diff --git a/src/bstr.c b/src/bstr.c
new file mode 100644
index 0000000..30a70eb
--- /dev/null
+++ b/src/bstr.c
@@ -0,0 +1,37 @@
+#include <stdarg.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
+#include "bstr.h"
+
+char *
+bstr_print(char *base, const char *fmt, ...)
+{
+    char *new_buf;
+    size_t new_len;
+    va_list ap;
+
+    va_start(ap, fmt);
+    new_len = vsnprintf(NULL, 0, fmt, ap);
+    va_end(ap);
+
+    new_buf = calloc(1, new_len + 1);
+
+    va_start(ap, fmt);
+    vsprintf(new_buf, fmt, ap);
+    va_end(ap);
+
+    if (!base) {
+        return new_buf;
+    } else {
+        size_t baselen = strlen(base);
+
+        base = realloc(base, baselen + new_len + 1);
+        memcpy(&base[baselen], new_buf, new_len);
+        base[baselen + new_len] = '\0';
+
+        free(new_buf);
+        return base;
+    }
+}
diff --git a/src/bstr.h b/src/bstr.h
new file mode 100644
index 0000000..c442da3
--- /dev/null
+++ b/src/bstr.h
@@ -0,0 +1,12 @@
+#ifndef _BSTR_H_
+#define _BSTR_H_
+
+#include <stdarg.h>
+#include <stdio.h>
+
+/* printf onto the end of base, reallocating and returning that buffer
+ * can provide NULL for no base */
+__attribute__((format(printf, 2, 3)))
+char *bstr_print(char *base, const char *fmt, ...);
+
+#endif /* _BSTR_H_ */
diff --git a/src/paths.c b/src/paths.c
new file mode 100644
index 0000000..7c4de57
--- /dev/null
+++ b/src/paths.c
@@ -0,0 +1,99 @@
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <inttypes.h>
+
+#include "bstr.h"
+#include "paths.h"
+
+#if __MINGW32__
+#  define BSTR_LLD "%I64d"
+#else
+#  define BSTR_LLD "%lld"
+#endif
+
+char *
+paths_append(char *base, const char *suffix)
+{
+    size_t baselen;
+    const char *sep = "";
+
+    if (!base)
+        return strdup(suffix);
+
+    baselen = strlen(base);
+
+    if (
+        (baselen == 0) ||
+        ((base[baselen-1] != '/') && (base[baselen-1] == '\\'))
+    ) {
+        /* no separator at end of path */
+#if __MINGW32__
+        sep = "\\";
+#else
+        sep = "/";
+#endif
+    }
+
+    return bstr_print(base, "%s%s", sep, suffix);
+}
+
+char *
+paths_bnconf_dir()
+{
+#ifdef __MINGW32__
+    char *home = getenv("HOMEPATH");
+#else
+    char *home = getenv("HOME");
+#endif
+    char *ret = NULL;
+
+    if (!home)
+        return NULL;
+
+#ifdef __MINGW32__
+    ret = strdup("C:\\");
+#endif
+    ret = paths_append(ret, home);
+    ret = paths_append(ret, ".config/bytenuts");
+
+    /* TODO free environment variable on Windows? */
+    return ret;
+}
+
+char *
+paths_bnconf_default()
+{
+    char *ret = paths_bnconf_dir();
+
+    if (!ret)
+        return NULL;
+
+    return paths_append(ret, "config");
+}
+
+char *
+paths_command_file(int idx)
+{
+    char *ret = paths_bnconf_dir();
+
+    if (!ret)
+        return NULL;
+
+    return bstr_print(ret, "/commands%d", idx);
+}
+
+char *
+paths_logfile(const char *prefix, long long pid)
+{
+    char *ret = paths_bnconf_dir();
+
+    if (!ret)
+        return NULL;
+
+    if (pid > 0) {
+        return bstr_print(ret, "/%s." BSTR_LLD ".log", prefix, pid);
+    } else {
+        return bstr_print(ret, "/%s.log", prefix);
+    }
+}
diff --git a/src/paths.h b/src/paths.h
new file mode 100644
index 0000000..179fafe
--- /dev/null
+++ b/src/paths.h
@@ -0,0 +1,20 @@
+#ifndef _PATHS_H_
+#define _PATHS_H_
+
+/* Realloc the base path and add the suffix to it, "/"s handled nicely */
+char *paths_append(char *base, const char *suffix);
+
+/* Get the ~/.config/bytenuts directory */
+char *paths_bnconf_dir();
+
+/* Get the default bytenuts config filepath */
+char *paths_bnconf_default();
+
+/* Generate the path to the command<idx> file */
+char *paths_command_file(int idx);
+
+/* Generate a logfile path of the form ~/.config/bytenuts/<prefix>[.<pid>].log
+ * PID only inserted if >0 */
+char *paths_logfile(const char *prefix, long long pid);
+
+#endif /* _PATHS_H_ */