lmemsm

While I have other lists that cover a variety topics, wanted one that just had useful lightweight C programs, utilities and libraries. So, I'll be repeating some links here. However, I hope to add some new projects as well. I'd also be interested in hearing suggestions that fit the criteria of lightweight, cross-platform C projects. If you're aware of any I've left off this list, please let me know.

bard
Ebook reader with text-to-speech support using SDL and flite. I have some patches for this program to improve portability and support using SDL2.
https://github.com/festvox/bard

BearSSL
Rather secure implementation of the SSL/TLS protocol. Can be used with curl.
https://bearssl.org/

cal
Command line calendar.
http://unicorn.us.com/cal.html

cDetect
C based alternative to GNU configure/autoconf. More info at IngwiePhoenix's cDetect project ( https://github.com/IngwiePhoenix/cDetect ). Plus, I've forked the project and use it with many of my builds from source code. I've added support for cross-compiling and many, many other features. Contact me if you'd like a copy.
http://cdetect.sourceforge.net/

csvutils
CSV command utilities. Uses libcsv.
https://github.com/rgamble/csvutils

curl
Command line data transfer tool.
https://curl.se/

diction and style
Analyze documents for readability and other metrics. Find grammatical issues.
https://www.gnu.org/software/diction/

diff
diff implementation for sbase. Check the follow-up mailing list threads for further patches.
https://lists.suckless.org/dev/1601/28247.html

diffh
Works with diff and creates an easy to read display of differences between files.
https://sourceforge.net/projects/diffh/

dr_libs
Single file header audio decoding libraries.
https://github.com/mackron/dr_libs

easylzma
Public domain compression and extraction library for lzma.
https://github.com/lloyd/easylzma/tree/master

fcurl
Library to simplify working with curl.
https://github.com/curl/fcurl

BSD gettext
Older BSD gettext/libintl implementation. I have a fork of this one as well. Also, check out the BSD Citrus Project.
https://www.mmnt.net/db/0/18/ftp.khstu.ru/pub/unix/distfiles

gifsicle
GIF animator utility.
http://www.lcdf.org/gifsicle/

grafx2
Graphics editor.
http://grafx2.chez.com/

BSD gzip
BSD version of the gzip compression/decompression program. There are various forks to port this to operating systems other than BSD. I have a portable fork as well.
https://github.com/NetBSD/src/tree/trunk/usr.bin/gzip

less
Less is more than more, pager program.
https://www.greenwoodsoftware.com/less/

libcsv
ANSI C library to read and write CSV files.
https://github.com/rgamble/libcsv

libgrapheme
C99 Unicode library including encoding, decoding and line-break functionality.
https://libs.suckless.org/libgrapheme/

liblzw
Library for LZW (.Z) compression/decompression.
http://freestdf.sourceforge.net/liblzw.php

libtomcrypt
Public Domain cryptography library.
https://github.com/libtom/libtomcrypt

libutf
C89 UTF-8 library which includes an API compatible with Plan 9's libutf plus a number of improvements.
https://github.com/cls/libutf

lxsplit
Command line file split/join tool.
http://lxsplit.sourceforge.net/

man
C program to view standard man pages. Now part of Elks (elkscmd/sys_utils).
https://github.com/jbruchon/elks/blob/1b6110b73fbb123021a5a29b05d8fa9caef33235/elkscmd/sys_utils/man.c
https://github.com/rofl0r/hardcore-utils/blob/master/man.c

mandoc
BSD version of man page utilities. Uses their manpage format. Includes tools to convert to manpage format used by most man tools.
http://mandoc.bsd.lv/
https://embedeo.org/ws/doc/man_windows/

minicpio
Mini cpio compression and decompression routines.
https://github.com/rayae/minicpio

minizip library
A zip library for zlib. Useful when working with files in zip format. Code is in the contrib section of zlib.
http://zlib.net/

nanosvg
Lightweight SVG library.
https://github.com/memononen/nanosvg

ncurses hexedit
Curses based hex editor.
http://www.rogoyski.com/adam/programs/hexedit/

nemini
Lightweight SDL2 based Gemini client.
https://github.com/neonmoe/nemini

BSD patch
BSD fork of the patch program. I have a fork of this as well with some portability additions to better handle carriage return/line feed issues.
https://github.com/openbsd/src/tree/master/usr.bin/patch

pdfconcat
Concatenates PDF files.
https://github.com/pts/pdfconcat

pdftxt
Convert PDF to text. Helpful for searching PDFs with grep.
https://litcave.rudi.ir/

pdlzip
Compression/decompression for lzma format compatible with the lzip data compressor.
https://www.nongnu.org/lzip/pdlzip.html

