Opening a file in c programming in xcode 6 - c

Question

#include <stdio.h>
#include <stdlib.h>
int main(int argc, char *argv[])
{
int ch; //place to store each character as read
FILE *fp;
unsigned long count = 0;
if (argc != 2)
{
printf("Usage: %s filename\n", argv[0]);
exit(EXIT_FAILURE);
}
if ((fp = fopen(argv[1], "r")) == NULL)
{
printf("Can't open %s\n", argv[1]);
exit(EXIT_FAILURE);
}
while ((ch = getc(fp)) != EOF)
{
putc(ch,stdout); // same as putchar(ch);
count++;
}
fclose(fp);
printf("File %s has %lu characters\n", argv[1], count);
return 0;
}
The result running this program is:
Usage: /Users/huangweijun/Library/Developer/Xcode/DerivedData/input-hhjvfzwnywskidbyoxavtgvmoffb/Build/Products/Debug/input filename
I don't know which step is wrong.

Answer 1

The problem is you need to pass exaclty 1 argument to your program on invokation, to achieve that in XCode you neet to go to thes menu
Product -> Edit Scheme... -> Run -> Arguments
and there you will see Arguments Passed On Launch click the plus sign, and then add a file name, the path to the file you wish to open.
Or you can ask the user for a file name like this
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(int argc, char *argv[])
{
int ch; //place to store each character as read
FILE *fp;
unsigned long count = 0;
const char *filename;
char buffer[128];
filename = NULL;
if (argc != 2)
{
size_t length;
printf("Enter the file name > ");
if (fgets(buffer, sizeof(buffer), stdin) == NULL)
return -1; // error or end of file sent to the terminal
length = strlen(buffer);
if (buffer[length - 1] == '\n') // remove the traling '\n' add by fgets
buffer[length - 1] = '\0';
filename = buffer;
}
else
filename = argv[1];
if ((fp = fopen(filename, "r")) == NULL)
{
printf("Can't open %s\n", filename);
exit(EXIT_FAILURE);
}
while ((ch = getc(fp)) != EOF)
{
putc(ch,stdout); // same as putchar(ch);
count++;
}
fclose(fp);
printf("File %s has %lu characters\n", filename, count);
return 0;
}

Answer 2

You are not providing enough command line arguments. To provide an input file in xcode, you can go to the Product Menu -> Scheme -> Edit Scheme option.... at this point you can pass in the path to the file you wish to use as input
Your program is working as it is supposed to. You are not providing the command line argument and it is telling you so
The Screen for adding arguments in xcode looks like what I am showing below. You get to this screen, using the menu options described above, click the plus button, then added the path to the input file

Answer 3

There's nothing wrong. Read the code, especially this part:
if (argc != 2)
{
printf("Usage: %s filename\n", argv[0]);
exit(EXIT_FAILURE);
}
If the number of command-line arguments is not equal to 2, print out some usage information then exit. So you need to invoke the program with a single command-line argument.
Note that although it compares to the value 2, the program needs only 1 argument, since the program name itself counts as the first argument, i.e. argv[0].

Answer 4

Product -> Edit Scheme... -> Run -> Arguments
in "Arguments Passed On Launch" click the plus sign, and then add an absolute file name, the path to the file you wish to open.
***If your folder names, in your absolute path, have spaces THIS WILL NOT WORK!. Therefore open up terminal, drag and drop your file in the terminal window then copy the absolute path (from the terminal window of course) and paste it in "Arguments Passed On Launch" section (as explained above).