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README.md

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+# AAE-CNAS-Labs
+
+Repository with tasks for Computer Networks and Systems laboratory classes
+
+## Topic 1 – Little warmup
+I'm sure you are all proficient C/C++ programmers, but - just in case you had a long break and forgot some things - lets do a little warmup.
+
+Write your own version of Unix "cp" (copy) command.
+
+As a bare minimum - please write a program that:
+ - accepts source and destination filenames as its arguments (you DO remember how to use argc and argv ?)
+ - makes a copy of indicated file
+  - returns 0 on success, any non-zero value on error
+  - uses ONLY POSIX I/O functions (open, close, read, write - consult appropriate manuals)
+
+NOTICE: Do not assume, that you can read entire file into memory. Please read manuals carefully - pay attention to each function's return value!
+
+I'm sure this task will prove to be to easy to some of you - in this case you can extend your program - for example you can add features to allow:
+ - copy source_file dest_dir  (copy source file to the indicated directory, keeping its name)
+ - copy file1 file2 file3 dest_dir (copy files file1...file3 into destination directory)
+ - ... ?
+
+As a solution - provide your source code here.

Topic-1/main.c

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+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
+enum ERROR{NO_ARGUMENTS, WRONG_ARGUMENT};
+
+int print_error_message(enum ERROR error_type) {
+    if (error_type == NO_ARGUMENTS) {
+        fprintf(stderr,"cp: missing file operand\n"); // TODO: Maybe replace "cp" with argv[0]?
+        fprintf(stderr,"Try cp --help for more information.\n");
+        return 0;
+    } else if (error_type == WRONG_ARGUMENT) {
+        fprintf(stderr, "cp: unrecognized option\n");
+        fprintf(stderr,"Try cp --help for more information.\n");
+    }
+    return 0;
+}
+
+int print_help() {
+    printf("HELP\n");
+    return 0;
+}
+
+int cp(char *argv[]){
+    printf("%s\n", argv[0]);
+    open();
+    return 0;
+}
+
+int main(int argc, char *argv[]) {
+    if (argc == 1) {
+        print_error_message(NO_ARGUMENTS);
+        return 1;
+    }
+    if (argc == 2) {
+        if (strcmp(argv[1], "--help") == 0) {
+            print_help();
+            return 0;
+        } else {
+            print_error_message(WRONG_ARGUMENT);
+            return 2;
+        }
+    }
+    if (argc == 3) {
+        cp(argv);
+    }
+    return 0;
+}