Merging a list of files into another - c

Question

I'm trying to make a program that takes a series of files and copies them into another one.
for example
./foobar arch1.txt arch2.txt arch3.txt
must create arch3.txt with the contents of arch1.txt arch2.txt, archN.txt.
This is my code:
#include <stdio.h>
#include <stdlib.h>
void usage (char *argv[], int code)
{
printf("usage: %s [<file> <out_file>] \n", argv[0]);
exit(code);
}
void copyFile (FILE *ifp, FILE *ofp)
{
int c;
while ((c = fgetc(ifp)) != EOF)
fputc(c, ofp);
}
int main(int argc, char *argv[])
{
system ("clear");
FILE *fp, *fp2;
if (argc < 3)
usage(argv, EXIT_FAILURE);
else
if ((fp2 = fopen(argv[argc-1], "w")) == NULL) {
printf("Can't open file to write: %s\n", *argv);
exit(EXIT_FAILURE);
}
while(--argc > 0)
printf("%d",argc);
if ((fp = fopen(*++argv, "r")) == NULL) {
printf("Can't open file: %s\n", *argv);
exit(EXIT_FAILURE);
}
else {
copyFile(fp, fp2);
fclose(fp);
fclose(fp2);
}
return 0;
}
My ouput:
Can't open file to write: ./foobar

Answer 1

That's because you're using *argv for the filename parameter in fopen(). It should be argv[argc - 1].

Answer 2

*argv is not the first argument, but rather the path of the executable.
Increment argv once before using it directly:
argv++ ;
if ((fp2 = fopen(argv[argc-1], "w")) == NULL) {
or perhaps better use array indexing and start from argv[1].

Answer 3

I fixed it. It's not pretty but it works now.
#include <stdio.h>
#include <stdlib.h>
void usage (char *argv[], int code)
{
printf("usage: %s [<file> <out_file>] \n", argv[0]);
exit(code);
}
void copyFile (FILE *ifp, FILE *ofp)
{
int c;
while ((c = fgetc(ifp)) != EOF)
fputc(c, ofp);
}
int main(int argc, char *argv[])
{
FILE *f_read, *f_write;
int i;
if (argc < 3)
usage(argv, EXIT_FAILURE);
if ((f_write = fopen(argv[argc-1], "w")) == NULL) {
printf("Can't write in: %s\n", argv[argc-1]);
exit(EXIT_FAILURE);
}
for (i = 1; i < argc-1; ++i)
{
if ((f_read = fopen(argv[i], "r")) == NULL) {
printf("Can't open file: %s\n", argv[i]);
exit(EXIT_FAILURE);
}
else
copyFile(f_read, f_write);
}
fclose(f_read);
fclose(f_write);
return 0;
}