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<!-- TITLE=Linux Complete Command Reference//-->
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<a href="0744-0746.html">Previous</A> | <a href="../ewtoc.html">Table of Contents</A> | <a href="0751-0753.html">Next</A></CENTER></P>
<A NAME="PAGENUM-747"><P>Page 747</P></A>
<!-- CODE SNIP //-->
<PRE>
#include <asm/cachectl.h>
int cacheflush(char *addr,intnbytes,intcache);
</PRE>
<!-- END CODE SNIP //-->
<P><B>
DESCRIPTION
</B></P>
<P>cacheflush flushes contents of indicated cache(s) for user addresses in the range
addr to (addr+nbytes-1). The cache may be one of the following:
</P>
<TABLE>
<TR><TD>
ICACHE
</TD><TD>
Flush the instruction cache.
</TD></TR><TR><TD>
DCACHE
</TD><TD>
Write back to memory and invalidate the affected valid cache lines.
</TD></TR><TR><TD>
BCACHE
</TD><TD>
Same as (ICACHE|DCACHE).
</TD></TR></TABLE>
<P><B>
RETURN VALUE
</B></P>
<P>cacheflush returns 0 on success or -1 on error. If errors are detected,
errno will indicate the error.
</P>
<P><B>
ERRORS
</B></P>
<TABLE>
<TR><TD>
EINVAL
</TD><TD>
The cache parameter is not one of
ICACHE, DCACHE, or BCACHE.
</TD></TR><TR><TD>
EFAULT
</TD><TD>
Some or all of the address range addr to
(addr+nbytes-1) is not accessible.
</TD></TR></TABLE>
<P><B>
BUGS
</B></P>
<P>The current implementation ignores the addr and
nbytes parameters. Therefore, the whole cache is always flushed.
</P>
<P><B>
NOTE
</B></P>
<P>This system call is only available on MIPS-based systems.
</P>
<P><B>
SEE ALSO
</B></P>
<!-- CODE SNIP //-->
<PRE>
cachectl(2)
</PRE>
<!-- END CODE SNIP //-->
<P>
Linux, 27 June 95
</P>
<H3><A NAME="ch02_ 13">
chdir, fchdir
</A></H3>
<P>chdir, fchdir—Changes the working directory
</P>
<P><B>
SYNOPSIS
</B></P>
<!-- CODE SNIP //-->
<PRE>
#include <unistd.h>
int chdir(const char *path);
int fchdir(int fd);
</PRE>
<!-- END CODE SNIP //-->
<P><B>
DESCRIPTION
</B></P>
<P>chdir changes the current directory to that specified in
path.
</P>
<P>fchdir is identical to chdir, only the directory is given as an open file descriptor.
</P>
<P><B>
RETURN VALUE
</B></P>
<P>On success, 0 is returned. On error, _1 is returned, and
errno is set appropriately.
</P>
<P><B>
ERRORS
</B></P>
<P>Depending on the file system, other errors can be returned. The more general errors are listed here:
</P>
<TABLE>
<TR><TD>
EPERM
</TD><TD>
The process does not have execute permission on the directory.
</TD></TR><TR><TD>
EFAULT
</TD><TD>
path points outside your accessible address space.
</TD></TR><TR><TD>
ENAMETOOLONG
</TD><TD>
path is too long.
</TD></TR></TABLE>
<A NAME="PAGENUM-748"><P>Page 748</P></A>
<TABLE>
<TR><TD>
EBADF
</TD><TD>
fd is not a valid file descriptor.
</TD></TR><TR><TD>
ENOENT
</TD><TD>
The file does not exist.
</TD></TR><TR><TD>
ENOMEM
</TD><TD>
Insufficient kernel memory was available.
</TD></TR><TR><TD>
ENOTDIR
</TD><TD>
A component of the path prefix is not a directory.
</TD></TR><TR><TD>
EACCES
</TD><TD>
Search permission is denied on a component of the path prefix.
</TD></TR><TR><TD>
ELOOP
</TD><TD>
path contains a circular reference (that is, via a symbolic link)
</TD></TR></TABLE>
<P><B>
SEE ALSO
</B></P>
<!-- CODE SNIP //-->
<PRE>
getcwd(3), chroot(2)
</PRE>
<!-- END CODE SNIP //-->
<P>Linux 1.2.4, 15 April 1995
</P>
<H3><A NAME="ch02_ 14">
chmod, fchmod
</A></H3>
<P>chmod, fchmod—Changes permissions of a file
</P>
<P><B>
SYNOPSIS
</B></P>
<!-- CODE SNIP //-->
<PRE>
#include <sys/types.h>
#include <sys/stat.h>
int chmod(const char *path,modetmode);
int fchmod(int fildes,modetmode);
</PRE>
<!-- END CODE SNIP //-->
<P><B>
DESCRIPTION
</B></P>
<P>The mode of the file given by path or referenced by
filedes is changed.
