help text, args, and custom gradient

colcat.c

@@ -10,11 +10,29 @@
 int rainbow_len = 90;   // how many characters long is one full rainbow (360deg)
 int col_change = -1;         // how many degrees between colours in the rainbow
 int col_dist = -1;           // how many characters per colour in output
-int frequency = -1;          // how many degrees to rotate start point on new line
+int frequency = -1;          // how many degrees to rotate start_hue point on new line
 
 struct colour* colours; // the rainbow 
 int num_colours;        // the length of the rainbow
 
+// start_hue and end_hue hue values
+int start_hue = -1;
+int end_hue = -1;
+
+char help_text[] = "\nUsage: colcat [args] [--] [FILES] \n"
+                     "\n"
+                     "Concatenate files (or standard input) and print on the standard\n"
+                     "output, with a rainbow colour. The colour range and repeat\n"
+                     "distance can be specified.\n\n"
+                     "Args:\n\n"
+                     "      -h           Print help text and exit\n"
+                     "      -w <int>     Width, in chars, of the rainbow sequence\n"
+                     "      -r <int>     The amount the hue is rotated on new lines\n"
+                     "      -s <int>     The hue to start the rainbow at\n"
+                     "      -e <int>     The hue to end the rainbow at\n"
+                     "\n";
+
+
 /* Print the nth colour of the <rainbow_len> chars long rainbow */
 void print_next_colour(int current) {
     if (current % col_dist == 0) {
@@ -23,8 +41,8 @@ void print_next_colour(int current) {
     }
 }
 
-/* Checks if a car is a possible ANSI escape code ending */
-bool end_ansi_code(char c) {
+/* Checks if a car is a possible ANSI escape code end_hueing */
+bool end_hue_ansi_code(char c) {
     char codes[] = "HfABCDsuJKmhlP";
     for (int i = 0; i < strlen(codes); i++) {
         if (c == codes[i]) {
@@ -38,16 +56,16 @@ bool end_ansi_code(char c) {
 int display(FILE *file) {
     char c = fgetc(file);
 
-    int start = 0;
+    int start_hue = 0;
     int counter = 0;
     bool in_escape = false;
     while (c != EOF) {
         if (c == '\n') {
-            counter = (start += frequency);
+            counter = (start_hue += frequency);
         }
         if (c == '\033') {
             in_escape = true;
-        } else if (end_ansi_code(c) && in_escape) {
+        } else if (end_hue_ansi_code(c) && in_escape) {
             in_escape = false;
             putc(c, stdout);
             c = fgetc(file);
@@ -85,26 +103,40 @@ int open_and_cat(char *file_name) {
  * rainbow out again
  */
 int generate_rainbow() {
-    if (rainbow_len < 360) {
+
+    if (start_hue == -1) {
+        start_hue = 0;
+    }
+    if (end_hue == -1) {
+        end_hue = 360;
+    }
+
+    if (end_hue < start_hue) {
+        exit(1);
+    }
+
+    int arclen = end_hue - start_hue;
+
+    if (rainbow_len < arclen) {
         num_colours = rainbow_len;
-        col_change = 360 / num_colours;
+        col_change = arclen / num_colours;
         if (col_change == 0) {
             col_change = 1;
         }
     } else {
-        num_colours = 360;
+        num_colours = arclen;
         col_change = 1;
     }
 
     col_dist = (rainbow_len) / (num_colours);
     colours = calloc(num_colours, sizeof(struct colour));
     struct colour c;
-    c.h = 0;
+    c.h = start_hue;
     c.s = 1;
     c.v = 1;
     c.sp = CS_HSV;
     for (int i = 0; i < num_colours; i++) {
-        c.h = (int)(c.h + col_change) % 360;
+        c.h = (int)(c.h + col_change) % arclen;
         colours[i] = get_rgb(c);
     }
 
@@ -115,16 +147,26 @@ int generate_rainbow() {
 int main(int argc, char** argv) {
     int opt;
     int optcount = 0;
-    while ((opt = getopt(argc, argv, "h:v:")) != -1) {
+    while ((opt = getopt(argc, argv, "hw:r:s:e:")) != -1) {
         optcount++;
-        if (opt == 'h') {
+        if (opt == 'w') {
             optcount++;
             rainbow_len = atoi(optarg);
-        } else if (opt == 'v') {
+        } else if (opt == 'r') {
             optcount++;
             frequency = atoi(optarg);
+        } else if (opt == 's') {
+            optcount++;
+            start_hue = atoi(optarg);
+        } else if (opt == 'e') {
+            optcount++;
+            end_hue = atoi(optarg);
+        } else if (opt == 'h') {
+            printf("%s", help_text);
+            exit(0);
         } else {
-            printf("Usage: colcat -h [rainbow length] -v [vertical frequency]");
+            printf("%s", help_text);
+            exit(1);
         }
     }
 

readme.md

@@ -1,8 +1,8 @@
-# colcat
+# colcat (lolcat)
 
 Another lolcat clone, in 2020. 
 
-![image showing square of repeating 'a's in rainbow colour](demo.png)
+![image showing help text in rainbow colour](demo.png)
 
 This is probably the least feature-complete version of lolcat, (the `cat` clone
 that makes the output rainbow), but I wrote it anyway and probably won't do any
@@ -13,7 +13,20 @@ It seems to mostly be compatible with other ANSI codes now.
 
 Options:
 
-    colcat -h [rainbow width] -v [how much the hue is rotated each line]
+    Usage: colcat [args] [--] [FILES]
+
+    Concatenate files (or standard input) and print on the standard
+    output, with a rainbow colour. The colour range and repeat
+    distance can be specified.
+
+    Args:
+
+          -h           Print help text and exit
+          -w <int>     Width, in chars, of the rainbow sequence
+          -r <int>     The amount the hue is rotated on new lines
+          -s <int>     The hue to start the rainbow at
+          -e <int>     The hue to end the rainbow at
+
 
 It is the norm for these programs to fuzz the rainbow a bit, and provide more 
 options for the frequency and animation options. Mine doesn't have animation, 
@@ -38,7 +51,7 @@ Installs `colcat` to `/usr/local/bin/`
 
 ## Similar Programs
 
+- [busyloop/lolcat](https://github.com/busyloop/lolcat/) (Ruby) - the original
 - [jaseg/lolcat](https://github.com/jaseg/lolcat) ( C )
-- [busyloop/lolcat](https://github.com/busyloop/lolcat/) (Ruby)
 - [tehmaze/lolcat](https://github.com/tehmaze/lolcat/) (Python)
 - [gkbrk](https://gist.github.com/gkbrk/34ed7df44ba1400f31eb73a3f238faa7) (x64 Assembly)