Ad Hoc Protocols in Unix

Related: Unix Tools

Data / "microformats"

• shebang lines: recognized by the kernel
• gF in Vim recognizes filename and line number!
• /* vim */ options
• yacc, in y.tab.c output:
  • #line 407 "/usr/homes/chet/src/bash/src/parse.y" /* yacc.c:1646 */
  • this appears to be recognized by code coverage reporting tools? They show parse.y output.
    • This actually affects the C compiler's idea of "current file and line". It affects error messages from C compiler, and debug info that goes into/alongside the executable. Code coverage tools probably read the debug info. I think it was invented as an internal protocol between C preprocessor -> C compiler, but proved useful for public use by code generation tools like yacc...
• various "text files" in /proc on Linux

Code over Pipes

• eval "$(ssh-agent)"
• gcc -M sends a Makefile fragment