separate out libpsargs

libpsargs/libpsargs.h

@@ -0,0 +1,17 @@
+/* pscat(1) and pspipe(1) arguments are flanked by { '[', '\0' } and
+ * { ']', '\0' }. Nesting is allowed to facilitate nesting of pscat(1) and
+ * pspipe(1). This checks to make sure grouping symbols in args are balanced.
+ * args is the argv that was passed to main, incremented. l is the left
+ * grouping character (usually '[') and r is the right grouping character
+ * (usually ']').
+ * Returns 0 in the events of a syntax error or there being no arguments.
+ * Otherwise, returns the number of top-level right grouping arguments
+ * (i.e. the number of terms). */
+int check_arg(char **args, char l, char r);
+
+/* arg is the location of the argument with the left grouping symbol within
+ * argv, l is the left grouping character itself, r is the right grouping
+ * character itself.
+ * Returns the location of the argument with the corresponding left grouping
+ * symbol within argv. */
+char **corresponding_arg(char **arg, char l, char r);