From 58bf971d69ade1876af52e28002e84de6b372fca Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Denilson=20Figueiredo=20de=20S=C3=A1?=
 <denilsonsa@gmail.com>
Date: Fri, 26 Jun 2015 08:13:29 -0300
Subject: [PATCH] Returning non-zero status in case of error in parameters

Knowing when something happened correctly and when an error occurred is important when using zopflipng in other scripts.

In special, if the help message is printed without passing `-h` or `--help`, it happened because of wrong or missing parameters, and should return a non-zero status. However, passing `-h` or `--help` will return 0.
---
 src/zopflipng/zopflipng_bin.cc | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/zopflipng/zopflipng_bin.cc b/src/zopflipng/zopflipng_bin.cc
index 9d0798a6..f03573fc 100644
--- a/src/zopflipng/zopflipng_bin.cc
+++ b/src/zopflipng/zopflipng_bin.cc
@@ -136,7 +136,7 @@ void PrintResultSize(const char* label, size_t oldsize, size_t newsize) {
 int main(int argc, char *argv[]) {
   if (argc < 2) {
     ShowHelp();
-    return 0;
+    return 1;
   }
 
   ZopfliPNGOptions png_options;
@@ -171,7 +171,7 @@ int main(int argc, char *argv[]) {
           return 0;
         } else {
           printf("Unknown flag: %c\n", c);
-          return 0;
+          return 1;
         }
       }
     } else if (arg[0] == '-' && arg.size() > 1 && arg[1] == '-') {
@@ -227,7 +227,7 @@ int main(int argc, char *argv[]) {
         if (!correct) {
           printf("Error: keepchunks format must be like for example:\n"
                  " --keepchunks=gAMA,cHRM,sRGB,iCCP\n");
-          return 0;
+          return 1;
         }
       } else if (name == "--prefix") {
         use_prefix = true;
@@ -237,7 +237,7 @@ int main(int argc, char *argv[]) {
         return 0;
       } else {
         printf("Unknown flag: %s\n", name.c_str());
-        return 0;
+        return 1;
       }
     } else {
       files.push_back(argv[i]);
@@ -253,7 +253,7 @@ int main(int argc, char *argv[]) {
     } else {
       printf("Please provide one input and output filename\n\n");
       ShowHelp();
-      return 0;
+      return 1;
     }
   }