Noon van der Silk

Versioned LyX documents

Oftentimes one needs to write a document with math symbols in it. The standard tool of choice is some variant of TeX, either writing it online in one of the growing-list of collaborative editors:

• Overleaf
• ShareLaTeX
• Authorea

But one program, that runs locally, that I can’t stop using is LyX.

I really like LyX because of the “What-you-see-is-(pretty much)-what-you-get” nature of it.

One thing I wanted to share was a small technique that I used to get a version number in all of the pdfs that I generated from my LyX documents. The idea was that when I sent my document to obtain feedback from various interested parties, I could easily see which version they had commented on.

What I wanted as a footer that would be included on every page, that contained the version number.

The approach is:

1. In the “LaTeX Preamble” setting of the LyX document, include (something like)

\usepackage{fancyhdr}
\pagestyle{fancy}
\cfoot{\tiny{|VERSION|}}
\rfoot{\thepage}
\rhead{}

2. Build your LyX documents by the command line with a Makefile. My Makefile looks like so:

BUILD_NUMBER_FILE := build-number.txt
BUILD_NUMBER      := $(shell cat $(BUILD_NUMBER_FILE))
BUILD_DATE        := $(shell date +%d%b%Y)
VER_STRING        := $(BUILD_DATE)-build$(BUILD_NUMBER)
LYXFILE           := coolness
TEMPDIR           := /tmp

all: pdf

# Switch in the new version number, compile with LyX and
# bring it here.
pdf: buildnumber
	sed "s/|VERSION|/$(VER_STRING)/g" $(LYXFILE).lyx >$(TEMPDIR)/$(LYXFILE).lyx
	lyx -e pdf2 $(TEMPDIR)/$(LYXFILE).lyx
	cp $(TEMPDIR)/$(LYXFILE).pdf .

# Build number file. Increment each build.
buildnumber:
	@if ! test -f $(BUILD_NUMBER_FILE); then echo 0 > $(BUILD_NUMBER_FILE); fi
	@echo $$(($$(cat $(BUILD_NUMBER_FILE)) + 1)) > $(BUILD_NUMBER_FILE)

3. Build with the make command and profit!

Note that there is a build-number.txt file that is incremented on each build, so you don’t need to do that manually.

I’ve put together a sample project here, so you can clone that gist and type make and see it in action!