From b360b823aca1907bbf5c1df63e4ffbdfe4779527 Mon Sep 17 00:00:00 2001
From: emma <emma@tebibyte.media>
Date: Thu, 10 Aug 2023 15:24:07 -0600
Subject: [PATCH] cat(1p): made simpler, added error handling

---
 src/cat.c | 60 +++++++++++++++++++++++++++++++++++++------------------
 1 file changed, 41 insertions(+), 19 deletions(-)

diff --git a/src/cat.c b/src/cat.c
index 250170d..455765f 100644
--- a/src/cat.c
+++ b/src/cat.c
@@ -30,18 +30,12 @@
 int main(int argc, char *argv[]) {
 	bool u = false;
 	int opt;
+	int i = 1;
 	FILE *file;
-	char *usage_text = "(-u) [file...]";
-	int buf_size = strlen(argv[0]) + strlen("Usage: ") + strlen(usage_text) + 3;
-	char *usage = calloc(buf_size, buf_size);
-
-	if ((
-		snprintf(usage, buf_size, "Usage: %s (-u) [file...]\n", argv[0])
-	) < 0 ) {}
 
 	extern int optind;
 	while ((opt = getopt(argc, argv, "u")) != -1) {
-		switch(opt) {
+		switch (opt) {
 			/*
 			 * From cat(1p):
 			 *
@@ -52,14 +46,15 @@ int main(int argc, char *argv[]) {
 				u = true;
 				break;
 			default:
-				break;
+				printf("Usage: %s (-u) file...\n", argv[0]);
+				return EX_USAGE;
 		}
 	}
-	argv += optind;
-	argc -= optind;
 
-	for (int i = 0; i < argc; i++) {
-		int byte = 0;
+	for (i = optind; i < argc; i++) {
+		int byte = 0; // variable for storing bytes as they are read
+		char buf[4096]; // buffer for buffered 
+		int p = 0; // index counter for bytes in buffered reading
 	  /*
 		 * From cat(1p):
 		 *
@@ -71,23 +66,50 @@ int main(int argc, char *argv[]) {
 		 *           but shall accept multiple occurrences of '-' as a file
 		 *           operand.
 		 */
-		if (argv[i] == "-" || argc == 0) {
+		if (argv[i] == "-" || argc == 1) {
 			file = stdin;
 		} else if ((file = fopen(argv[i], "r")) == NULL) {
-			// TODO: Add error handling
-			fputs(usage, stderr);
-			return EX_NOINPUT;
+			switch (errno) {
+				case EACCES:
+					printf("%s: %s: Permission denied.\n", argv[0], argv[i]);
+					return EX_NOINPUT;
+				case EISDIR:
+					printf("%s: %s: Is a directory.\n", argv[0], argv[i]);
+					return EX_NOINPUT;
+				case ELOOP:
+					printf("%s: %s: Is a symbolic link loop.\n", argv[0], argv[i]);
+					return EX_UNAVAILABLE;
+				case EMFILE:
+					printf("%s: Internal error.\n", argv[0]);
+					return EX_SOFTWARE;
+				case ENOENT: case ENOTDIR: case ENXIO:
+					printf("%s: %s: No such file or directory.\n", argv[0], argv[i]);
+					return EX_NOINPUT;
+				default:
+					printf("%s: Unknown error.\n", argv[0]);
+					return EX_UNAVAILABLE;
+			}
 		}
 
-		for (char *buf = calloc(4096, 1); byte != EOF; fputs(buf, stdout)) {
+		while (byte != EOF) {
 			byte = fgetc(file);
+
 			if (u) {
 				putchar(byte);
 			} else {
-				snprintf(buf, 4096, "%c", byte);
+				if (p > sizeof(buf)) {
+					fputs(buf, stdout);
+					p = 0;
+				}
+
+				buf[p] = byte;
+				p += 1;
 			}
 		}
 
+		fputs(buf, stdout);
+		fflush(stdout);
+
 		if (file != stdin) { fclose(file); }
 	}