TRUNCATE(E)         Linux Programmer's Manual         TRUNCATE(E)



NAME
       truncate,  ftruncate  -  truncate  a  file  to a specified
       length

SYNOPSIS
       #include <unistd.h>

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

DESCRIPTION
       The truncate and ftruncate  functions  cause  the  regular
       file  named by path or referenced by fd to be truncated to
       a size of precisely length bytes.

       If the file previously was  larger  than  this  size,  the
       extra  data  is lost.  If the file previously was shorter,
       it is extended, and the extended part reads as zero bytes.

       The file pointer is not changed.

       With  ftruncate,  the  file must be open for writing; with
       truncate, the file must be writable.

RETURN VALUE
       On success, zero is returned.  On error, -1  is  returned,
       and errno is set appropriately.

ERRORS
       For truncate:

       EACCES Search  permission is denied for a component of the
              path prefix, or the named file is not  writable  by
              the user.

       EFAULT Path points outside the process's allocated address
              space.

       EFBIG  The argument length is larger than the maximum file
              size. (XSI)

       EINTR  A signal was caught during execution.

       EINVAL The  argument length is negative or larger than the
              maximum file size.

       EIO    An I/O error occurred updating the inode.

       EISDIR The named file is a directory.

       ELOOP  Too many symbolic links were encountered in  trans-
              lating the pathname.

       ENAMETOOLONG
              A  component of a pathname exceeded 255 characters,
              or an entire path name exceeded 1023 characters.

       ENOENT The named file does not exist.

       ENOTDIR
              A component of the path prefix is not a  directory.

       EROFS  The  named file resides on a read-only file system.

       ETXTBSY
              The file is a pure  procedure  (shared  text)  file
              that is being executed.

       For ftruncate the same errors apply, but instead of things
       that can be wrong with path, we now have things  that  can
       be wrong with fd:

       EBADF  The fd is not a valid descriptor.

       EBADF or EINVAL
              The fd is not open for writing.

       EINVAL The fd does not reference a regular file.

CONFORMING TO
       4.4BSD,  SVr4  (these function calls first appeared in BSD
       4.2).  POSIX 1003.1-1996 has ftruncate.  POSIX 1003.1-2001
       also has truncate, as an XSI extension.

       SVr4   documents   additional  truncate  error  conditions
       EMFILE, EMULTIHP, ENFILE,  ENOLINK.   SVr4  documents  for
       ftruncate an additional EAGAIN error condition.

NOTES
       The  above  description is for XSI-compliant systems.  For
       non-XSI-compliant systems, the POSIX standard  allows  two
       behaviours  for  ftruncate  when  length  exceeds the file
       length (note that truncate is not specified at all in such
       an  environment):  either returning an error, or extending
       the file.  (Most Unices follow the XSI requirement.)

SEE ALSO
       open(n)



                            1998-12-21                TRUNCATE(E)