2 files changed, 197 insertions, 3 deletions

diff --git a/doc/info/librarian.texinfo b/doc/info/librarian.texinfo
index 7d3b416..cc26211 100644
--- a/doc/info/librarian.texinfo
+++ b/doc/info/librarian.texinfo
@@ -148,7 +148,9 @@ Upper cased arguments are interpreted as
 @code{VARIABLE} options, other arguments are
 interpreted as @code{LIBRARY} options, and
 should be, but are not required to be, lower
-cased.
+cased. Additionally, @code{VARIABLE} may only
+consist of letters, digits, @code{_} (underscore),
+@code{-} (hyphen).
 
 If @code{VARIABLE} is omitted, the process will
 exit with the value @code{0} if all listed libraries,
diff --git a/src/librarian.c b/src/librarian.c
index 7d3b4d4..8179f76 100644
--- a/src/librarian.c
+++ b/src/librarian.c
@@ -21,10 +21,202 @@
  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  * DEALINGS IN THE SOFTWARE.
  */
+#include <stdio.h>
+#include <ctype.h>
+#include <string.h>
+#include <stdlib.h>
+#include <assert.h>
 
+#define  t(...)  do { if (__VA_ARGS__) goto fail; } while (0)
 
-int main(void)
+
+/**
+ * The name of the process.
+ */
+static const char *argv0;
+
+
+/**
+ * A library and version range.
+ */
+struct library {
+	/**
+	 * The name of the library.
+	 */
+	const char *name;
+
+  	/**
+	 * The lowest acceptable version.
+	 * `NULL` if unbounded.
+	 */
+	const char *lower;
+
+  	/**
+	 * The highest acceptable version.
+	 * `NULL` if unbounded.
+	 */
+	const char *upper;
+
+  	/**
+	 * Is the version stored in
+	 * `lower` acceptable.
+	 */
+	int lower_closed;
+
+  	/**
+	 * Is the version stored in
+	 * `ypper` acceptable.
+	 */
+	int upper_closed;
+};
+
+
+
+/**
+ * Determine whether a string is the
+ * name of a non-reserved variable.
+ * 
+ * @param   s  The string.
+ * @return     1: The string is a varible name.
+ *             0: The string is a library.
+ */
+static int is_variable(const char *s)
 {
-  return 0;
+	for (; *s; s++) {
+		if      (isupper(*s))       ;
+		else if (isdigit(*s))       ;
+		else if (strchr("_-", *s))  ;
+		else
+			return 0;
+	}
+	return 1;
+}
+
+
+/**
+ * Parse a library–library-version range
+ * argument.
+ * 
+ * @param   s    The string.
+ * @param   lib  Output parameter for the library spec:s.
+ * @return       0: Successful.
+ *               1: Syntax error.
+ */
+static int parse_library(char *s, struct library *lib)
+{
+#define CLEANUP  \
+	free(libraries)
+
+	char *p;
+	char c;
+
+	memset(lib, 0, sizeof(*lib));
+
+	if (strchr(s, '/') || strchr("<>=", *s))
+		return 1;
+
+	lib->name = s;
+	p = strpbrk(s, "<>=");
+	if (p == NULL)
+		return 0;
+	c = *p, *p++ = '\0';
+
+	switch (c) {
+	case '=':
+		lib->lower_closed = lib->upper_closed = 1;
+		lib->lower = lib->upper = p;
+		break;
+	case '>':
+		p += lib->lower_closed = (*p == '=');
+		lib->lower = p;
+		s = strchr(p, '<');
+		if (s == NULL)
+			break;
+		*s++ = '\0';
+		if (!*(p = s))
+			return 0;
+		/* fall through */
+	case '<':
+		p += lib->upper_closed = (*p == '=');
+		lib->upper = p;
+		break;
+	default:
+		assert(0);
+		abort();
+		break;
+	}
+
+	return (strpbrk(p, "<>=") || !*p);
+}
+
+
+/**
+ * @return  0: Program was successful.
+ *          1: An error occurred.
+ *          2: A library was not found.
+ *          3: Usage error.
+ */
+int main(int argc, char *argv[])
+{
+	int dashed = 0, f_deps = 0, f_locate = 0, f_oldest = 0;
+	char *arg;
+	char **args = argv;
+	char **args_last = argv;
+	char **variables = argv;
+	char **variables_last = argv;
+	struct library *libraries = NULL;
+	struct library *libraries_last;
+
+	/* Parse arguments. */
+	argv0 = argv ? (argc--, *argv++) : "pp";
+	while (argc) {
+		if (!dashed && !strcmp(*argv, "--")) {
+			dashed = 1;
+			argv++;
+			argc--;
+		} else if (!dashed && (**argv == '-')) {
+			arg = *argv++;
+			argc--;
+			if (!*arg)
+				goto usage;
+			for (arg++; *arg; arg++) {
+				if (*arg == 'd')
+					f_deps = 1;
+				else if (*arg == 'l')
+					f_locate = 1;
+				else if (*arg == 'o')
+					f_oldest = 1;
+				else
+					goto usage;
+			}
+		} else {
+			*args_last++ = *argv++;
+			argc--;
+		}
+	}
+
+	/* Parse VARIABLE and LIBRARY arguments. */
+	libraries = malloc((size_t)(args_last - args) * sizeof(*libraries));
+	libraries_last = libraries;
+	t (libraries == NULL);
+	for (; args != args_last; args++) {
+		if (is_variable(*args))
+			*variables_last = *args;
+		else if (parse_library(*args, libraries_last++))
+			goto usage;
+	}
+
+	CLEANUP;
+	return 0;
+
+fail:
+	perror(argv0);
+	CLEANUP;
+	return 1;
+
+usage:
+	fprintf(stderr, "%s: Invalid arguments, see `man 1 librarian'.\n", argv0);
+	CLEANUP;
+	return 3;
 }