From 340ca1a5bdf9a03819872f7370891b6bf5529441 Mon Sep 17 00:00:00 2001
From: Victor Mignot <victor@vmignot.fr>
Date: Wed, 4 Mar 2026 15:04:26 +0100
Subject: Add `cat` implementation

---
 src/cat.c | 74 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 74 insertions(+)
 create mode 100644 src/cat.c

(limited to 'src/cat.c')

diff --git a/src/cat.c b/src/cat.c
new file mode 100644
index 0000000..2370d29
--- /dev/null
+++ b/src/cat.c
@@ -0,0 +1,74 @@
+#include <errno.h>
+#include <fcntl.h>
+#include <getopt.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#define CAT_USAGE "Usage: cat [-u] [file...]\n"
+#define STDIN_ARG "-"
+#define BUFFER_SIZE 20480
+
+static void close_file(int fd) {
+	if (fd != STDIN_FILENO) {
+		close(fd);
+	}
+}
+
+static bool print_file_content(const char *path) {
+	char buffer[BUFFER_SIZE];
+	int input = -1;
+	ssize_t ret = -1;
+
+	if (strcmp(path, STDIN_ARG) == 0) {
+		input = STDIN_FILENO;
+	} else {
+		if ((input = open(path, O_RDONLY)) == -1) {
+			fprintf(stderr,"Can't open file '%s': %s\n", path, strerror(errno));
+			return false;
+		}
+	}
+
+	do {
+		ret = read(input, buffer, BUFFER_SIZE);
+		if (ret > 0) {
+			write(STDOUT_FILENO, buffer, ret);
+		}
+	} while (ret > 0);
+
+	if (ret == -1) {
+		fprintf(stderr, "Failed to read file '%s': %s\n", path, strerror(errno));
+	}
+
+	close_file(input);
+
+	return ret == 0;
+}
+
+int cat_main(int argc, char *argv[]) {
+	int opt = 0;
+	bool ret = false;
+
+	while ((opt = getopt(argc, argv, "u")) != -1) {
+		if (opt != 'u') {
+			perror(CAT_USAGE);
+			return EXIT_FAILURE;
+		}
+	}
+
+	for (int i = optind; i < argc; i++) {
+		ret = print_file_content(argv[i]);
+		if (!ret) {
+			break;
+		}
+	}
+
+	/* If no argument was provided, we use stdin by default */
+	if (argc - optind == 0) {
+		ret = print_file_content(STDIN_ARG);
+	}
+
+	return ret ? EXIT_SUCCESS : EXIT_FAILURE;
+}
-- 
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