TRUNCATE(3P) POSIX Programmer's Manual TRUNCATE(3P)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.
NAMEtruncate — truncate a file to a specified length
SYNOPSIS
#include <unistd.h>
int truncate(const char *path, off_t length);
DESCRIPTION
The truncate() function shall cause the regular file named by path to
have a size which shall be equal to length bytes.
If the file previously was larger than length, the extra data is dis‐
carded. If the file was previously shorter than length, its size is
increased, and the extended area appears as if it were zero-filled.
The application shall ensure that the process has write permission for
the file.
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.
The truncate() 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, truncate() shall mark for update the last
data modification and last file status change timestamps of the file,
and the S_ISUID and S_ISGID bits of the file mode may be cleared.
RETURN VALUE
Upon successful completion, truncate() shall return 0. Otherwise, −1
shall be returned, and errno set to indicate the error.
ERRORS
The truncate() function shall fail if:
EINTR A signal was caught during execution.
EINVAL The length argument was less than 0.
EFBIG or EINVAL
The length argument was greater than the maximum file size.
EIO An I/O error occurred while reading from or writing to a file
system.
EACCES A component of the path prefix denies search permission, or
write permission is denied on the file.
EISDIR The named file is a directory.
ELOOP A loop exists in symbolic links encountered during resolution of
the path argument.
ENAMETOOLONG
The length of a component of a pathname is longer than
{NAME_MAX}.
ENOENT A component of path does not name an existing file or path is an
empty string.
ENOTDIR
A component of the path prefix names an existing file that is
neither a directory nor a symbolic link to a directory, or the
path argument contains at least one non-<slash> character and
ends with one or more trailing <slash> characters and the last
pathname component names an existing file that is neither a
directory nor a symbolic link to a directory.
EROFS The named file resides on a read-only file system.
The truncate() function may fail if:
ELOOP More than {SYMLOOP_MAX} symbolic links were encountered during
resolution of the path argument.
ENAMETOOLONG
The length of a pathname exceeds {PATH_MAX}, or pathname resolu‐
tion of a symbolic link produced an intermediate result with a
length that exceeds {PATH_MAX}.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
None.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSOopen()
The Base Definitions volume of POSIX.1‐2008, <unistd.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the source
files to man page format. To report such errors, see https://www.ker‐
nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 TRUNCATE(3P)
