chem

Process a chem file and view the output

$ chem [path/to/file.chem] | groffer

$ chem [path/to/file.chem] | groff -p -Tps > [output.ps]

$ echo '.cstart\nCH3\nbond\nCH3\n.cend' | chem | groffer

$ chem --version

chem [option...] [--] [filespec...]
chem -h | --help
chem -v | --version

chem is a groff preprocessor for producing chemical structure diagrams. It translates chemical notation into pic language diagrams, which can then be processed by groff for rendering.
The tool is best suited for organic chemistry, supporting bonds, rings, moieties (like CH3, NH3), and strings. Chemical diagrams are enclosed between .cstart and .cend markers.
Example input:

$ .cstart
CH3
bond
CH3
.cend

-h, --help

Display usage message and exit

Display version information and exit

Input file or - for stdin. Without arguments, reads stdin

No library or file inclusion mechanism exists. No shorthand for repetitive structures. The extension mechanism uses pic macros, which can be tricky to implement correctly.
There is no in-line chemistry syntax (like eqn's $...$ construct) and no way to control bond entry points on groups.

The GNU version of chem was written by Bernd Warken, based on documentation of Brian Kernighan's original awk version. The chemical structure diagram language was developed at Bell Labs alongside other troff preprocessors like eqn and pic.

groff(1), pic(1), eqn(1), groffer(1)