Segmentation fault when I fopen - c

Question

I'm new to C file management . My teacher wanted as a homework to create a functon that copy from a source file to destination file . I created but it gives me errors all the time : Segmentation Fault .
void source_to_destination(FILE *source , FILE *destination)
{
char name_source[10], name_destination[10],line[100];
memset(line,0,sizeof(line));
memset(name_source,0,sizeof(name_source));
memset(name_destination,0,sizeof(name_destination));
read_name_file(name_source);
read_name_file(name_destination);
source = fopen(name_source,"r");
destination = fopen(name_destination,"w");
while(fgets(line,sizeof(line),source) != NULL)
{
fputs(line,destination);
}
}

Answer 1

When copying data from one file to another, reading and writing in binary is preferred. There are a number of reasons that reading with line-oriented input functions such as fgets or getline will fail to properly read all characters in a file. Text output functions suffer similar shortcomings (e.g. attempting to write characters outside the printable range or characters that have alternate meaning as ASCII)
Reading and writing from a file in binary mode using fread and fwrite is not any more difficult than using fgets and fputs. However, using fread and fwrite you are guaranteed a correct and accurate copy of your data by avoiding the pitfalls inherent in attempting a general file copy in text mode.
If you know there is nothing but text contained in your source file, then there is nothing wrong with copying it in text mode. That just means you will have to write another function to handle files that are not text. (and generally you don't see different copy routines based on file contents). Reading and writing in binary eliminates all of these considerations.
The following is a short example of a filecopy function that will read all bytes in a file into a buffer and then write the contents of the buffer to your destination file. (a buffered read/write is generally much more efficient and you can easily adjust the buffer size by adjusting MAXS) The function returns the number of bytes copied on success, -1 otherwise. Look it over and let me know if you have any questions:
#include <stdio.h>
#include <stdlib.h>
#define MAXS 256
int filecopy (char *source, char *dest);
int main (int argc, char **argv) {
if (argc < 3) { /* validate 2 arguments given */
fprintf (stderr, "usage: %s file1 file2\n", argv[0]);
return 1;
}
int filesize = 0;
if ((filesize = filecopy (argv[1], argv[2])) == -1) {
fprintf (stderr, "error: filecopy failed.\n");
return 1;
}
printf ("\n copied '%s' -> '%s' ('%d' bytes)\n\n",
argv[1], argv[2], filesize);
return 0;
}
int filecopy (char *source, char *dest)
{
char *buf = NULL; /* buffer used to read MAXS bytes from file */
size_t nbytes = 0; /* number of bytes read from file */
size_t idx = 0; /* file index (length) */
FILE *fp = fopen (source, "r"); /* stream pointer */
if (!fp) { /* open source for reading */
fprintf (stderr, "error: file open failed '%s'.\n", source);
return -1;
}
/* allocate MAXS size read buf initially */
if (!(buf = calloc (MAXS, sizeof *buf))) {
fprintf (stderr, "error: virtual memory exhausted.\n");
return -1;
}
/* while data read MAXS *buf from file - realloc for next read */
while ((nbytes = fread (buf+idx, sizeof *buf, MAXS, fp)))
{
idx += nbytes; /* update total bytes read */
if (nbytes < MAXS) break; /* end-of-file reached */
/* full read - realloc for next */
void *tmp;
if (!(tmp = realloc (buf, (idx + nbytes) * sizeof *buf))) {
fprintf (stderr, "error: virtual memory exhausted.\n");
exit (EXIT_FAILURE);
}
buf = tmp;
}
fclose (fp); /* close input stream */
if (!(fp = fopen (dest, "w+b"))) { /* open output stream */
fprintf (stderr, "error: file open failed '%s'.\n", dest);
exit (EXIT_FAILURE);
}
fwrite (buf, sizeof *buf, idx, fp);
fclose (fp); /* close output stream */
free (buf);
return (int)idx;
}
Compile
gcc -Wall -Wextra -O3 -o bin/filecopy_simple filecopy_simple.c
Input File (binary)
-rw-r--r-- 1 david david 66672 Nov 19 13:17 acarsout2.bin
Use/Output
$ ./bin/filecopy_simple dat/acarsout2.bin dat/acarsout3.bin
copied 'dat/acarsout2.bin' -> 'dat/acarsout3.bin' ('66672' bytes)
Verification
$ ls -al acarsout[23]*
-rw-r--r-- 1 david david 66672 Nov 19 13:17 acarsout2.bin
-rw-r--r-- 1 david david 66672 Dec 13 14:51 acarsout3.bin
$ diff dat/acarsout2.bin dat/acarsout3.bin
$

Answer 2

The following code
compiles cleanly
performs the desire operation (copy a file)
perform appropriate error checking
is getting the file names from the command line
You will need to modify this to get the file names via your existing functions
always cleans up after itself including closing open files
demonstrates how to pass the FILE* variables --into-- the function
the sub function prototype, etc will need to be modified
if you want to open the files in the sub function
then have main() close them.
Here is a suggested method of performing the desired operation
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#define MAX_LINE_LENGTH (256)
// prototypes
void source_to_destination(FILE *source , FILE *destination);
int main( int argc, char * argv[] )
{
if( 3 != argc )
{ // not correct number of command line parameters
fprintf( stderr, "USAGE: %s <sourceFili> <destinationFile>\n", argv[0]);
exit( EXIT_FAILURE );
}
// implied else, correct number of arguments
FILE *fp_in = NULL;
if( NULL == (fp_in = fopen( argv[1], "r") ) )
{ // then fopen failed
fprintf( stderr, "fopen for input file: %s failed due to %s\n", argv[1], strerror(errno) );
exit( EXIT_FAILURE );
}
// implied else, fopen input file successful
FILE *fp_out = NULL;
if( NULL == (fp_out = fopen( argv[2], "w") ) )
{ // then fopen failed
fprintf( stderr, "fopen for output file: %s failed due to %s\n", argv[2], strerror(errno) );
fclose( fp_in ); // cleanup
exit( EXIT_FAILURE );
}
// implied else, fopen output file successful
source_to_destination( fp_in, fp_out );
fclose( fp_in );
fclose( fp_out );
return 0;
} // end function: main
void source_to_destination(FILE *source , FILE *destination)
{
char line[ MAX_LINE_LENGTH ];
while(fgets(line,sizeof(line),source) )
{
if( EOF == fputs(line,destination) )
{ // then fputs failed
fprintf( stderr, "fputs to output file failed due to %s\n", strerror(errno) );
fclose( source );
fclose( destination );
exit( EXIT_FAILURE );
}
}
} // end function: source_to_destination