This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface

       None.

       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(3POSIX)

       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.

       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}.

       Thefollowingsectionsareinformative.

       None.

       None.

       truncate — truncate a file to a specified length

       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.

       None.

       Upon successful completion, truncate() shall return 0. Otherwise, -1 shall be returned, and errno set  to
       indicate the error.

open()

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

       #include <unistd.h>

       int truncate(const char *path, off_t length);