diff --git a/sim/GetLineNum.do b/sim/GetLineNum.do
new file mode 100644
index 00000000..4d38d912
--- /dev/null
+++ b/sim/GetLineNum.do
@@ -0,0 +1,18 @@
+# Alec Vercruysse
+# 2023-04-12
+# Note that the target string is regex, and needs to be double-escaped.
+# e.g. to match a (, you need \\(.
+proc GetLineNum {fname target} {
+    set f [open $fname]
+    set linectr 1
+    while {[gets $f line] != -1} {
+         if {[regexp $target $line]} {
+             close $f
+             return $linectr
+         }
+         incr linectr
+     }
+    close $f
+    return -code error \
+         "target string not found"
+}