picaxo
Graphics viewer.
http://gigi.nullneuron.net/comp/picaxo/

pkgconf
Drop in replacement for pkg-config with no circular dependencies.
https://github.com/pkgconf/pkgconf

pspg
Postgres pager provides a console based pager for PostgreSQL, MySQL, CSV and other formats. Uses ncurses (or pdcurses).
https://github.com/okbob/pspg

sbase
Efficient implementations of core base utilities.
https://core.suckless.org/sbase/

shot
Command line screenshot program.
https://github.com/rr-/shot/

sox
Sound exchange utility. Converts sound formats. Plays audio files.
http://sox.sourceforge.net/

stb
Public Domain single file header libraries. Includes stb_truetype.h, a lightweight alternative to the freetype library, which can parse, decode and rasterize characters from truetype fonts.
https://github.com/nothings/stb

TinyLZMA
Minimal LZMA compressor and decompressor.
https://github.com/WangXuan95/TinyLZMA

unarr
Decompression library for rar and other formats. Part of sumatrapdf project.
https://github.com/sumatrapdfreader/sumatrapdf/tree/master/ext/unarr
Standalone version of unarr.
https://github.com/selmf/unarr

x509cert
Generate x509 certificate requests. Works with BearSSL.
https://github.com/michaelforney/x509cert

I have not had much luck in finding places to discuss lightweight, portable software alternatives with other FLOSS enthusiasts. If you have any recommendations on best places to do this, please let me know: http://www.distasis.com/connect.htm

I have been able to find lists with recommendations of alternative software. I've contributed to many of them. If you're looking for lightweight options or alternatives to your current FLOSS software, feel free to check out the following resources.

I have my own list of Open Source software alternatives at: http://www.distasis.com/cpp/osrclist.htm
It lists alternatives to common commercial software as well as programs that can perform a specific function. I haven't limited the list to only lightweight software. However, if I know of lightweight alternatives that I like, they've been included.

I started and contributed to the following lists of software:
https://web.archive.org/web/20200226082503/http://www.mingw.org/wiki/Community_Supplied_Links
https://wiki.musl-libc.org/alternatives.html
However, I no longer have access to those wikis and will no longer be keeping them up-to-date. Check my Converting to Open Source list or this blog for information that I'm actively maintaining.

Some other good places to look for lists of alternative software are with the suckless.org and Plan 9 projects.
For one such list, see https://suckless.org/rocks/
You can find some of the source code:
https://git.suckless.org/

There was a discussion of unbloated coding resources on the Puppy Linux forum:
http://murga-linux.com/puppy/viewtopic.php?t=72359
There's also a related blog article:
http://bashismal.blogspot.com/2011/10/unbloated-resources-in-c.html

The K.Mandla and Inconsolation blogs (both written by the same author) are a great resource for lightweight and alternative software.
For some highlights, see https://kmandla.wordpress.com/software/

There are lots of resource lists on GitHub. I finally ran across one that was partially applicable to lightweight alternative programs. I don't agree with their groupings of which programs may be more minimal than others. However, there are some interesting programs listed including some that I typically haven't seen mentioned anywhere else:
https://github.com/xxzozaxx/guides/blob/master/ALTERNATIVES.md

That's all I've been able to find as far as alternative software lists for lightweight and/or cross-platform software. If you know of any other similar lists you'd like to see added to this reference, please contact me.

It's fun to discover new lightweight applications. They work well on newer computer systems as well as older or slower computers and low resource machines like many mobile devices. You can run more of them at once. If they're not well-known, they can actually be more secure sometimes (using the security through obscurity principle). I also personally prefer portable applications. That way, you can use the same programs on any operating system. You don't have to relearn new programs for each system you work with.

It can be quite a challenge to find new lightweight applications. I've read several threads on forums where users post their favorite lightweight applications. Many truly are not lightweight by standards that take into consideration memory usage, lines of code, compilation time and/or number of dependencies (libraries).

One way to find lightweight applications is to look for programs built with lightweight GUIs. I've seen a few comparisons of GUI performance. This one is particularly good because it tests the various GUIs and gives statistics:
https://www.pismotek.com/brainout/content/gui-toolkit-resources.php
I was rather surprised by the SDL2 results. Generally, the time it takes to build a GUI from source is one good indication of complexity. FLTK and SDL both build quickly from source compared to the other GUI frameworks mentioned. So, I was surprised that SDL2 scored so badly on the memory usage tests. I'd be curious to know if SDL 1.2.x (which many systems still use) would show a large improvement. Another surprise was how well Tcl/Tk did in the tests. I typically think interpreted languages have worse performance than compiled ones. It would be interesting to see some statistics on response times for similar applications created with these GUIs.

