|TRUNCATE(3C)||Standard C Library Functions||TRUNCATE(3C)|
#include <unistd.h> int truncate(const char *path, off_t length);
int ftruncate(int fildes, off_t length);
The truncate() function causes the regular file named by path to have a size 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 must ensure that the process has write permission for the file.
This function does not modify the file offset for any open file descriptions associated with the file.
The ftruncate() function causes the regular file referenced by fildes to be truncated to length. If the size of the file previously exceeded length, the extra data is no longer available to reads on the file. If the file previously was smaller than this size, ftruncate() increases the size of the file with the extended area appearing as if it were zero-filled. The value of the seek pointer is not modified by a call to ftruncate().
The ftruncate() function works only with regular files and shared memory. If fildes refers to a shared memory object, ftruncate() sets the size of the shared memory object to length. If fildes refers to a directory or is not a valid file descriptor open for writing, ftruncate() fails.
If the effect of ftruncate() is to decrease the size of a shared memory object or memory mapped file and whole pages beyond the new end were previously mapped, then the whole pages beyond the new end shall be discarded.
If the effect of ftruncate() is to increase the size of a shared memory object, it is unspecified if the contents of any mapped pages between the old end-of-file and the new are flushed to the underlying object.
These functions do not modify the file offset for any open file descriptions associated with the file. On successful completion, if the file size is changed, these functions will mark for update the st_ctime and st_mtime fields of the file, and if the file is a regular file, the S_ISUID and S_ISGID bits of the file mode are left unchanged.
If the request would cause the file size to exceed the soft file size limit for the process, the request will fail and a SIGXFSZ signal will be generated for the process.
Upon successful completion, ftruncate() and truncate() return 0. Otherwise, −1 is returned and errno is set to indicate the error.
The ftruncate() and truncate() functions will fail if:
EFBIG or EINVAL
The truncate() function will fail if:
The ftruncate() function will fail if:
EBADF or EINVAL
The truncate() function may fail if:
The truncate() and ftruncate() functions have transitional interfaces for 64-bit file offsets. See lf64(7).
See attributes(7) for descriptions of the following attributes:
|ATTRIBUTE TYPE||ATTRIBUTE VALUE|
|April 5, 2002||OmniOS|