An implementation of the Unix ls utility for CP/M.
Version 0.1b, February 2022
cpm-ls is a file lister for CP/M (Z80 or 8080) broadly similar to the Linux
ls utility. There are many such implementations for CP/M; I've tried here
to make a reasonably fully-featured one that fits into less than 10kB. In
particular, though, I've tried to implement something that can, if necessary,
be maintained on a CP/M system, using original CP/M tools, not just
cross-compiled on a modern workstation.
This implementation is, of course, much simpler than the Linux one, because CP/M stores only a rudimentary set of information about a file, and does not support directories.
Features:
- Sorts files in a variety of ways
- Wide listing fits to width
- Long listing shows file attributes and sizes
- Supports Unix-style and CP/M-style command-line switches
ls [options] [drive:pattern] [drive:pattern]...
Options can be specified using the '/' or '-' characters.
-b In 'long' format, display file size in CP/M blocks rather than bytes/kilobytes
-l Display in long format, one file to a line, including file attributes and size. Attributes are displayed like this:
[RSA]
where R=read-only, S=system, A=archive.
-p Display a page at a time. After each page, hit 'enter' to advance by one line, 'space' to advance by a page, or ctrl-c to exit.
-r Sort in the opposite order to the default (i.e., reverse alphabetic order).
-s Sort by size.
-u Unsorted -- do not sort at all.
-x Sort by file extension.
The drive/pattern specification can contain wildcards (see below), such as "b:*.com". By default, files are sorted in alphabetic order of name. If no drive letter is given, the current logged-in drive is assumed.
- and ? can be used as wildcards. Patterns are not as flexible as on Linux.
*.com matches anything that has the extension com.
c*.com matches anything that begins with c, and has the extension com.
*c.com is treated the same as *.com
* matches anything without an extension (as in MSDOS).
Unlike in Unix/Linux, the extension in CP/M is a first-class part of
a file, not just something following a period.
*.* matches everything, with or without extension. Specifying this as a
pattern is equivalent to not specifying anything.
This utility will build on CP/M using the Manx Aztec C compiler, version 1.06d. It will also build on Linux, using a CP/M emulator and the same compiler. See the Makefile for where to get the necessary bits.
Building on CP/M amounts to compiling all the C files, assembling all the ASM files, and then linking all the resulting object files. On Linux, use the Makefile, which automates these steps.
cpm-ls is written in a mixture of C and assembly language. The assembly
parts are simple -- they just do console I/O. Doing these things in assembly
prevents the linker incorporating all the buffered I/O stuf from the standard
library, reducing the code size by about 6k (that doesn't sound much, but
it's about 30%).
In order to sort files, their names and some attributes must first be read into memory -- CP/M provides no help for this. This means that the utility can potentially use a lot of memory. Even if unsorted operation is not specified, it might still be necessary to read the files into memory. For example, to find the longest filename (for the purposes of fitting to the screen), it's actually quicker to read the filenames into memory, than to iterate them twice.
This implementation detail does create a limitation (see below) on the number of files that can be displayed.
I chose the Aztec C compiler for this utility, because it generates Z80-compatible 8080 code. I suspect that a Z80-specific compiler would produce smaller code, that might be a little faster.
By default, cpm-ls lists a maximum of 256 files, allowing it to run on
a system with 16kB RAM without much memory checking.
Sorting files, particular by name, can be slow on low-powered systems (and "low-powered" really means something in the CP/M world).
File sizes are display in kB when larger than 1 kB. This is not just for neatness, but to avoid any need for arithmetic of more than 16-bit range (which would make the program significantly larger).
Copyright (c)2022-3 Kevin Boone, and released under the terms of the GNU Public Licence v3.0.
0.1b May 2023 :
- Fixed a horrible bug in memory management
- Fixed a bug that caused file attributes not to display
- Fixed a bug that caused some file sizes to display wrongly as zero