README and fd: start a note to tell what I'm doing here ...

Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>

README.md

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+# tmp.c
+
+Hacking around with C/C++ basics to get myself comfortable and up to speed.
+To a large extent, making myself attempt to do small projects in C/C++ as a default.
+
+## Links
+
+- [GNU C Library manual](https://www.gnu.org/software/libc/manual/html_node/index.html)
+- [21 Century C++ by Bjarne Stroustrup](https://cacm.acm.org/blogcacm/21st-century-c/) ([joplin copy](joplin://x-callback-url/openNote?id=8bea21d4cd134ceeaeeaff01f33427cd))
+

fd.cpp

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+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+int main() {
+    // Open a file for reading and writing
+    int fd = open("example.txt", O_RDWR | O_CREAT, S_IRUSR | S_IWUSR);
+    // int fd = 2; // jam in STDERR_FILENO ...
+    if (fd == -1) {
+        perror("Error opening file");
+        return EXIT_FAILURE;
+    }
+
+    // Write to the file
+    const char *text = "Hello, file descriptors!";
+    ssize_t bytes_written = write(fd, text, strlen(text));
+    if (bytes_written == -1) {
+        perror("Error writing to file");
+        close(fd);
+        return EXIT_FAILURE;
+    }
+
+    // Move the file offset to the beginning
+    if (lseek(fd, 0, SEEK_SET) == -1) {
+        perror("Error seeking in file");
+        close(fd);
+        return EXIT_FAILURE;
+    }
+
+    // Read from the file
+    char buffer[256];
+    ssize_t bytes_read = read(fd, buffer, sizeof(buffer) - 1);
+    if (bytes_read == -1) {
+        perror("Error reading from file");
+        close(fd);
+        return EXIT_FAILURE;
+    }
+
+    // Null-terminate the buffer and print the content
+    buffer[bytes_read] = '\0';
+    printf("File content: %s\n", buffer);
+
+    // Close the file
+    if (close(fd) == -1) {
+        perror("Error closing file");
+        return EXIT_FAILURE;
+    }
+
+    return EXIT_SUCCESS;
+}