truncate(3C) manual page
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truncate, ftruncate - set a file to a specified length
#include
<unistd.h>
int truncate(const char *path, off_t length);
int ftruncate(int
fildes, off_t length);
MT-Safe
The file whose name
is given by path or referenced by the descriptor fildes has its size set
to length bytes.
If the file was previously longer than length, bytes past
length will no longer be accessible. If it was shorter, bytes from the EOF
before the call to the EOF
after the call will be read in as zeros. The
effective user ID
of the process must have write permission for the file,
and for ftruncate() the file must be open for writing.
Upon
successful completion, a value of 0 is returned. Otherwise, a value of -1
is returned and errno is set to indicate the error.
truncate() fails
if one or more of the following are true:
- EACCES
- Search permission is
denied on a component of the path prefix.
- EACCES
- Write permission is denied
for the file referred to by path.
- EFAULT
- path points outside the process’s
allocated address space.
- EINTR
- A signal was caught during execution of
the truncate routine.
- EINVAL
- path is not an ordinary file.
- EIO
- An I/O
error occurred while reading from or writing to the file system.
- EISDIR
- The file referred to by path is a directory.
- ELOOP
- Too many symbolic links
were encountered in translating path.
- EMFILE
- The maximum number of file
descriptors available to the process has been reached.
- EMULTIHOP
- Components
of path require hopping to multiple remote machines and file system type
does not allow it.
- ENAMETOOLONG
- The length of a path component exceeds
{NAME_MAX} characters, or the length of path exceeds {PATH_MAX} characters.
- ENFILE
- Could not allocate any more space for the system file table.
- ENOENT
- Either a component of the path prefix or the file referred to by path
does not exist.
- ENOLINK
- path points to a remote machine and the link to
that machine is no longer active.
- ENOTDIR
- A component of the path prefix
of path is not a directory.
- EROFS
- The file referred to by path resides
on a read-only file system.
ftruncate() fails if one or more of the following
are true:
- EAGAIN
- The file exists, mandatory file/record locking is set,
and there are outstanding record locks on the file (see chmod(2)
).
- EBADF
- fildes is not a file descriptor open for writing.
- EINTR
- A signal was caught
during execution of the ftruncate routine.
- EIO
- An I/O error occurred while
reading from or writing to the file system.
- ENOLINK
- fildes points to a
remote machine and the link to that machine is no longer active.
- EINVAL
- fildes does not correspond to an ordinary file.
chmod(2)
, fcntl(2)
,
open(2)
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