fileio.c

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/*
 * Copyright 2023 Morse Micro
 *
 * SPDX-License-Identifier: Apache-2.0
 */
 
#include <stdio.h>
#include <sys/unistd.h>
#include <sys/fcntl.h>
#include <sys/errno.h>
 
void app_init(void)
{
    printf("\n\nFile I/O Example (Built " __DATE__ " " __TIME__ ")\n\n");
 
    /* Open a file for reading - calling open() the first time automatically initializes
     * The file I/O subsystem and links in the required modules. */
    int fd = open("test.txt", O_RDONLY);
    if (fd < 0)
    {
        /* We got an error, check for @c EINVAL which signifies File I/O is not supported */
        if (errno == ENOENT)
        {
            /* We got a file not found error, so simply create the file */
            printf("File test.txt not found, creating...");
            fd = open("test.txt", O_RDWR | O_CREAT, 0644);
            if (fd >= 0)
            {
                char message[] = "G'day World!\n";
                int count = write(fd, message, sizeof(message));
                close(fd);
                if (count >= 0)
                {
                    printf("%d bytes written!\n"
                           "Run application again to see what was written.\n",
                           count);
                }
                else
                {
                    printf("Error %d!\n Failed to write to file!\n", errno);
                }
            }
            else
            {
                printf("Failed!\n");
            }
        }
        else
        {
            printf("File I/O is currently not supported on this platform!\n");
        }
    }
    else
    {
        /* File successfully opened, read contents */
        char buffer[64];
        int count = read(fd, buffer, sizeof(buffer) - 1);
        close(fd);
        if (count >= 0)
        {
            /* Ensure buffer is null terminated */
            buffer[count] = 0;
            printf("%d bytes read!\nContents: %s\n", count, buffer);
        }
        else
        {
            printf("Error %d!\nFailed to read from file!\n", errno);
        }
    }
}