I often go through various source repositories such as Sourceforge, github, etc. looking for code written using specific user interfaces in order to find new and interesting applications. Standard search engines are another way to search for programs. The user interfaces I'm personally most interested in at this point are FLTK, pdcurses/ncurses, SDL and command line programs. These types of applications are typically more lightweight or designed to do one thing well. Know of any other lightweight GUIs or TUIs (text user interfaces)? Please share your recommendations and why you like them.

There are some nice blogs for finding and discussing minimalistic (or in some cases maximalistic) programs. Unfortunately, many are no longer very active. Some favorites are:
https://kmandla.wordpress.com/
https://inconsolation.wordpress.com/
https://web.archive.org/web/20160304000554/http://www.jaredandcoralee.com/CLIapps.html
http://macrofig.blogspot.com/

If you know of others, I'd love to hear about them.

One can also look for lightweight distributions and see what programs they have in their repositories or read their forums for more suggestions. Some of the interesting distributions to check are TinyCore Linux (uses several FLTK programs), Nanolinux (uses more interesting FLTK programs), Rogue Class Linux (uses several SDL programs), Puppy Linux, AntiX (Debian based), INX ( http://inx.maincontent.net/ ), Absolute Linux (Slackware based), 4MLinux ( https://sourceforge.net/projects/linux4m/ ), OLPC. Typically DSL and Puppy get mentioned when people list lightweight Open Source systems. There's been no active development on DSL in a long time and the forums are very quiet. I also found Puppy a little too resource intensive on one of my older machines. FreeBSD performed much better on that system. Puppy Linux has some interesting discussions in their forums.

Linux systems that work in framebuffer mode using DirectFB, nano-x and other alternatives also typically contain many interesting, unusual and lightweight applications. Nanolinux and Rogue Class Linux are in this category.

One can also look at operating systems and development projects that use more lightweight C libraries (such as uclibc and musl). Those projects typically gravitate to choosing lightweight applications, command line and console based programs and lightweight tools like Busybox and Toybox.

Alternative operating systems often offer interesting lightweight application choices. Syllable and Haiku often use SDL programs and other lightweight applications that are easier to port to those systems. Systems like Minix and ELKS are also interesting to investigate. Minix 3 uses a lot of the programs that BSD systems do, but earlier versions of Minix include some interesting alternatives. XFDOS includes many interesting FLTK applications. Plan 9 is interesting as well, but not many of the programs used on this system have been ported to other systems. Another good place to look for unusual applications is on mobile devices.
Here are some application lists from Syllable and Agenda:
https://sites.google.com/site/syllablesoftware/
http://agtoys.sourceforge.net/

I'd love to find more places to discuss lightweight applications. If you've written an article on the topic, please share it. If you know of a good blog, forum, mailing list or other resource, please let me know ( http://www.distasis.com/connect.htm ). If you'd like to discuss your favorite C/C++ applications further, you're welcome to check out the mailing list: https://groups.io/g/distasis I had a mailing list on Yahoo Groups called CppDesign, but Yahoo is no longer supporting mailing lists. So, the new list on Groups.io replaces my old lists on Yahoo Groups.

I covered SDL based applications. Now, I'd like to cover FLTK based applications for desktops and/or productivity.

While there isn't as much FLTK application development going on as I would like, there are some projects that specialize in using FLTK. TinyCore Linux is probably the most well-known Linux project that uses several FLTK applications. Nanolinux is based on TinyCore but uses nano-x as a lightweight alternative to X Windows. The developer of NanoLinux uses mainly FLTK applications and has modified and updated several FLTK applications to give them new life. He's also created some of his own where good alternatives did not exist. The Equinox Desktop Environment also uses FLTK, but it typically requires another EDE specific library along with FLTK support. Also, EDE users don't always look for FLTK applications for their desktops. Some will typically use anything they consider lightweight (whether it really is lightweight or not). A few mobile devices use FLTK as their main GUI. Users of those systems have developed some interesting applications for their devices.

There are several versions of FLTK. Applications may work with one version and not another. I've spent a lot of time searching for applications and porting applications to the latest version. I did try to update the FLTK software links list at the official FLTK web site with information on what worked with the latest version of FLTK and with information on newer FLTK applications, but was unable to add some of the newer, more interesting FLTK applications out there. So, this is my definitive list at this point in time of the best FLTK applications available. For more information on FLTK and applications, see also http://www.distasis.com/cpp/scrlib.htm#fltk

I'm sure I haven't covered everything and as mentioned, check NanoLinux and Tiny Core Linux for more FLTK based applications. I'm always looking for new, portable, lightweight FLTK based applications. If you know of something I may have missed or you're working on a new FLTK based project, please contact me.

