open.c

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/* OPEN.C - Routine for opening file that might be stdin/stdout. */
//打开标准输入输出文件的程序
/* Copyright (c) 2001 by Radford M. Neal 
 *
 * Permission is granted for anyone to copy, use, or modify this program 
 * for purposes of research or education, provided this copyright notice 
 * is retained, and note is made of any changes that have been made. 
 *
 * This program is distributed without any warranty, express or implied.
 * As this program was written for research purposes only, it has not been
 * tested to the degree that would be advisable in any important application.
 * All use of this program is entirely at the user's own risk.
 */

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

#include "open.h"


/* OPEN A FILE THAT MIGHT BE STANDARD INPUT OR OUTPUT.  If the file name
   given is "-", this procedure just returns stdin or stdout, depending on
   whether the mode is for reading or writing.  Otherwise, fopen is called. 
*/

FILE *open_file_std
( char *fname,	/* Name of file to open, or "-" for stdin/stdout要打开的文件*/
  char *mode	/* Mode for opening: eg, "r" or "w"打开方式 */
)
{ 
  if (strcmp(fname,"-")==0)
  { switch (mode[0])
    { case 'r': 
      { return stdin;
      }
      case 'w': 
      { return stdout;
      }
      default:  
      { fprintf(stderr,"Bad mode passed to open_file_std: %s\n",mode);
        exit(1);
      }
    }
  }
  else
  { return fopen(fname,mode);
  }
}