TRUNCATE(3)                POSIX Programmer's Manual               TRUNCATE(3)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

NAME
       truncate -- 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
       discarded. 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,
       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
              resolution 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 ALSO
       open()

       The Base Definitions volume of POSIX.1-2017, <unistd.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       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.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                          TRUNCATE(3)
