File not deleted in C

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I tried to delete the contains of a file ...but not deletetd

C++

unsigned char buffer[64];	// buffer may be any size
FILE *fp = fopen("image.pgm", "rb";);
FILE *pFile;
char *filename="text";
int ret;
int numread;
 pFile=fopen(filename,"wb");
while (!feof(fp))  // repeat until reached end of file

{
	
    int index;	// index into the buffer
    numread = fread(buffer, sizeof(unsigned char), 64, fp);
    if (numread == 0)
        break;  // no data left to read
    for (index = 0; index < numread; ++index)
    {
        // process each byte of the buffer
        char b = buffer[index];	// b contains the value of the current byte
        printf("byte %d: %c", index, b);
		fprintf(pFile,"%c",b);
    }
	fclose (pFile);
	ret = remove(filename);

   if(ret == 0) 
   {
      printf("\n File deleted successfully");
   }
   else 
   {
      printf("\n Error: unable to delete the file");
   }
}

What I have tried:

C++

unsigned char buffer[64];	// buffer may be any size
FILE *fp = fopen(image.pgm,rb);
FILE *pFile;
char *filename="text";
int ret;
int numread;

pFile=fopen(filename,"wb");

while (!feof(fp))  // repeat until reached end of file
{
    int index;	// index into the buffer
    numread = fread(buffer, sizeof(unsigned char), 64, fp);
    if (numread == 0)
        break;  // no data left to read
    for (index = 0; index < numread; ++index)
    {
        // process each byte of the buffer
        char b = buffer[index];	// b contains the value of the current byte
        printf("byte %d: %c", index, b);
        fprintf(pFile,"%c";,b);
    }
	fclose (pFile);
	ret = remove(filename);

   if(ret == 0) 
   {
      printf("\n File deleted successfully");
   }
   else 
   {
      printf("\n Error: unable to delete the file");
   }

Posted 24-Oct-16 3:43am

yagami_md

Updated 24-Oct-16 5:07am

Leo Chapiro

v2

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Jochen Arndt · Accepted Answer · 2016-10-24T04:48:00

You are trying to delete a file that has just been created (why?).

If that fails, the file has probably not been created (does not exist).
But you don't know that because you are not checking if opening it was successful (pFile not NULL).

So you should check that first (and check also if the input file has been opened):

C++

#include <errno.h> /* for perror() and/or errno */

FILE *fp = fopen(image.pgm,rb);
if (NULL == fp)
{
    perror("Failed to open input file");
    return;
}
char *filename = "text";
FILE pFile = fopen(filename,"wb");
if (NULL == pFile)
{
    perror("Failed to open output file");
    fclose(fp);
    return;
}
/* ... */
if (remove(filename))
{
    perror("Failed to delete output file");
    return;
}
</errno.h>

A possible reason for failure are insufficient access rights (you did not specify a path so that the file will be created in the current working directory).

OriginalGriff · Accepted Answer · 2016-10-24T04:08:00

Solution 1

Start by finding out why the system didn't remove it. remove returns -1 if it has a problem, and sets errno with the error code, so start by looking at that: strerror[^] may help you by converting it to a readable string.

When you know why, it should be fairly obvious what the problem is.

Posted 24-Oct-16 4:08am

OriginalGriff