Utilities

xdiskusage
Shows disk usage. Works on POSIX systems with du command. I have patches to port this to Windows.
http://xdiskusage.sourceforge.net/

flcalc
Calculator. The FLTK web site link includes information on some of my patches to get it to build successfully as well as link to the original source code.
https://www.fltk.org/links.php?V47+Qflcalc

fldiff
Graphical diff program.
https://www.fltk.org/links.php?V227+Qfldiff

xRecurseDiff
Traverse directories and find file differences. Some of it was based on fldiff.
https://sourceforge.net/projects/xrecursediff/

fpwdman
Password manager. I ported this to work with the latest versions of FLTK and tinyxml2. It's interesting, but at this point, I'd prefer a Keepass compatible password manager. I'm looking into chkpass as a lightweight alternative for password management.
https://sourceforge.net/projects/fpwdman/

Communications

prozgui for prozilla
Fast file downloader. I have patches for building and to port this to Windows. I use a version based on GNU GPLv2 development instead of the GNU GPLv3 development.
https://launchpad.net/prozgui

flchat
IRC client. Based on MegaIRC, but with a lot of cleanup. I have patches to add gettext/libintl support. This is the best option for IRC using FLTK that I've found to date.
https://sourceforge.net/projects/nanolinux/

kashyyyk
This has good potential as a threaded IRC client. It can handle multiple connections. I could get it to build on Windows either with patches or a build of MinGW with POSIX instead of Windows native threading support. It needs some work on storing IRC connections. Doesn't seem to remember any connections once you leave the application.
https://sourceforge.net/projects/kashyyyk/?source=directory

Browsers

There are two webkit based browsers for FLTK. That's great news for FLTK applications users. What's not so great is that they don't port well to non-POSIX systems. If you want the most lightweight webkit based browser (and webkit browsers are not by nature lightweight), I'd go with either of these options instead of the many other webkit ports out there.

Netrider
I was able to get the original version of netrider to port to Windows and a Windows version of it is available at Sourceforge. However, when I upgraded the version of my MinGW compiler, I was no longer able to build netrider. Seems the webkit developers took some shortcuts in the older code that really weren't up to C++ standards. Netrider upgraded to a later version of webkit (which fixed the compiler issue), but the newer version was never ported to Windows.
https://sourceforge.net/projects/netrider/

Fifth
This was never ported to Windows although it might be easier to port that the latest version of Netrider. It uses makefiles created by the developer instead of cmake.
http://fifth-browser.sourceforge.net/

DPlus
When people talk about FLTK based web browsers, Dillo always comes up. However, Dillo is the opposite of what I think of when I think about portable code. One developer decided to fork Dillo and make it more structured and easier to port. He's really done a wonderful job on cleaning up the code. I'd recommend this browser over Dillo if you're interested in doing anything with the source code or need a lightweight HTML viewer for FLTK. DPlus is also the lightest browser I could find that could display output from diffh properly. Most console browsers like lynx had trouble rendering the color differences in the output.
https://sourceforge.net/projects/dplus-browser/

DPlusUI
While this is meant as a utility rather than a web browser, I used DPlus as the starting point for my HTML/CSS based dialog replacement.
http://www.distasis.com/cpp/lmbld.htm#lmbldui

Mail clients

flmail
The developer of Nanolinux wrote a nice, basic, stable e-mail client. (He also reused part of my Open Source POP3 e-mail code.)
https://sourceforge.net/projects/nanolinux/

Postoffice
This has a lot of potential. It took a long while to get it to build with the latest version of FLTK and it's still kind of buggy. I also needed to update helper libraries fl_toggletree and fleditor to work with the latest FLTK. The interface is a lot of like sylpheed and foxmail. I would love to see some new development on this and would be happy to help update it.
ftp://linuxmafia.com/faq/Mail/muas.html

hermail
There was a nice, very basic, stable e-mail client at Sourceforge. Doesn't appear to be available from there any longer.

