taps: fix error messages

pkgs/taps/main.c

@@ -10,7 +10,7 @@
 #include <pwd.h>
 #include <fnmatch.h>
 #include <fcntl.h> /* open, O_NONBLOCK, &c */
-#include <stdio.h> /* perror */
+#include <error.h>
 #include <errno.h>
 #include <sys/ioctl.h>
 
@@ -31,8 +31,7 @@
 #define DO_OR_DIE(expr) DO_OR_DIE_X((expr) == 0)
 #define DO_OR_DIE_X(expr) \
     do if (!(expr)) { \
-        perror((#expr)); \
-        exit(EXIT_FAILURE); \
+        error(EXIT_FAILURE, errno, ("Failed assertion: " #expr)); \
     } while(false)
 
 struct allow_pattern {
@@ -214,6 +213,7 @@ int main(int argc, char **argv) {
 
     char **rest = argv + 1;
 
+    DO_OR_DIE_X(argc > 1);
     if (strcmp(rest[0], "serve") == 0) {
         cmdServe = true;
         ++rest;
@@ -221,21 +221,26 @@ int main(int argc, char **argv) {
         cmdGet = true;
         ++rest;
     } else {
-        exit(EXIT_FAILURE);
+        error(EINVAL, EINVAL, "no subcommand \"%s\"", rest[0]);
     }
 
     const char *patternsRaw = secure_getenv("TAPS_ALLOW");
     struct allow_patterns patterns = { 0 };
-    if (cmdServe && patternsRaw != NULL) { patterns = parsePatterns(patternsRaw); }
+    if (cmdServe && patternsRaw != NULL) {
+        patterns = parsePatterns(patternsRaw);
         DO_OR_DIE_X(patterns.patterns != NULL);
+    }
 
     const char *servePath = secure_getenv("TAPS_SOCK");
 
-    if (cmdServe && patterns.patterns != NULL) {
+    if (cmdServe) {
+        error(patterns.patterns == NULL, EINVAL, "TAPS_ALLOW");
         acceptRequests(servePath, &patterns);
     } else if (cmdGet) {
+        error(ENOSYS, ENOSYS, "get");
     } else {
-        exit(EXIT_FAILURE); }
+        error(EINVAL, EINVAL, "subcommand args");
+    }
 
     return 0;
 }

shell.nix

@@ -6,5 +6,8 @@ mkShell.override { stdenv = stdenvNoCC; } {
     virtiofsd
     crosvm # virtio-gpu
     npins
+  ] ++ [
+    man-pages
+    linux-manual
   ];
 }