parsing a binary file in C

Question

I am trying to read a binary file for it's content It has two sets of lines for each component Second last character on the first line indicates the type of the component file (^A for assembly and ^B for part) If the type is ^A I need to parse the file specified in next line which starts with name^@

àtype^@^Aà
name^@assembly1

àtype^@^Aà
name^@assembly2

àtype^@^Bà
name^@apart1

àtype^@^Bà
name^@apart2

When I try to parse this file, I can not read past the binary characters in the file. First line contains a binary character (à) so I get an empty line. Second line has ^@ after name, so I only get 'name' and the len is 4. This is my code snippet

FILE *fp;
  char line[256];
  fp = fopen(name, "rb");
  fgets(line, 256, fp);

  printf("line %s\n", line);
  printf("len %d\n\n", strlen(line));

  fgets(line, 256, fp);

  printf("line %s\n", line);
  printf("len %d\n\n", strlen(line));

This is the output

line 
len 0

line name
len 4

My aim is to parse the type of component (^A or ^B) and then get the name of the component. Please help in pointing out how to solve this.

What on earth is a "binary character"? What's a "non-binary character", for that matter? — Kerrek SB
– Kerrek SB, Commented Oct 10, 2011 at 18:57

pmg · Accepted Answer · 2011-10-10 19:03:24Z

5

fgets and most <stdio.h> functions work with text, not binary data.

The "character" ^@ has, I think, the binary value 0, which messes up all the string handling functions.

You need to read character-by-character and/or not use string functions with objects containing embedded zero bytes.

answered Oct 10, 2011 at 19:03

pmg

109k14 gold badges132 silver badges203 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

pmg Over a year ago

Note that fgets reads all the bytes, including the '\0' and the following ones -- but, again, you cannot use string functions on that data. After you read the second line, line[4] is 0 but printf("%s\n", line+5) outputs "assembly1".

vinaym Over a year ago

Thanks pmg. Both the answer and this comment helped.

Collectives™ on Stack Overflow

parsing a binary file in C

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related