truncate(), truncate64()
Truncate a file to a specified length
Synopsis:
#include <unistd.h>
int truncate( const char* path,
off_t length );
int truncate64( const char* path,
off64_t length );
Arguments:
- path
- The path name of the file that you want to truncate.
- length
- The new size of the file.
Library:
libc
Use the -l c option to qcc to link against this library. This library is usually included automatically.
Description:
The truncate() and truncate64() functions cause the regular file named by path to have a size of length bytes. The truncate64() function is a large-file support version of truncate().
Classificationin What's in a Function Description?
The effect of truncate() on other types of files is undefined. If the file previously was larger than length, the extra data is lost. If it was previously shorter than length, bytes between the old and new lengths are read as zeroes. The process must have write permission for the file.
This function doesn't modify the file offset for any open file descriptions associated with the file. On successful completion, if the file size is changed, truncate() marks 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 may be cleared.
Returns:
- 0
- Success.
- -1
- An error occurred; errno is set.
Errors:
- EACCES
- A component of the path prefix denies search permission, or write permission is denied on the file.
- EFAULT
- The path argument points outside the process's allocated address space.
- EFBIG
- The length argument was greater than the maximum file size.
- EINTR
- A signal was caught during execution.
- EINVAL
- The length argument is invalid, or the path argument isn't an ordinary file.
- EIO
- An I/O error occurred while reading from or writing to a filesystem.
- EISDIR
- The named file is a directory.
- ELOOP
- Too many symbolic links were encountered in resolving 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 filesystem type doesn't allow it.
- ENAMETOOLONG
- The length of the specified pathname exceeds PATH_MAX bytes.
- ENFILE
- Additional space couldn't be allocated for the system file table.
- ENOENT
- A component of path doesn't name an existing file or path is an empty string.
- ENOLINK
- The path argument points to a remote machine and the link to that machine is no longer active.
- ENOTDIR
- A component of the path prefix of path isn't a directory.
- EROFS
- The named file resides on a read-only filesystem.
Classification:
truncate() is POSIX 1003.1; truncate64() is Large-file support
| Safety: | |
|---|---|
| Cancellation point | No |
| Signal handler | Yes |
| Thread | Yes |