</P>
<P>Modes are specified by oring the following:
</P>
<TABLE>
<TR><TD>
S_ISUID
</TD><TD>
04000 Set user ID on execution
</TD></TR><TR><TD>
S_ISGID
</TD><TD>
02000 Set group ID on execution
</TD></TR><TR><TD>
S_ISVTX
</TD><TD>
01000 Sticky bit
</TD></TR><TR><TD>
S_IRUSR (S_IREAD)
</TD><TD>
00400 Read by owner
</TD></TR><TR><TD>
S_IWUSR (S_IWRITE)
</TD><TD>
00200 Write by owner
</TD></TR><TR><TD>
S_IXUSR (S_IEXEC)
</TD><TD>
00100 Execute/search by owner
</TD></TR><TR><TD>
S_IRGRP
</TD><TD>
00040 Read by group
</TD></TR><TR><TD>
S_IWGRP
</TD><TD>
00020 Write by group
</TD></TR><TR><TD>
S_IXGRP
</TD><TD>
00010 Execute/search by group
</TD></TR><TR><TD>
S_IROTH
</TD><TD>
00004 Read by others
</TD></TR><TR><TD>
S_IWOTH
</TD><TD>
00002 Write by others
</TD></TR><TR><TD>
S_IXOTH
</TD><TD>
00001 Execute/search by others
</TD></TR><TR><TD>
</TD><TD>
The effective UID of the process must be 0 or must match the owner of the file.
</TD></TR><TR><TD>
</TD><TD>
The effective UID or GID must be appropriate for setting execution bits.
</TD></TR><TR><TD>
</TD><TD>
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 superuser can set the sticky bit,
which may have a special meaning (that is, for directories, a file can only be deleted by the
owner or the superuser).
</TD></TR></TABLE>
<P><B>
RETURN VALUE
</B></P>
<P>On success, 0 is returned. On error, _1 is returned and
errno is set appropriately.
</P>
<A NAME="PAGENUM-749"><P>Page 749</P></A>
<P><B>
ERRORS
</B></P>
<P>Depending on the file system, other errors can be returned. The more general errors for
chmod are listed here:
</P>
<TABLE>
<TR><TD>
EPERM
</TD><TD>
The effective UID does not match the owner of the file and is not 0.
</TD></TR><TR><TD>
EROFS
</TD><TD>
The named file resides on a read-only file system.
</TD></TR><TR><TD>
EFAULT
</TD><TD>
path points outside your accessible address space.
</TD></TR><TR><TD>
ENAMETOOLONG
</TD><TD>
path is too long.
</TD></TR><TR><TD>
ENOENT
</TD><TD>
The file does not exist.
</TD></TR><TR><TD>
ENOMEM
</TD><TD>
Insufficient kernel memory was available.
</TD></TR><TR><TD>
ENOTDIR
</TD><TD>
A component of the path prefix is not a directory.
</TD></TR><TR><TD>
EACCES
</TD><TD>
Search permission is denied on a component of the path prefix.
</TD></TR><TR><TD>
ELOOP
</TD><TD>
path contains a circular reference (that is, via a symbolic link)
</TD></TR></TABLE>
<P>The general errors for fchmod are listed here:
</P>
<TABLE>
<TR><TD>
EBADF
</TD><TD>
The descriptor is not value.
</TD></TR><TR><TD>
ENOENT
</TD><TD>
See above.
</TD></TR><TR><TD>
EPERM
</TD><TD>
See above.
</TD></TR><TR><TD>
EROFS
</TD><TD>
See above.
</TD></TR></TABLE>
<P><B>
SEE ALSO
</B></P>
<!-- CODE SNIP //-->
<PRE>
open(2), chown(2), stat(2)
</PRE>
<!-- END CODE SNIP //-->
<P>Linux 0.99.11, 21 July 1993
</P>
<H3><A NAME="ch02_ 15">
chown, fchown
</A></H3>
<P>chown, fchown—Changes ownership of a file
</P>
<P><B>
SYNOPSIS
</B></P>
<!-- CODE SNIP //-->
<PRE>
#include <sys/types.h>
#include <unistd.h>
int chown(const char *path, uid t owner, gid_t group);
int fchown(int fd, uid t owner, gid_t group);
</PRE>
<!-- END CODE SNIP //-->
<P><B>
DESCRIPTION
</B></P>
<P>The owner of the file specified by path or by
fd is changed. Only the superuser may change the owner of a file. The owner
of a file may change the group of the file to any group of which that owner is a member. The superuser may change the
group arbitrarily.
