disable colorization on !tty devices, add option to force colorization

tools/osmpbf-outline.cpp

@@ -4,6 +4,9 @@
 // file io lib
 #include <stdio.h>
 
+// getopt is used to check for the --color-flag
+#include <getopt.h>
+
 // zlib compression is used inside the pbf blobs
 #include <zlib.h>
 
@@ -13,6 +16,9 @@
 // this is the header to pbf format
 #include <osmpbf/osmpbf.h>
 
+// should the output use color?
+bool usecolor = false;
+
 // buffer for reading a compressed blob from file
 char buffer[OSMPBF::max_uncompressed_blob_size];
 
@@ -33,9 +39,15 @@ OSMPBF::PrimitiveBlock primblock;
 
 // prints a formatted message to stdout, optionally color coded
 void msg(const char* format, int color, va_list args) {
+    if(usecolor) {
         fprintf(stdout, "\x1b[0;%dm", color);
+    }
     vfprintf(stdout, format, args);
+    if(usecolor) {
         fprintf(stdout, "\x1b[0m\n");
+    } else {
+        fprintf(stdout, "\n");
+    }
 }
 
 // prints a formatted message to stderr, color coded to red
@@ -73,12 +85,34 @@ void debug(const char* format, ...) {
 
 // application main method
 int main(int argc, char *argv[]) {
+    // check if the output is a tty so we can use colors
+    usecolor = isatty(1);
+
+    static struct option long_options[] = {
+        {"color",                no_argument, 0, 'c'},
+    };
+
+    while (1) {
+        int c = getopt_long(argc, argv, "c", long_options, 0);
+
+        if (c == -1)
+            break;
+
+        switch (c) {
+            case 'c':
+                usecolor = true;
+                break;
+            default:
+                exit(1);
+        }
+    }
+
     // check for proper command line args
-    if(argc != 2)
+    if(optind != argc-1)
-        err("usage: %s file.osm.pbf", argv[0]);
+        err("usage: %s [--color] file.osm.pbf", argv[0]);
 
     // open specified file
-    FILE *fp = fopen(argv[1], "r");
+    FILE *fp = fopen(argv[optind], "r");
 
     // read while the file has not reached its end
     while(!feof(fp)) {