Release Notes

busybox-w32 version FRP-4716-g31467ddfc was released on 2022-06-09. It is the current release. For other release notes see:

• the release before this one
• index of all release notes

Junctions

A junction is a Windows filesystem object similar to a symbolic link. There are differences:

• Elevated privileges are not required to create a junction.
• The target of a junction must be a directory on a local drive.

This release adds the jn applet to create junctions:

    $ mkdir directory
    $ jn directory junction
    $ su
    # ln -s directory symlink
    # ls -l 
    total 8
    drwxrwxr-x  2 rmy   rmy    0 Jun 09 13:12 directory
    lrwxrwxrwx  2 rmy   rmy   22 Jun 09 13:12 junction -> C:/Users/rmy/directory
    lrwxrwxrwx  2 root  root   9 Jun 09 13:12 symlink -> directory

Note:

• Although the jn command used a relative path for the target directory, the junction actually contains an absolute path. This may be a problem if the tree containing the junction is moved to a different place.
• The junction and the symbolic link are displayed in the same way by ls. Since Unix has no concept of junctions most applets in busybox-w32 treat them as symbolic links. tar, for example, will store a junction as a symbolic link.

  To distinguish between a junction and a symbolic link use lsattr:

      $ lsattr -d directory symlink junction
      ----------- directory
      l---------- symlink
      j---------- junction
  

(GitHub issue #251)

Overriding applets

Default builds of busybox-w32 prefer applets over external binaries. This allows the shell to do much useful work without requiring any installation beyond just downloading the binary.

Sometimes it may be desirable to replace an applet with a different, external program. The new environment variable BB_OVERRIDE_APPLETS lets the user control which applets are given preference. It may take the following values:

• a single dash ('-') overrides all applets;
• a space-separated list of names overrides only the specified applets.

If an applet is overridden in this way any attempt to run it will cause a PATH lookup.

Suppose, for example, a user is irritated that BusyBox expand interferes with a workflow requiring frequent use of Windows' expand. They can do:

~ $ expand /dev/null
~ $ echo "expletive deleted" >/dev/null
~ $ export BB_OVERRIDE_APPLETS=expand
~ $ expand /dev/null
Microsoft (R) File Expansion Utility  Version 6.1.7600.16385
Copyright (c) Microsoft Corporation. All rights reserved.

No files specified.
~ $

File metadata

As has been noted elsewhere, the details ls displays about files are largely fictional, designed mostly to give long-time Unix users a comfortable feeling of familiarity.

This release makes some further adjustments:

• Write permissions for group/other reflect the current umask setting.
• The link count for directories includes the number of subdirectories they contain. (GitHub issue #254)
• The size reported for a symbolic link or junction more closely represents its actual content.

Reporting on commands

Normally the which applet and shell built-in command -v report the full path of a binary. In standalone shell mode, however, there may not be a binary with a name that matches the command. It would be wrong for which or command to fail in these circumstances so they report just the command name.

This release has the following enhancements:

• If the requested command name matches that of the currently running binary the full path is reported.
• When which is run directly from a shell it will report any applets it finds. To force it to look up a command on PATH it can be run indirectly, for example as env which expand.

Bug fixes and enhancements

• When a login shell is started (with the -l option) the current directory and HOME environment variable are usually set to Windows' idea of the user's home directory. It's now possible to override this by setting HOME before invoking a login shell. (GitHub issue #244)
• The date applet supports the %N format specifier to display times with nanosecond precision.
• A change in the previous release caused environment variables that should have been empty to have the value 0 in certain circumstances. This has been fixed. (GitHub issue #250)
• Release FRP-3578 made it possible for applets to be run using Unix-style executable paths. This feature has been extended so it also applies to binaries in PATH. For example, if curl.exe has been installed to a directory in PATH a shell script referring to /usr/bin/curl will work as expected.

Changes imported from upstream

busybox-w32 has been synchronised with upstream BusyBox.

• There is a new tsort applet which performs a topological sort. It takes pairs of items as input, where the first of each pair is required to appear before the second, and outputs an ordered list consistent with the specified partial ordering:

  $ tsort <<EOF
  > 1 2
  > 2 6 
  > 4 6
  > EOF
  1
  4
  2
  6