1 files changed, 152 insertions, 0 deletions
diff --git a/src/commands/cat.c b/src/commands/cat.c
new file mode 100644
index 0000000..e2c471b
--- /dev/null
+++ b/src/commands/cat.c
@@ -0,0 +1,152 @@
+#include "../command.h"
+
+#include <ctype.h>
+#include <string.h>
+
+struct Flags {
+    bool number_lines;
+    bool number_non_empty;
+    bool change_non_print;
+    bool change_tabs;
+    bool end_lines_dollar;
+};
+
+static bool printable(char c) {
+    switch (c) {
+        case '\n': return true;
+        case '\r': return true;
+        case '\b': return true;
+        case '\t': return true;
+        default: return isprint(c);
+    }
+}
+
+static void help() {
+    printf("Usage: cat [-nbvteA] [FILE]...\n\n");
+    printf("Print FILEs to stdout\n\n");
+	printf("-n	Number output lines\n");
+	printf("-b	Number nonempty lines\n");
+	printf("-v	Show nonprinting characters as ^x or M-x\n");
+	printf("-t	...and tabs as ^I\n");
+	printf("-e	...and end lines with $\n");
+	printf("-A	Same as -vte\n");
+    exit(EXIT_SUCCESS);
+}
+
+static void cat_file(FILE* file, struct Flags flags) {
+    char c;
+    size_t read;
+    
+    size_t line = 1;
+    bool empty = true;
+    bool newline = true;
+    
+    while ((read = fread(&c, 1, 1, file)) != 0) {
+        if (c == '\n') {
+            if (empty && flags.number_lines) {
+                printf("\t%ld ", line);
+            }
+            if (flags.end_lines_dollar) {
+                printf("$");
+            }
+            line++;
+            newline = true;
+            empty = true;
+            goto print;
+        } else {
+            empty = false;
+        }
+
+        if (!newline) {
+            goto print;
+        }
+
+        if (!empty && (flags.number_non_empty || flags.number_lines)) {
+            printf("\t%ld ", line);
+            newline = false;
+        }
+    print:
+        if (!flags.change_non_print || printable(c)) {
+            if (flags.change_tabs && c == '\t') {
+                fwrite("^I", 1, 2, stdout);
+            } else {
+                fwrite(&c, 1, 1, stdout);
+            }
+        } else {
+            c |= '@';
+            fwrite(&c, 1, 1, stdout);
+        }
+    }
+}
+
+COMMAND(cat) {
+
+    struct Flags flags;
+    flags.number_lines = false;
+    flags.number_non_empty = false;
+    flags.change_non_print = false;
+    flags.change_tabs = false;
+    flags.end_lines_dollar = false;
+
+    for (int i = 0; i < argc; i++) {
+        if (!prefix("-", argv[i])) {
+            continue;
+        }
+
+        if (streql("--help", argv[i])) {
+            help();
+        }
+
+        size_t len = strlen(argv[i] + 1);
+        for (size_t j = 0; j < len; j++) {
+            char c = argv[i][j + 1];
+            switch (c) {
+                case 'n':
+                    flags.number_lines = true;
+                    break;
+                case 'b':
+                    flags.number_non_empty = true;
+                    break;
+                case 'v':
+                    flags.change_non_print = true;
+                    break;
+                case 't':
+                    flags.change_non_print = true;
+                    flags.change_tabs = true;
+                    break;
+                case 'e':
+                    flags.change_non_print = true;
+                    flags.end_lines_dollar = true;
+                    break;
+                case 'A':
+                    flags.change_non_print = true;
+                    flags.change_tabs = true;
+                    flags.end_lines_dollar = true;
+                    break;
+                default:
+                    error("error: unkown flag -%c", c);
+            }
+        } 
+    }
+
+    bool files = false;
+    for (int i = 0; i < argc; i++) {
+        if (streql("-", argv[i])) {
+            files = true;
+            cat_file(stdin, flags);
+        } else if (prefix("-", argv[i])) {
+            continue;
+        } else {
+            files = true;
+            FILE* in = get_file(argv[i], "r");
+            cat_file(in, flags);
+            fclose(in);
+        }
+    }
+
+    if (!files) {
+        cat_file(stdin, flags);
+    }
+    
+    return EXIT_SUCCESS;
+}