er
! .It Er EIO
! An I/O error occurred while reading from or writing to the file system.
! .It Er EPERM
! The effective user ID does not match the owner of the file and the process does
! not have appropriate privilege.
! .Lp
! The
! .Brq Dv PRIV_FILE_OWNER
! privilege overrides constraints on ownership when
! changing permissions on a file.
! .Lp
! The
! .Brq Dv PRIV_FILE_SETID
! privilege overrides constraints on ownership when
! adding the setuid or setgid bits to an executable file or a directory. When
! adding the setuid bit to a root owned executable, additional restrictions
! apply. See
! .Xr privileges 5 .
! .El
! .Lp
! The
! .Fn chmod
! and
! .Fn fchmodat
! functions will fail if:
! .Bl -tag -width Er
! .
! .It Er EACCES
! Search permission is denied on a component of the path prefix of
! .Fa path .
! The privilege
! .Brq Dv FILE_DAC_SEARCH
! overrides file permissions restrictions in that case.
! .
! .It Er EFAULT
! The
! .Fa path
! argument points to an illegal address.
! .
! .It Er ELOOP
! A loop exists in symbolic links encountered during the resolution of the
! .Fa path
! argument.
! .
! .It Er ENAMETOOLONG
! The length of the
! .Fa path
! argument exceeds
! .Brq Dv PATH_MAX .
! .
! .It Er NOENT
! Either a component of the path prefix or the file referred to by
! .Fa path
! does not exist or is a null pathname.
! .
! .It Er ENOLINK
! The
! .Fa path
! argument points to a remote machine and the link to that
! machine is no longer active.
! .
! .It Er ENOTDIR
! A component of the prefix of
! .Fa path
! is not a directory.
! .
! .It Er EROFS
! The file referred to by
! .Fa path
! resides on a read-only file system.
! .El
! .Lp
! The
! .Fn fchmod
! function will fail if:
! .Bl -tag -width Er
! .
! .It Er EBADF
! The
! .Fa filedes
! argument is not an open file descriptor
! .
! .It Er ENOLINK
! The file referred to by
! .Fa filedes
! argument points to a remote machine and the link to that machine
! is no longer active.
! .
! .It Er EROFS
! The file referred to by
! .Fa fildes
! resides on a read-only file system.
! .El
! .Lp
! The
! .Fn fchmodat
! function will fail if:
! .Bl -tag -width Er
! .
! .It Er EBADF
! The
! .Fa path
! argument does not specify an absolute path, and
! .Fa dirfd
! is neither
! .Dv AT_FDCWD
! nor a file descriptor open for reading or searching.
! .
! .It Er EACCES
! The
! .Fa dirfd
! descriptor was opened without
! .Dv O_SEARCH
! and the underlying directory permissions do not allow directory
! searches.
! .El
! .
! .Lp
! The
! .Fn chmod ,
! .Fn fchmod ,
! and
! .Fn fchmodat
! functions may fail if:
! .Bl -tag -width Er
! .
! .It Er EINTR
! A signal was caught during execution of the function.
! .
! .It Er EINVAL
! The value of the
! .Fa mode
! argument is invalid.
! .El
! .Lp
! The
! .Fn chmod
! and
! .Fn fchmodat
! functions may fail if:
! .Bl -tag -width Er
! .
! .It Er ELOOP
! More than
! .Brq Dv SYMLOOP_MAX
! symbolic links were encountered during the
! resolution of the
! .Fa path
! argument.
! .
! .It Er ENAMETOOLONG
! As a result of encountering a symbolic link in resolution of the
! .Fa path
! argument, the length of the substituted pathname exceed
! .Brq Dv PATH_MAX .
! .El
! .Lp
! The
! .Fn fchmod
! function may fail if:
! .Bl -tag -width Er
! .It EINVAL
! The
! .Fa fildes
! argument refers to a pipe and the system disallows execution
! of this function on a pipe.
! .El
! .
! .Lp
! The
! .Fn fchmodat
! function may fail if:
! .Bl -tag -width Er
! .It Er EINVAL
! The value of
! .Fa flag
! is invalid.
! .It Er ENOTDIR
! The
! .Fa dirfd
! argument is not a file descriptor opened on a directory or
! the special value
! .Dv AT_CWDFD ,
! and
! .Fa path
! is not an absolute directory name.
! .It Er EOPNOTSUPP
! The
! .Fa flag
! argument contains the bit
! .Dv AT_SYMLINK_NOFOLLOW ,
! the
! .Fa path
! is a symbolic link, and the underlying filesystem does not support
! changing the mode of symbolic links.
! .El
! .
! .Sh USAGE
! If
! .Fn chmod ,
! .Fn fchmod ,
! or
! .Fn fchmodat
! are used to change the file group owner
permissions on a file with non-trivial ACL entries, only the ACL mask is set to
the new permissions and the group owner permission bits in the file's mode
! field (defined in
! .Xr mknod 2 )
! are unchanged. A non-trivial ACL entry is
one whose meaning cannot be represented in the file's mode field alone. The new
ACL mask permissions might change the effective permissions for additional
users and groups that have ACL entries on the file.
! .Lp
! The
! .Fn fchmodat
! function is intended to enable changing permissions in directories other than
! the current working directory without race conditions.
! .
! .Sh INTERFACE STABILITY
! .
! .Sy Standard .
! .
! .Sh MT-LEVEL
! .
! .Sy Async-Signal-Safe .
! .
! .Sh SEE ALSO
! .
! .Xr chmod 1 ,
! .Xr chown 2 ,
! .Xr creat 2 ,
! .Xr fcntl 2 ,
! .Xr mknod 2 ,
! .Xr open 2 ,
! .Xr read 2 ,
! .Xr rename 2 ,
! .Xr stat 2 ,
! .Xr write 2 ,
! .Xr fattach 3C ,
! .Xr mkfifo 3C ,
! .Xr stat.h 3HEAD ,
! .Xr privileges 5 ,
! .Xr standards 5
! .Rs
! .%T Programming Interfaces Guide
! .Re
! .
! .Sh STANDARDS
! .
! The
! .Fn chmod
! function was introduced in
! .At
! and is specified in
! .St -p1003.1 .
! The
! .Fn fchmod
! function was introduced in
! .St -xpg4.2 .
! The
! .Fn fchmodat
! function was introduced in
! .St -p1003.1-2008 .