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i am programming C on windows. i encountered this problem while trying to read a .tar.gz file.

the file looks like (opened with notepad++): enter image description here

and the code i used to read is as follow:

iFile = fopen("my.tar.gz", "r");
while ((oneChar = fgetc(iFile)) != EOF) {
        printf("%c", oneChar);
}

the following figure shows the result of my program: enter image description here

The problem I have is, the result only has several lines while the original file has thousands of lines (6310 lines, as you can see). My guess is that the .tar.gz file contains some strange characters (like an EOF in the middle of the file?).

My question is why notepad++ can display the whole file while my program can not. And is there a solution to this problem?

Eumaa
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  • Please post a complete example. In particular, it would be interesting how you declare `oneChar`. It should be `int`. It might also be more helpful to print the file in hex and compare with the output of [`hexdump`](http://manpages.debian.org/cgi-bin/man.cgi?query=hexdump&sektion=1), if you have that. The awkward characters in a binary file may well cause your terminal to overwrite itself. Finally, open the file in `"rb"` mode. – 5gon12eder Jan 08 '16 at 05:56
  • No problem there. I did declared: int oneChar; – Eumaa Jan 08 '16 at 05:59
  • **Why** do you want to open and read a `.tar.gz` file? It is very likely to be useless. And please **edit your question** don't comment it ... BTW, your question is operating system specific, so please tag it with your OS related tag. – Basile Starynkevitch Jan 08 '16 at 06:28

2 Answers2

4

A .tar.gz file is conventionally a gnu-zipped compression of some tar archive. It is of course a binary file (any '\n' or '\r' inside it does not delimit lines, and '\0' may appear inside), so you need to open it with

 iFile = fopen("my.tar.gz", "rb");
 if (!iFile) { perror("my.tar.gz"); exit(EXIT_FAILURE); }

Also, feof(iFile) is valid only after some <stdio.h> input operation so while(!feof(iFile)) is wrong just after the fopen...

But that won't help you extracting any files from the archive.

So you need to first uncompress that file then extract or list the relevant archives files in it.

You could find libraries (and command executables) for both the uncompression (zlib library, gunzip or zcat commands) and the archive extraction (libarchive library, or libtar, or tar command) steps.

If your operating system provides it, you could consider using appropriately the popen function.

BTW using putchar(oneChar) is shorter, simpler and faster than printf("%c", oneChar) ....

Basile Starynkevitch
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3

Usually the file ending tar.gz is a compresses tar file )a binary file). Therefore I would suggest you use popen (http://linux.die.net/man/3/popen) instead of fopen to open the file using a command.

i.e.

iFile = popen("zcat my.tar.gz | tar xf -", "r");
Ed Heal
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  • I'm not positive, but I believe the OP is on windows. I don't know if there is a `zcat.exe`, but the *7zip* command line executable `7z.exe` may provide similar capabilities with `-tgzip` option. You would just have to confirm how to redirect the output to `stdout` – David C. Rankin Jan 08 '16 at 06:35