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-rw-r--r--lib/libc/sys/truncate.226
1 files changed, 19 insertions, 7 deletions
diff --git a/lib/libc/sys/truncate.2 b/lib/libc/sys/truncate.2
index f06c1eb..0734464 100644
--- a/lib/libc/sys/truncate.2
+++ b/lib/libc/sys/truncate.2
@@ -28,7 +28,7 @@
.\" @(#)truncate.2 8.1 (Berkeley) 6/4/93
.\" $FreeBSD$
.\"
-.Dd December 13, 2006
+.Dd May 4, 2015
.Dt TRUNCATE 2
.Os
.Sh NAME
@@ -60,9 +60,18 @@ is lost.
If the file was smaller than this size,
it will be extended as if by writing bytes
with the value zero.
-With
-.Fn ftruncate ,
-the file must be open for writing.
+.Pp
+The
+.Fn ftruncate
+system call causes the file or shared memory object backing the file descriptor
+.Fa fd
+to be truncated or extended to
+.Fa length
+bytes in size.
+The file descriptor must be a valid file descriptor open for writing.
+The file position pointer associated with the file descriptor
+.Fa fd
+will not be modified.
.Sh RETURN VALUES
.Rv -std
If the file to be modified is not a directory or
@@ -129,7 +138,7 @@ is not a valid descriptor.
The
.Fa fd
argument
-references a socket, not a file.
+references a file descriptor that is not a regular file or shared memory object.
.It Bq Er EINVAL
The
.Fa fd
@@ -138,11 +147,14 @@ is not open for writing.
.El
.Sh SEE ALSO
.Xr chflags 2 ,
-.Xr open 2
+.Xr open 2 ,
+.Xr shm_open 2
.Sh HISTORY
The
.Fn truncate
-system call appeared in
+and
+.Fn ftruncate
+system calls appeared in
.Bx 4.2 .
.Sh BUGS
These calls should be generalized to allow ranges
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