Originální popis anglicky:
truncate - truncate a file to a specified length
Návod, kniha: POSIX Programmer's Manual
#include <unistd.h>
int truncate(const char *
path, off_t
length );
The
truncate() function shall cause the regular file named by
path
to have a size which shall be 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 shall ensure that the process has write permission for the file.
If the request would cause the file size to exceed the soft file size limit for
the process, the request shall fail and the implementation shall generate the
SIGXFSZ signal for the process.
This function shall not modify the file offset for any open file descriptions
associated with the file. Upon successful completion, if the file size is
changed, this function shall mark for update the
st_ctime and
st_mtime fields of the file, and the S_ISUID and S_ISGID bits of the
file mode may be cleared.
Upon successful completion,
truncate() shall return 0. Otherwise, -1
shall be returned, and
errno set to indicate the error.
The
truncate() function shall fail if:
- EINTR
- A signal was caught during execution.
- EINVAL
- The length argument was less than 0.
- EFBIG or EINVAL
- The length argument was greater than the maximum
file size.
- EIO
- An I/O error occurred while reading from or writing to a
file system.
- EACCES
- A component of the path prefix denies search permission, or
write permission is denied on the file.
- EISDIR
- The named file is a directory.
- ELOOP
- A loop exists in symbolic links encountered during
resolution of the path argument.
- ENAMETOOLONG
- The length of the path argument exceeds {PATH_MAX}
or a pathname component is longer than {NAME_MAX}.
- ENOENT
- A component of path does not name an existing file
or path is an empty string.
- ENOTDIR
- A component of the path prefix of path is not a
directory.
- EROFS
- The named file resides on a read-only file system.
The
truncate() function may fail if:
- ELOOP
- More than {SYMLOOP_MAX} symbolic links were encountered
during resolution of the path argument.
- ENAMETOOLONG
- Pathname resolution of a symbolic link produced an
intermediate result whose length exceeds {PATH_MAX}.
The following sections are informative.
None.
None.
None.
None.
open() , the Base Definitions volume of
IEEE Std 1003.1-2001,
<unistd.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html
.
