Need to convert Binary files to ascii

UNIX for Advanced & Expert Users
1

Dear Experts
I need to read a binary file. I know for example in byte number 3801-3804 there is a 4 byte number embeded. Is there a way to extract this number from this file and then convert it to ascii via unix??
Your help would be highly appreciated.
Very Best Regards
Reza

2

od will jump to an offset with the -j <offset> qualifier.
The -t u4 will tell od to format the output as an unsigned decimal.

You need to check your od man page because I think the -t qualifier is not always supported, and may only support 16 bit words, not 32 bit words.

Otherwise compile and try this
cc -o bfile bfile.c
bfile `head -c -n 3404 mybinaryfile`

/* bfile.c */
#include <stdio.h>
#include <string.h>
int main(int argc, char *argv[])
{
     if (*argv[1])
     {
         if(strlen(argv[1])>3403)
         {
                 char  *p=&argv[1][3401];
                 fprintf(stdout,"%d\n",*(int *)p);
         }
      }
      return 0;
}

You are limited in postion in the file to what _POSIX_ARG_MAX is defined to for your system (in limits.h) - Normally it is 4096.

3

"od -t u4" is fairly common. So try:

dd if=datafile bs=1 skip=3800 count=4 | od -t u4

4

Thank you veru much.
It helps me a lot.
Very Best regards
Reza

5

Friends,

I've tried on solaris, but I could n't find ascii

dd if=binaryinputfile bs=1 skip=3800 count=4 | od -t u4

output :

INDBU3:/usr/users/FTAMUSER/kk $
dd if=SMP20041006173649188151 bs=1 skip=3800 count=4 | od -t u4
4+0 records in
4+0 records out
0000000 0000000000
0000004

Pls help me to convert binary to ascii on solaris.

Thanks
Krishna

6

Krishna,

The above command will work only if:

  1. In the binary file, there is a 4 byte number embeded in bytes 3801-3804.

And remember, it will just give you the Integer present at that location. It won't convert the binary file into text file.