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.

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 .