.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "TRUNCATE" 3P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" truncate 
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
.SH NAME
truncate \- truncate a file to a specified length
.SH SYNOPSIS
.LP
\fB#include <unistd.h>
.br
.sp
int truncate(const char *\fP\fIpath\fP\fB, off_t\fP \fIlength\fP\fB);
\fP
\fB
.br
\fP
.SH DESCRIPTION
.LP
The \fItruncate\fP() function shall cause the regular file named by
\fIpath\fP to have a size which shall be equal to
\fIlength\fP bytes.
.LP
If the file previously was larger than \fIlength\fP, the extra data
is discarded. If the file was previously shorter than
\fIlength\fP, its size is increased, and the extended area appears
as if it were zero-filled.
.LP
The application shall ensure that the process has write permission
for the file.
.LP
If the request would cause the file size to exceed the soft file size
limit for the process, the request shall fail and the
implementation shall generate the SIGXFSZ signal for the process.
.LP
This function shall not modify the file offset for any open file descriptions
associated with the file. Upon successful
completion, if the file size is changed, this function shall mark
for update the \fIst_ctime\fP and \fIst_mtime\fP fields of the
file, and the S_ISUID and S_ISGID bits of the file mode may be cleared.
.SH RETURN VALUE
.LP
Upon successful completion, \fItruncate\fP() shall return 0. Otherwise,
-1 shall be returned, and \fIerrno\fP set to indicate
the error.
.SH ERRORS
.LP
The \fItruncate\fP() function shall fail if:
.TP 7
.B EINTR
A signal was caught during execution.
.TP 7
.B EINVAL
The \fIlength\fP argument was less than 0.
.TP 7
.B EFBIG \fRor\fP EINVAL
The \fIlength\fP argument was greater than the maximum file size.
.TP 7
.B EIO
An I/O error occurred while reading from or writing to a file system.
.TP 7
.B EACCES
A component of the path prefix denies search permission, or write
permission is denied on the file.
.TP 7
.B EISDIR
The named file is a directory.
.TP 7
.B ELOOP
A loop exists in symbolic links encountered during resolution of the
\fIpath\fP argument.
.TP 7
.B ENAMETOOLONG
The length of the \fIpath\fP argument exceeds {PATH_MAX} or a pathname
component is longer than {NAME_MAX}.
.TP 7
.B ENOENT
A component of \fIpath\fP does not name an existing file or \fIpath\fP
is an empty string.
.TP 7
.B ENOTDIR
A component of the path prefix of \fIpath\fP is not a directory.
.TP 7
.B EROFS
The named file resides on a read-only file system.
.sp
.LP
The \fItruncate\fP() function may fail if:
.TP 7
.B ELOOP
More than {SYMLOOP_MAX} symbolic links were encountered during resolution
of the \fIpath\fP argument.
.TP 7
.B ENAMETOOLONG
Pathname resolution of a symbolic link produced an intermediate result
whose length exceeds {PATH_MAX}.
.sp
.LP
\fIThe following sections are informative.\fP
.SH EXAMPLES
.LP
None.
.SH APPLICATION USAGE
.LP
None.
.SH RATIONALE
.LP
None.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fIopen\fP(), the Base Definitions volume of IEEE\ Std\ 1003.1-2001,
\fI<unistd.h>\fP
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version 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 .