Add more user program

Author: scopeInfinity

src/usr/local/src/cat.c

@@ -1,4 +1,4 @@
-// list directory
+// print content of file
 #include <stdio.h>
 #include <string.h>
 

src/usr/local/src/more.c

@@ -0,0 +1,56 @@
+// buffered print content of file
+#include <stdio.h>
+#include <string.h>
+
+// assumption
+#define SCREEN_WIDTH  0x50
+#define SCREEN_HEIGHT 0x19
+
+void process(char filename[]) {
+    FILE *handler = fopen(filename, "r");
+    if(handler==NULL) {
+        printf("failed to open '%s' file.\n", filename);
+        return;
+    }
+    char buffer[SCREEN_WIDTH+1];
+    int count_before_buffer = SCREEN_HEIGHT-2;
+    while(1) {
+        if (!fgets(buffer, sizeof(buffer), handler)) {
+            int err = ferror(handler);
+            if(err) {
+                printf("Error: failed to read next chunk, code %d\n", err);
+                exit(err);
+            }
+            break;
+        }
+        puts(buffer);
+        if(count_before_buffer>0) {
+            count_before_buffer--;
+        } else {
+            // buffer
+            char c = getch();
+            if(c=='q' || c=='Q') {
+                exit(0);
+            }
+            // continue
+        }
+    }
+    fclose(handler);
+}
+
+int print_usage() {
+    printf("Usage: more <filename>\n");
+    printf(" > buffer will start when output takes over the whole screen\n");
+    printf(" > press 'q' to exit\n");
+    printf(" > press any other key to scroll down\n");
+    return 0;
+}
+
+int main(int argc, char *argv[]) {
+    if (argc != 2) {
+        return print_usage();
+    }
+    char *filename = argv[1];
+    process(filename);
+    return 0;
+}