TRUNCATE
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
Truncate
causes the file named by
path
or referenced by
fd
to be truncated to at most
length
bytes in size. If the file previously was larger than this size, the extra
data is lost. With
ftruncate,
the file must be open for writing.
RETURN VALUE
On success, zero is returned. On error, -1 is returned, and
errno
is set appropriately.
ERRORS
For
truncate:
- ENOTDIR
-
A component of the path prefix is not a directory.
- EINVAL
-
The pathname contains a character with the high-order bit set.
- ENAMETOOLONG
-
A component of a pathname exceeded 255 characters,
or an entire path name exceeded 1023 characters.
- ENOENT
-
The named file does not exist.
- EACCES
-
Search permission is denied for a component of the path prefix.
- EACCES
-
The named file is not writable by the user.
- ELOOP
-
Too many symbolic links were encountered in translating the pathname.
- EISDIR
-
The named file is 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.
- EIO
-
An I/O error occurred updating the inode.
- EFAULT
-
Path
points outside the process's allocated address space.
For
ftruncate:
- EBADF
-
The
fd
is not a valid descriptor.
- EINVAL
-
The
fd
references a socket, not a file.
- EINVAL
-
The
fd
is not open for writing.
CONFORMING TO
4.4BSD, SVr4 (these function calls first appeared in BSD 4.2).
SVr4 documents additional
truncate
error conditions EINTR, EMFILE, EMULTIHP, ENAMETOOLONG, ENFILE,
ENOLINK, ENOTDIR. SVr4 documents for
ftruncate
additional EAGAIN and EINTR error conditions.
POSIX has
ftruncate
but not
truncate.
BUGS
These calls should be generalized to allow ranges of bytes in a file to be
discarded.
SEE ALSO
open(2)