.\" Hey Emacs! This file is -*- nroff -*- source. .\" .\" Copyright (c) 1992 Drew Eckhardt (drew@cs.colorado.edu), March 28, 1992 .\" .\" Permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" Permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one .\" .\" Since the Linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. The author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. The author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" Formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" .\" Modified by Michael Haardt (u31b3hs@pool.informatik.rwth-aachen.de) .\" Modified Wed Jul 21 20:18:11 1993 by Rik Faith (faith@cs.unc.edu) .\" Modified Sun Jan 12 14:31:17 MET 1997 by Michael Haardt (michael@cantor.informatik.rwth-aachen.de): NFS details .\" .TH CHMOD 2 "January 12, 1997" "" "System calls" .SH NAME chmod, fchmod \- change permissions of a file .SH SYNOPSIS .B #include .br .B #include .sp .BI "int chmod(const char *" path ", mode_t " mode ); .br .BI "int fchmod(int " fildes ", mode_t " mode ); .SH DESCRIPTION The mode of the file given by .I path or referenced by .I filedes is changed. Modes are specified by .IR or'ing the following: .RS .sp .TP 1.0i S_ISUID 04000 set user ID on execution .TP S_ISGID 02000 set group ID on execution .TP S_ISVTX 01000 sticky bit .TP S_IRUSR (S_IREAD) 00400 read by owner .TP S_IWUSR (S_IWRITE) 00200 write by owner .TP S_IXUSR (S_IEXEC) 00100 execute/search by owner .TP S_IRGRP 00040 read by group .TP S_IWGRP 00020 write by group .TP S_IXGRP 00010 execute/search by group .TP S_IROTH 00004 read by others .TP S_IWOTH 00002 write by others .TP S_IXOTH 00001 execute/search by others .sp .RE The effective UID of the process must be zero or must match the owner of the file. The effective UID or GID must be appropriate for setting execution bits. Depending on the file system, set user ID and set group ID execution bits may be turned off if a file is written. On some file systems, only the super-user can set the sticky bit, which may have a special meaning (i.e., for directories, a file can only be deleted by the owner or the super-user). On NFS file systems, restricting the permissions will immediately influence already open files, because the access control is done on the server, but open files are maintained by the client. Widening the permissions may be delayed for other clients if attribute caching is enabled on them. .SH "RETURN VALUE" On success, zero is returned. On error, \-1 is returned, and .I errno is set appropriately. .SH ERRORS Depending on the file system, other errors can be returned. The more general errors for .B chmod are listed below: .TP 0.8i .B EPERM The effective UID does not match the owner of the file, and is not zero. .TP .B EROFS The named file resides on a read-only file system. .TP .B EFAULT .I path points outside your accessible address space. .TP .B ENAMETOOLONG .I path is too long. .TP .B ENOENT The file does not exist. .TP .B ENOMEM Insufficient kernel memory was available. .TP .B ENOTDIR A component of the path prefix is not a directory. .TP .B EACCES Search permission is denied on a component of the path prefix. .TP .B ELOOP .I path contains a circular reference (i.e., via a symbolic link) .PP The general errors for .B fchmod are listed below: .TP 0.8i .B EBADF The descriptor is not valid. .TP .B ENOENT See above. .B EIO A low-level I/O error occurred while modifying the inode. .SH "CONFORMING TO" The .B chmod call conforms to SVr4, SVID, POSIX, X/OPEN, 4.4BSD. SVr4 documents EINTR, ENOLINK and EMULTIHOP returns, but no ENOMEM. POSIX.1 does not document ENOMEM or ELOOP error conditions. .PP The .B fchmod call conforms to 4.4BSD and SVr4. SVr4 documents additional EIO, EINTR, and ENOLINK error conditions. .PP POSIX and X/OPEN do not document the sticky bit. .TP .B EPERM See above. .TP .B EROFS See above. .SH "CONFORMING TO" \fBchmod\fP conforms to POSIX, but \fBS_ISVTX\fP (the sticky bit) does not, neither do the macros \fBS_IREAD\fP, \fBS_IWRITE\fP and \fBS_IEXEC\fP. POSIX specifies that some implementations may ignore \fBS_ISUID\fP and \fBS_ISGID\fP. Further according to POSIX, you should not attempt to set any bits which are not listed above. .SH "SEE ALSO" .BR open "(2), " chown "(2), " stat "(2) "