RSS reader
Gautier's RSS reader
This one has a lot of potential. It has an attractive user interface that's easy to work with. However, it does have the ability to sort RSS posts at this point at time. It needs to be used in conjunction with a script and tools like curl to download the RSS feeds. It's basically just a reader. It uses SQLLite to store the RSS data so it can potentially provide fast access to RSS posts. I'd love to see some further development done on this project.
https://michaelgautiertechnology.wordpress.com/2015/10/09/gautier-rss-app-technology/

AV

flvlc
Cross-platform VLC based media player.
https://sourceforge.net/projects/flvlc/

flxine
Unfortunately, this only works on POSIX systems so far. I have been able to build it on Cygwin as well as BSD and several Linux systems. This might be portable to more platforms using nano-x (and possibly SDL as the backend for nano-x), but I did not get very far in investigating this option. It is my favorite xine front end and is more lightweight than many of the other xine front end options. It provides a variety of features including a nice visualization component for use while playing music.
https://www.fltk.org/links.php?V199+Qflxine

Audio

flrec
Simple Audio recorder and player based on Sox. I have done some work to port this one to Windows.
http://matteolucarelli.altervista.org/flrec/index_en.htm

Fl_MIDIKeyboard
Midi keyboard.
https://github.com/ncassetta/Fl_MIDIKeyboard

PaulStretch
Audio effects program to stretch sounds.
http://hypermammut.sourceforge.net/paulstretch/

APCStudio
After more than one try to get this to build with the latest version of FLTK, I finally managed to get this working. It's a nice, lightweight audio editor. It doesn't display multiple tracks like Audacity. It does not have good support for playing or recording wave files. It's basically just a wave file editor. Was considering using libsox or another Open Source sound library to add support for playing wave files.
https://www.fltk.org/links.php?V204+Qapcstudio

There is a fork of FLTK called NTK. It isn't as portable as FLTK and requires POSIX/X Windows support. A suite of audio applications were created with it.

Graphics

Rendera
This is a great, lightweight graphics editor. I really like this one.
https://github.com/Mortis69/rendera
https://sourceforge.net/projects/rendera/

PhotoColoring
Specialized graphics editor for coloring old photos.
https://sourceforge.net/projects/photocoloring/

Other graphics and drawing options include Antipaint and Cinepaint. Antipaint was updated to work with the lastest version of FLTK and to improve portability by the developer of Nanolinux. You'll find it at the Nanolinux web site. At one point Cinepaint decided to port their project from GTK to FLTK. You'll find some older versions with some FLTK support and utilities. However, the FLTK port is not actively developed.

Productivity

fltdj
The Daily Journal is a Personal Information Manager (PIM). It has several nice features including the ability to set alarms to remind you of appointments. I use one of the older versions (0.7) which ports well to newer versions of FLTK and, per my recommendation, so does NanoLinux.
https://www.fltk.org/links.php?V386+Qfltdj

tux_todo
Simple todo list. Haven't used it in a while, but if you're looking for a todo list program, it's an option.
https://www.fltk.org/links.php?V76+Qtux_todo

PDF/Ebook Readers

SpRead
A functional, basic PDF viewer and archived image viewer. I really like this one. It requires a compiler with later C++ support to build. Needs minimal dependencies, mainly libarchive and poppler. While poppler isn't as fast as mupdf at rendering, this still works pretty fast.
https://github.com/muranoya/SpRead

flviewer
Image viewer with plugin support for mupdf and poppler.
https://github.com/madrat-/flviewer

There's also flaxpdf which is optimized for efficiency and uses mupdf. However, it's not at all portable to non-POSIX systems.

I tried BDReader as well but there are a lot of dependencies involved in building this.
https://sourceforge.net/projects/bdreader/

File managers

I don't use any of these and personally prefer the SDL based file manager mentioned earlier. However, they're nice lightweight GUI file managers. I'm sure there are a few others not mentioned below as well.

mfm
http://sg67.altervista.org/mfm/

fluff
https://sites.google.com/site/lockmoorecoding/downloads/fluff

Other POSIX only FLTK applications

flsynclient
GUI front end for synaptics touchpad controls.
http://matteolucarelli.altervista.org/flsynclient/index_en.htm

alsamixergui
FLTK ALSA Mixer front end.
https://packages.debian.org/jessie/alsamixergui

Editors

I've yet to find a FLTK based editor I really like. For now, I'm still using SciTE, Fxite and nano.

I would love to find a Scintilla based FLTK editor. The closest I've found is https://github.com/cyantreeguo/Fl_Scintilla

There are many FLTK editor controls out there, including the one used by Postoffice.

Nanolinux offers flwriter.

The most interesting editor option I've found so far is fldev. There's a link to the original at https://www.fltk.org/links.php?V235+Qfldev and further development by the developer of NanoLinux at https://sourceforge.net/projects/fldev/ The main drawback is that it only opens one file at a time. The original author began to add support to use it as a debugger in conjunction with gdb. I'd love to get that support working properly and in a cross-platform manner and have been experimenting with it as time allows.

flabc is an editor specifically designed for ABC notation, but it appears to be a stable, well-written editor and may be useful for other editing purposes.