open files as binary...

[adfm]

Hello everybody

I'm porting a c/c++ applications from windows to linux, and I'm having problems with the open() function. I opened the files as binary in windows, but in linux I cannot do that. The O_BINARY flag does not exist... :o

When I started checking out why, I found a nice bit of information on the fopen() function that rocked my world...

(...)
The mode string can also include the letter ``b'' either as a last character or as a character between the characters in any of the two-character strings described above. This is strictly for compatibility with C89 and has no effect; the ``b'' is ignored on all POSIX conforming systems, including Linux.
(...)

I have a quite large application and I'm having some problems because the files are opened as text and the read fails sometimes (other times it dosn't . don't know why )

Any ideas how I can give this problem a twist?

well, thanks for all the help I hope is coming my way

André

[Franklin52]

What problems? How do you read the files? Post some snippet of your code.
Here an example how you can read a textfile:

int main()
{
	FILE *inp;
	char readbuf[256];

	inp = fopen("textfile", "r");

	while(fgets(readbuf, 255, inp) != NULL) {
		printf("%s\n", readbuf);
	}

	fclose(inp);
	return(0);
}

Note that in DOS files a line end with CRLF instead of LF.
The following command convert a DOS file to Linux format:

sed 's/^M$//' input.txt > output.txt

Press Ctrl-V then Ctrl-M to get the ^M.

Regards

[Franklin52]

I misread your question, this is an example of reading and writing a binary file:

#include <stdio.h>
#include <fcntl.h>

#define PERMS 0666

int main (int argc, char *argv[])
{
	int inp, outp;
	char readbuf[BUFSIZ];
	int n;

	inp = open("bin_file1", O_RDONLY, 0);
	outp = creat("bin_file2", PERMS);	

	while((n = read(inp, readbuf, BUFSIZ)) > 0) {
		if(write(outp, readbuf,n) != n)
		    perror("Write");
	}

  	return(0);
}

Regards

[adfm]

Franklin52

thanks for your replies but I'm doing the same thing as in you example code.

I defined the flags as

i

nt flags[4][3] =     
       {
       {O_RDWR|O_CREAT,S_IREAD|S_IWRITE,SH_DENYRW|S_IRWXU},
       {O_RDONLY,S_IREAD,SH_DENYNO|S_IRWXU},                           {O_WRONLY|O_TRUNC|O_CREAT,S_IREAD|S_IWRITE,SH_DENYWR|S_IRWXU},
 {O_WRONLY|O_APPEND|O_CREAT,S_IREAD|S_IWRITE,SH_DENYWR|S_IRWXU}
        };

and used open

handle=open(nome,flags[my_mode][0],flags[my_mode][2],flags[my_mode][1]);

As much as I've read so far, in Linux all files are handled as text and there is no support for binary files... in this page http://djgpp.linux-mirror.org/v2faq/faq9_4.html It is stated that:

Note that the above distinction between binary and text files is written into the ANSI/ISO C standard, so programs that rely on the Unix behavior whereby there's no such distinction, are strictly speaking not portable.

and adding to all my problems

Well the difference is that text files contain lines (or records) of text
 and each of these has an end-of-line marker automatically appended
 to the end of it whenever you indicate that you have reached the
 end of a line. There is an end of line at the end of the text written
 with the C fwrite() function or in C++ when you <<endl. Binary files
 are not broken up into separate lines or records so the end-of line
 marker is not written when writing to a binary file.

Reading from a text file or binary file is different too as a text file is
automatically broken up into separate records as it read in based on
the location of the end-of-line markers.

So my problem persists(?) how do handle this...

regards

[Franklin52]

Your open statement doesn't use proper arguments, try:

handle=open(nome, O_RDONLY, 0);

To read random from the file you can use the functions fseek, ftell, rewind, fgetpos, fsetpos.
Check the man pages.

Regards

[tpl]

welcome to the forum

> the files are opened *as*text*

the files are opened--text, binary, whatever--it's all the same in *nix

quoting Kernighan & Ritchie: "...our fopen does not recognize the "b"
that signals binary access, since that is meaningless on UNIX
systems..." K&R,2nd ed'n,p.178

> the read fails sometimes...

well, I think you'll have to look elsewhere for your problem.