nm: add page (osx and linux)

pages/linux/nm.md

@@ -0,0 +1,19 @@
+# nm
+
+> List symbol names in object files
+
+- List global (extern) functions in a file (prefixed with T)
+
+`nm -g {{file.o}}`
+
+- Demangle C++ symbols (make them readable)
+
+`nm --demangle {{file.o}}`
+
+- List only undefined symbols in a file
+
+`nm -u {{file.o}}`
+
+- List all symbols, even debugging symbols
+
+`nm -a {{file.o}}`