Q60336: PRB: fscanf() Fails to Read Consecutive Lines

Article: Q60336
Product(s): Microsoft C Compiler
Version(s): MS-DOS:5.1,6.0,6.00a,6.00ax,7.0;WINDOWS:1.0,1.5;WINDOWS NT:1.0,2.0,2.1,4.0,4.1,4.2,5.0
Operating System(s): 
Keyword(s): kbcode kbCRT kbVC kbVC100 kbVC150 kbVC200 kbVC210 kbVC400 kbVC410 kbVC420 kbVC500 kbVC6
Last Modified: 25-JUL-2001

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The information in this article applies to:

- The C Run-Time (CRT), included with:
   - Microsoft C for MS-DOS, versions 5.1, 6.0, 6.0a, 6.0ax 
   - Microsoft C/C++ for MS-DOS, version 7.0 
   - Microsoft Visual C++, versions 1.0, 1.5 
   - Microsoft C for OS/2, versions 5.1, 6.0, 6.0a 
   - Microsoft Visual C++, 32-bit Editions, versions 1.0, 2.0, 2.1, 4.0, 4.1, 4.2, 5.0, 6.0 
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 4.2 
   - Microsoft Visual C++, 32-bit Professional Edition, version 4.2 
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 5.0 
   - Microsoft Visual C++, 32-bit Professional Edition, version 5.0 
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 6.0 
   - Microsoft Visual C++, 32-bit Professional Edition, version 6.0 
   - Microsoft Visual C++, 32-bit Learning Edition, version 6.0 
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SYMPTOMS
========

When a file is open in text mode, an attempt to read lines of text with the
fscanf() function may fail and only one line of text is read from the file.

CAUSE
=====

The delimeter is set to "[^\n]". The fscanf() function reads up to but does not
include the delimiting character. Therefore, the file stream stops at the first
'\n' in the file. Subsequent fscanf() calls fail because the file pointer
remains at the delimiting character and fscanf() cannot advance the function
pointer past it.

RESOLUTION
==========

Use one of the following two methods to move the file pointer past the
delimiting character:

- Update the code to use the following fscanf() call:

        fscanf(stream, "%[^\n]%*c", line)

  The "%*c" format specifier reads one character from the input stream but does
  not assign it to any of the parameters in the fscanf function call.

- Call fgetc() after the fscanf() call to move the file pointer beyond the '\n'
  character.

MORE INFORMATION
================

The following code demonstrates this problem. It should read and print lines
from a text file until it reaches EOF. However, it reads only the first line
from the file. Since the end of file character has not been found, the example
shown below will run in an infinite loop if the file stream contains a "\n"
character.

Sample Code
-----------

  FILE *stream;
  char line[80];

  while ((fscanf(stream, "%[^\n]", line)) != EOF )
  {
     printf("Line = %s \n",line);
  }

The following code demonstrates the second method above to work around this
problem:

  FILE *stream;
  char line[80];

  while ((fscanf(stream, "%[^\n]", line)) != EOF)
  {
     fgetc(stream);    // Reads in '\n' character and moves file
                       // stream past delimiting character
     printf("Line = %s \n", line);
  }

Additional query words: 8.0 9.0 10.0 11.0

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Keywords          : kbcode kbCRT kbVC kbVC100 kbVC150 kbVC200 kbVC210 kbVC400 kbVC410 kbVC420 kbVC500 kbVC600 
Technology        : kbVCsearch kbAudDeveloper kbCRT
Version           : MS-DOS:5.1,6.0,6.00a,6.00ax,7.0;WINDOWS:1.0,1.5;WINDOWS NT:1.0,2.0,2.1,4.0,4.1,4.2,5.0
Issue type        : kbprb

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