/* * File: linecopy.c * ---------------- * This program copies one file to another using line I/O. */#include <stdio.h>#include "genlib.h"#include "simpio.h"/* * Constants * --------- * MaxLine -- Size of the buffer used in CopyFile */#define MaxLine 100/* Private function prototypes */static void CopyFile(FILE *infile, FILE *outfile);static FILE *OpenUserFile(string prompt, string mode);/* Main program */main(){    FILE *infile, *outfile;    printf("This program copies one file to another.\n");    infile = OpenUserFile("Old file: ", "r");    outfile = OpenUserFile("New file: ", "w");    CopyFile(infile, outfile);    fclose(infile);    fclose(outfile);}/* * Function: CopyFile * Usage: CopyFile(infile, outfile); * --------------------------------- * This function copies the contents of infile to outfile.  The * client is responsible for opening these files before calling * CopyFile and for closing them afterward.  This implementation * uses line I/O to perform the copy.  Note that this approach * works correctly even if the file contains a line longer than * MaxLine; long lines are simply copied in pieces. */static void CopyFile(FILE *infile, FILE *outfile){    char buffer[MaxLine];    while (fgets(buffer, MaxLine, infile) != NULL) {        fputs(buffer, outfile);    }}/* * Function: OpenUserFile * Usage: fileptr = OpenUserFile(prompt, mode); * -------------------------------------------- * This function prompts the user for a file name using the * prompt string supplied by the user and then attempts to * open that file with the specified mode.  If the file is * opened successfully, OpenUserFile returns the appropriate * file pointer.  If the open operation fails, the user is * informed of the failure and given an opportunity to enter * another file name. */static FILE *OpenUserFile(string prompt, string mode){    string filename;    FILE *result;    while (TRUE) {        printf("%s", prompt);        filename = GetLine();        result = fopen(filename, mode);        if (result != NULL) break;        printf("Can't open the file \"%s\"\n", filename);    }    return (result);}