Question

C Language Programming.

Using the program below - When executing on the command line only this program name, the program will accept keyboard input and display such until the user does control+break to exit the program.

The new code should within only this case situation

“if (argc == 1){ /* no args; copy standard input */”

Replace line #20 “filecopy(stdin, stdout);” with new code.

Open read a text file “7NoInputFileResponse.txt” that contains a message “There were no arguments on the command line to be tested for file open.”

Append that message to a file “7Error_Log_File.txt” . ?newline

Remember to be using fprintf using stderr using return using exit statements. Test for file existence, test 7NoInputFileResponse.txt file not null (if null use alternate text string “99 error unknown ” from within the program), existence of 7Error_Log_File.txt otherwise display such message using fprintf stderr and exit.

#include <stdio.h>
#include <stdlib.h> /*needed for stderr and exit */
/* cat: concatenate files, version 2 */

/* filecopy: copy file ifp to file ofp */
void filecopy(FILE *ifp, FILE *ofp) /* pointer to input file, output file */
{
   int c;
   while ((c = getc(ifp)) != EOF)
      putc(c, ofp);
}

int main(int argc, char *argv[])
{
   FILE *fp;
   void filecopy(FILE *, FILE *);
   char *prog = argv[0];  /* this program exe name as source of an error */
   
   if (argc == 1){ /* no args; copy standard input */
      filecopy(stdin, stdout);  /* keyboard_input is repeated as display_output, ctrl_break to exit */
   }
   else
      while (--argc > 0)
         if (( fp = fopen(*++argv, "r")) == NULL) { /* pointer to next command line file */
            fprintf(stderr, "%s: can not open %s\n", prog, *argv);
            exit(1);  /* determined by programmer return value for error type #1 */
         } else {
            filecopy(fp, stdout);
            fclose (fp);
         }
         
   if(ferror(stdout)) {
      fprintf(stderr, "%s: error writing stdout\n", prog);
      exit(2);  /* determined by programmer return value for error type #2 */
   }
   
   exit(0);  /* determined by programmer return value for error type #0, success */
}

Answer 1

//do comment if any problem arises

//modified code has been highlighted

#include <stdio.h>

#include <stdlib.h> /*needed for stderr and exit */

/* cat: concatenate files, version 2 */

/* filecopy: copy file ifp to file ofp */

void filecopy(FILE *ifp, FILE *ofp) /* pointer to input file, output file */

{

int c;

while ((c = getc(ifp)) != EOF)

putc(c, ofp);

}

int main(int argc, char *argv[])

{

FILE *fp;

void filecopy(FILE *, FILE *);

char *prog = argv[0]; /* this program exe name as source of an error */

if (argc == 1)

{ /* no args; copy standard input */

//open input file

FILE *infile = fopen("7NoInputFileResponse.txt", "r");

//error message

char error_message[100] = "99 error unknown";

//open output file

FILE *outfile = fopen("7Error_Log_File.txt", "a");

//if file oppened successfuly then read into error message

if (infile == NULL)

{

//if outfile is opened successfully

if (outfile != NULL)

{

fprintf(outfile, error_message);

fprintf(outfile, "\n");

exit(0);

}

}

//if outputfile doesn't open successfuly

if (outfile == NULL)

{

//print error message to stderr

fprintf(stderr, error_message);

//exit

exit(0);

}

//copy contents of input file to output file

filecopy(infile, outfile);

//append newline

fprintf(outfile, "\n");

fclose(infile);

fclose(outfile);

}

else

while (--argc > 0)

if ((fp = fopen(*++argv, "r")) == NULL)

{ /* pointer to next command line file */

fprintf(stderr, "%s: can not open %s\n", prog, *argv);

exit(1); /* determined by programmer return value for error type #1 */

}

else

{

filecopy(fp, stdout);

fclose(fp);

}

if (ferror(stdout))

{

fprintf(stderr, "%s: error writing stdout\n", prog);

exit(2); /* determined by programmer return value for error type #2 */

}

exit(0); /* determined by programmer return value for error type #0, success */

}

Output:

ran this program 2 times first when input file is available and second when input file is deleted

these are contents of output file: