/* append.c -- appends files to a file */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define BUFSIZE 1024
#define SLEN 81
void append(FILE *source, FILE *dest);

int main(void)
{
    FILE *fa, *fs;	// fa for append file, fs for source file
    int files = 0;  // number of files appended
    char file_app[SLEN];  // name of append file
    char file_src[SLEN];  // name of source file
    puts("Enter name of destination file:");
    gets(file_app);
    if ((fa = fopen(file_app, "a")) == NULL)
    {
        fprintf(stderr, "Can't open %s\n", file_app);
        exit(2); 
    }
    if (setvbuf(fa, NULL, _IOFBF, BUFSIZE) != 0)
    {
        fputs("Can't create output buffer\n", stderr);
        exit(3);
    }
    puts("Enter name of first source file (empty line to quit):");
    while (gets(file_src) && file_src[0] != '\0')
    {
        if (strcmp(file_src, file_app) == 0)
            fputs("Can't append file to itself\n",stderr);
        else if ((fs = fopen(file_src, "r")) == NULL)
            fprintf(stderr, "Can't open %s\n", file_src);
        else
        {
            if (setvbuf(fs, NULL, _IOFBF, BUFSIZE) != 0)
            {
                fputs("Can't create input buffer\n",stderr);
                continue;
            }
            append(fs, fa);
            if (ferror(fs) != 0)
                fprintf(stderr,"Error in reading file %s.\n",
                        file_src);
            if (ferror(fa) != 0)
                fprintf(stderr,"Error in writing file %s.\n",
                        file_app);
            fclose(fs);
            files++;
            printf("File %s appended.\n", file_src);
            puts("Next file (empty line to quit):");
        }
    }
    printf("Done. %d files appended.\n", files);
    fclose(fa);
    
    return 0;
}

void append(FILE *source, FILE *dest)
{
    size_t bytes;
    static char temp[BUFSIZE]; // allocate once

    while ((bytes = fread(temp,sizeof(char),BUFSIZE,source)) > 0)
        fwrite(temp, sizeof (char), bytes, dest);
}