make packaging simexec(1) easier

simexec/packaging.md

@@ -0,0 +1,40 @@
+# Packaging simexec.c
+
+## License
+
+Simexec is Public Domain so there are basically no barriers when it comes to
+licensing. And if you somehow violate my already-forfeited copyright, I promise
+I won't sue you.
+
+## Files
+
+Simexec is a single C file (`simexec.c`) that builds to a single executable,
+which should be named `simexec` and placed in a user-accessible binaries
+directory. A `Makefile` is provided as courtesy but isn't really necessary.
+
+The `src/simexec` directory can be moved to a system sources directory if you
+wish to keep the source on hand; it doesn't reference anything else in the
+repository.
+
+The included manual page, `simexec.1` can be placed in the appropriate manual
+pages directory. If it displays weirdly feel free to e-mail me and I'll attempt
+to fix it.
+
+## Compilation
+
+On systems that provide `<sysexits.h>`, the following is all that's needed:
+
+```
+cc -o simexec simexec.c
+```
+
+If you're not sure whether your system provides `<sysexits.h>`, try it and see.
+If it doesn't work, compile `simexec.c` with the following:
+
+```
+cc -DEX_USAGE=1 -o simexec simexec.c
+```
+
+Other than `<sysexits.h>` simexec(1) only relies on headers found in the C
+standard library. Outside of POSIX environments `simexec.c` probably won't work
+but it wouldn't be of much use anyway.

simexec/simexec.c

@@ -1,7 +1,10 @@
 #include <stdio.h> /* fprintf(3), NULL */
-#include <sysexits.h> /* EX_USAGE */
 #include <unistd.h> /* execv(3), */
 
+#if !defined EX_USAGE
+#	include <sysexits.h> /* EX_USAGE */
+#endif
+
 static char *program_name = "simexec";
 
 int main(int argc, char *argv[]){