BSD 4_3 release

[unix-history] / usr / man / man5 / dir.5

diff --git a/usr/man/man5/dir.5 b/usr/man/man5/dir.5
index 47e2890..b762522 100644 (file)
--- a/usr/man/man5/dir.5
+++ b/usr/man/man5/dir.5
@@ -1,4 +1,11 @@
-.TH DIR 5  "15 January 1983"
+.\" Copyright (c) 1983 Regents of the University of California.
+.\" All rights reserved.  The Berkeley software License Agreement
+.\" specifies the terms and conditions for redistribution.
+.\"
+.\"    @(#)dir.5       6.1 (Berkeley) 5/15/85
+.\"
+.TH DIR 5  "May 15, 1985"
+.UC 5

 .SH NAME
 dir \- format of directories
 .SH SYNOPSIS
 .SH NAME
 dir \- format of directories
 .SH SYNOPSIS


@@ -17,11 +24,29 @@ The structure of a directory entry as given in the include file is:
 .PP
 .nf
 /*
 .PP
 .nf
 /*

- * This sets the "page size" for directories.
- * Requirements are DEV_BSIZE <= DIRBLKSIZ <= MINBSIZE with
- * DIRBLKSIZ a power of two.
- * Dennis Ritchie feels that directory pages should be atomic
- * operations to the disk, so we use DEV_BSIZE.
+ * A directory consists of some number of blocks of DIRBLKSIZ
+ * bytes, where DIRBLKSIZ is chosen such that it can be transferred
+ * to disk in a single atomic operation (e.g. 512 bytes on most machines).
+ *
+ * Each DIRBLKSIZ byte block contains some number of directory entry
+ * structures, which are of variable length.  Each directory entry has
+ * a struct direct at the front of it, containing its inode number,
+ * the length of the entry, and the length of the name contained in
+ * the entry.  These are followed by the name padded to a 4 byte boundary
+ * with null bytes.  All names are guaranteed null terminated.
+ * The maximum length of a name in a directory is MAXNAMLEN.
+ *
+ * The macro DIRSIZ(dp) gives the amount of space required to represent
+ * a directory entry.  Free space in a directory is represented by
+ * entries which have dp->d_reclen > DIRSIZ(dp).  All DIRBLKSIZ bytes
+ * in a directory block are claimed by the directory entries.  This
+ * usually results in the last entry in a directory having a large
+ * dp->d_reclen.  When entries are deleted from a directory, the
+ * space is returned to the previous entry in the same directory
+ * block by increasing its dp->d_reclen.  If the first entry of
+ * a directory block is free, then its dp->d_ino is set to 0.
+ * Entries other than the first in a directory do not normally have
+ * dp->d_ino set to 0.

  */
 #ifdef KERNEL
 #define DIRBLKSIZ DEV_BSIZE
  */
 #ifdef KERNEL
 #define DIRBLKSIZ DEV_BSIZE


@@ -29,11 +54,17 @@ The structure of a directory entry as given in the include file is:
 #define        DIRBLKSIZ 512
 #endif
 
 #define        DIRBLKSIZ 512
 #endif
 

+#define MAXNAMLEN 255
+

 /*
 /*

- * This limits the directory name length. Its main constraint
- * is that it appears twice in the user structure. (u. area)
+ * The DIRSIZ macro gives the minimum record length which will hold
+ * the directory entry.  This requires the amount of space in struct direct
+ * without the d_name field, plus enough space for the name with a terminating
+ * null byte (dp->d_namlen+1), rounded up to a 4 byte boundary.

  */
  */

-#define MAXNAMLEN 255
+#undef DIRSIZ
+#define DIRSIZ(dp) \e
+    ((sizeof (struct direct) - (MAXNAMLEN+1)) + (((dp)->d_namlen+1 + 3) &~ 3))

 
 struct direct {
        u_long  d_ino;
 
 struct direct {
        u_long  d_ino;


@@ -53,11 +84,10 @@ struct _dirdesc {
 .RE
 .PP
 By convention, the first two entries in each directory
 .RE
 .PP
 By convention, the first two entries in each directory

-are for `\fB.\fR' and `\fB..\fR'.  The first is an entry for the
+are for `.' and `..'.  The first is an entry for the

 directory itself.  The second is for the parent directory.
 directory itself.  The second is for the parent directory.

-The meaning of `\fB..\fR' is modified for the root directory
-of the master file system
-.RB (\*(lq / \*(rq),
-where `\fB..\fR' has the same meaning as `\fB.\fR'.
+The meaning of `..' is modified for the root directory
+of the master file system (\*(lq/\*(rq),
+where `..' has the same meaning as `.'.

 .SH "SEE ALSO"
 fs(5)
 .SH "SEE ALSO"
 fs(5)