</P>
<P>If the owner or group is specified as _1, that ID is not changed.
</P>
<P><B>
RETURN VALUE
</B></P>
<P>On success, 0 is returned. On error, _1 is returned and
errno is set appropriately.
</P>
<P><B>
ERRORS
</B></P>
<P>Depending on the file system, other errors can be returned. The more general errors for
chown are listed here:
</P>
<TABLE>
<TR><TD>
EPERM
</TD><TD>
The effective UID does not match the owner of the file, and is not 0; or the
owner or group were specified incorrectly.
</TD></TR><TR><TD>
EROFS
</TD><TD>
The named file resides on a read-only file system.
</TD></TR><TR><TD>
EFAULT
</TD><TD>
path points outside your accessible address space.
</TD></TR></TABLE>
<A NAME="PAGENUM-750"><P>Page 750</P></A>
<TABLE>
<TR><TD>
ENAMETOOLONG
</TD><TD>
path is too long.
</TD></TR><TR><TD>
ENOENT
</TD><TD>
The file does not exist.
</TD></TR><TR><TD>
ENOMEM
</TD><TD>
Insufficient kernel memory was available.
</TD></TR><TR><TD>
ENOTDIR
</TD><TD>
A component of the path prefix is not a directory.
</TD></TR><TR><TD>
EACCES
</TD><TD>
Search permission is denied on a component of the path prefix.
</TD></TR><TR><TD>
ELOOP
</TD><TD>
path contains a circular reference (that is, via a symbolic link).
</TD></TR></TABLE>
<P>The general errors for fchown are listed here:
</P>
<TABLE>
<TR><TD>
EBADF
</TD><TD>
The descriptor is not value.
</TD></TR><TR><TD>
ENOENT
</TD><TD>
See above.
</TD></TR><TR><TD>
EPERM
</TD><TD>
See above.
</TD></TR><TR><TD>
EROFS
</TD><TD>
See above.
</TD></TR></TABLE>
<P><B>
NOTES
</B></P>
<P>chown does not follow symbolic links. The prototype for
fchown is only available if USE BSD is defined.
</P>
<P><B>
SEE ALSO
</B></P>
<!-- CODE SNIP //-->
<PRE>
chmod(2), flock(2)
</PRE>
<!-- END CODE SNIP //-->
<P>Linux 0.99.11, 21 July 1993
</P>
<H3><A NAME="ch02_ 16">
chroot
</A></H3>
<P>chroot—Changes root directory
</P>
<P><B>
SYNOPSIS
</B></P>
<!-- CODE SNIP //-->
<PRE>
#include <unistd.h>
int chroot(const char *path);
</PRE>
<!-- END CODE SNIP //-->
<P><B>
DESCRIPTION
</B></P>
<P>chroot changes the root directory to that specified in
path. This directory will be used for pathnames beginning with
/. The root directory is inherited by all children of the current process.
</P>
<P>Only the superuser may change the root directory.
</P>
<P>Note that this call does not change the current working directory, so that
. can be outside the tree rooted at /.
</P>
<P><B>
RETURN VALUE
</B></P>
<P>On success, 0 is returned. On error, _1 is returned and
errno is set appropriately.
</P>
<P><B>
ERRORS
</B></P>
<P>Depending on the file system, other errors can be returned. The more general errors are listed here:
</P>
<TABLE>
<TR><TD>
EPERM
</TD><TD>
The effective UID does not match the owner of the file, and is not 0; or the
owner or group were specified incorrectly.
</TD></TR><TR><TD>
EROFS
</TD><TD>
The named file resides on a read-only file system.
</TD></TR><TR><TD>
EFAULT
</TD><TD>
path points outside your accessible address space.
</TD></TR><TR><TD>
ENAMETOOLONG
</TD><TD>
path is too long.
</TD></TR><TR><TD>
ENOENT
</TD><TD>
The file does not exist.
</TD></TR><TR><TD>
ENOMEM
</TD><TD>
Insufficient kernel memory was available.
</TD></TR></TABLE>
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