Implement tail command to read file lines

src/userland/cli/tail.c

@@ -0,0 +1,68 @@
+// Copyright (c) 2026 janevers (https://github.com/janevers-sys)
+// This software is released under the GNU General Public License v3.0. See LICENSE file for details.
+// This header needs to maintain in any file it is present in, as per the GPL license terms.
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
+int main(int argc, char *argv[]) {
+    // print all lines
+    if (argc == 2) {
+        if(strcmp(argv[1], "--help")) {
+            printf("-This command reads from the back of the file\n");
+            printf("-Use: tail [-n] [-number of lines] [file]\n");
+            return 0;
+        }
+        FILE *fp = fopen(argv[1], "r");
+        if (fp == NULL) {
+            printf("File not found\n");
+            return 1;
+        }
+        char buf[1024];
+        while (fgets(buf, sizeof(buf), fp)) {
+            printf("%s", buf);
+        }
+        fclose(fp);
+        return 0;
+    }
+    // only print last lines 
+    if (argc == 4 && strcmp(argv[1], "-n") == 0) {
+        int lines = atoi(argv[2]);
+        if (lines <= 0) {
+            printf("Number of lines should be positive\n");
+            return 1;
+        }
+
+        FILE *fp = fopen(argv[3], "r");
+        if (fp == NULL) {
+            printf("File not found\n");
+            return 1;
+        }
+
+        // count total lines
+        int count = 0;
+        char buf[1024];
+        while (fgets(buf, sizeof(buf), fp)) {
+            count++;
+        }
+
+        // back to start of file
+        fseek(fp, 0, SEEK_SET);
+
+        // check if lines are the end lines
+        int skip = count - lines;
+        int i = 0;
+        while (fgets(buf, sizeof(buf), fp)) {
+            if (i >= skip) {
+                printf("%s", buf);
+            }
+            i++;
+        }
+
+        fclose(fp);
+        return 0;
+    }
+
+    printf("Wrong flag, --help for more info\n");
+    return 1;
+}