If the compatibility flags ki or eg are set, the 'write' command

will not use function parsing and evaluation, but simply plot
the listed vectors. vec1 vs vec2 is also not supported.
This option is useful if node names vs+ or /mynode are used and
have to be written into a raw file, as may be used by KiCad or EAGLE.

src/frontend/postcoms.c

@@ -23,6 +23,7 @@ Author: 1985 Wayne A. Christopher, U. C. Berkeley CAD Group
 #include "parser/complete.h" /* va: throwaway */
 #include "plotting/plotting.h"
 
+#include "ngspice/compatmode.h"
 
 static void killplot(struct plot *pl);
 static void DelPlotWindows(struct plot *pl);
@@ -433,7 +434,7 @@ com_write(wordlist *wl)
     struct pnode *pn;
     struct dvec *d, *vecs = NULL, *lv = NULL, *end, *vv;
     static wordlist all = { "all", NULL, NULL };
-    struct pnode *names;
+    struct pnode *names = NULL;
     bool ascii = AsciiRawFile;
     bool scalefound, appendwrite;
     struct plot *tpl, newplot;
@@ -455,25 +456,43 @@ com_write(wordlist *wl)
     }
     appendwrite = cp_getvar("appendwrite", CP_BOOL, NULL, 0);
 
-    if (wl)
-        names = ft_getpnames(wl, TRUE);
-    else
-        names = ft_getpnames(&all, TRUE);
+    /* If use with EAGLE or KiCad compatibility, we do not expand equations, serve v vs vs etc.
+       We offer plain writing of the vectors. This enables node names containing +, -, / etc. */
+    if (!newcompat.eg && !newcompat.ki) {
+        if (wl)
+            names = ft_getpnames(wl, TRUE);
+        else
+            names = ft_getpnames(&all, TRUE);
 
-    if (names == NULL) {
-        return;
-    }
+        if (names == NULL) {
+            return;
+        }
 
-    for (pn = names; pn; pn = pn->pn_next) {
-        d = ft_evaluate(pn);
-        if (!d)
-            goto done;
-        if (vecs)
-            lv->v_link2 = d;
-        else
-            vecs = d;
-        for (lv = d; lv->v_link2; lv = lv->v_link2)
-            ;
+        for (pn = names; pn; pn = pn->pn_next) {
+            d = ft_evaluate(pn);
+            if (!d)
+                goto done;
+            if (vecs)
+                lv->v_link2 = d;
+            else
+                vecs = d;
+            for (lv = d; lv->v_link2; lv = lv->v_link2)
+                ;
+        }
+    }
+    else {
+        wordlist* wli;
+        for (wli = wl; wli; wli = wli->wl_next) {
+            d = vec_get(wli->wl_word);
+            if (!d)
+                goto done;
+            if (vecs)
+                lv->v_link2 = d;
+            else
+                vecs = d;
+            for (lv = d; lv->v_link2; lv = lv->v_link2)
+                ;
+        }
     }
 
     /* Now we have to write them out plot by plot. */