truncate.2

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 2 代码 · 共 103 行

.\" SCCSID: @(#)truncate.2	8.1	9/11/90
.TH truncate 2
.SH Name
truncate, ftruncate \- truncate a file to a specified length
.SH Syntax
.nf
.ft B
truncate(path, length)
char *path;
int length;
.PP
.ft B
ftruncate(fd, length)
int fd, length;
.fi
.SH Description
.NXR "truncate system call"
.NXR "ftruncate system call"
.NXR "file" "truncating to specified length"
The
.PN truncate
system call causes the file named by
.I path
or referenced by
.I fd
to be truncated to, at most,
.I length
bytes in size.  If the file previously
was larger than this size, the extra data
is lost.
With
.PN ftruncate ,
the file must be open for writing.
.SH Return Values
A value of zero (0) is returned if the call succeeds.  If the call
fails, a \-1 is returned, and the global variable \fIerrno\fP
specifies the error.
.SH Restrictions
Partial blocks discarded as the result of truncation
are not zero-filled. This can result in holes in files
that do not read as zero.
.SH Diagnostics
The
.PN truncate
system call
succeeds unless:
.TP 15
[ENOTDIR]
A component of the path prefix is not a directory.
.TP 15
[ENOENT]
The named file does not exist.
.TP 15
[EACCES]
Search permission is denied for a component of the path prefix.
.TP 15
[EISDIR]
The named file is a directory.
.TP 15
[EROFS]
The named file resides on a read-only file system.
.TP 15
[ETXTBSY]
The file is a pure procedure (shared text) file that is being executed.
.TP 15
[EFAULT]
The
.I path 
points outside the process's allocated address space.
.TP 15
[ENAMETOOLONG]
A component of a pathname exceeded 255 characters, or an entire
path name exceeded 1023 characters.
.TP 15
[ELOOP]
Too many symbolic links were encountered in translating the
pathname.
.TP 15
[EIO]
An I/O error occurred updating the inode.
.PP
The
.PN ftruncate
system call succeeds unless:
.TP 15
[EBADF]
The
.I fd
is not a valid descriptor.
.TP 15
[EINVAL]
The
.I fd
references a socket, not a file.
.TP
[ETIMEDOUT]
A connect request or remote file operation failed,
because the connected party
did not properly respond after a period
of time that is dependent on the communications protocol.
.SH See Also
open(2)