使用 C 和 fopen() 在 Xcode 中打开 .txt 文件

Question

I can't seem to get a file to open in C. What am I doing wrong? The file is in the same directory as the .c file and I think I got all the syntax. Here is a screenshot:

The output says that the file pointer is NULL.

Answer 1

For that to work, the "test.txt" has to be in the same directory as the compiled binary (which xcode may not be putting in the same directory as main.c - it may be in Products? I'm not so sure with xcode). Try giving the fully-qualified pathname to test.txt in the call to fopen.

Answer 2

If fopen fails, fp is set to NULL and errno is set according. To see why, try:

#include <stdio.h>
#include <string.h>
#include <errno.h>

int
main( void )
{
  int status = EXIT_SUCCESS;
  FILE *fp = fopen(“test.txt”, “r”);
  if( fp == NULL )
  {
    fprintf( stderr, “Errno %d, Error %s, opening text.txt for reading.\n”, errno, strerror(errno));
    status = errno;
  }

  // Do something with fp...
  return(status);
}

To open the file from any directory, pass the file name in argv, check for arguments and use that parameter to main as the file name( pref. after copying to a dedicated variable).