freopen, fclose and stdout

[Alex Vinokur]

Hi,


freopen closes stdout, but it seems that fclose doesn't restore it (see sample below).

How can one print to stdout after using freopen?


========= C code : File foo.c : BEGIN =========
#include <stdio.h>
#include <assert.h>

#define FILE_NAME "foobar"

int main ()
{
FILE* out_fp;
int rc;

remove (FILE_NAME);

printf ( "printf-1\n");

out_fp = freopen (FILE_NAME, "a", stdout);
assert (out_fp);

printf ("printf-2\n");
fprintf (out_fp, "fprintf(out_fp)\n");

rc = fclose (out_fp);
assert (!rc);

printf ("printf-3\n"); // Problematic printf

return 0;
}
========= C code : File foo.c : END ===========


========= Compilation & Run : BEGIN =========

$ gcc -v
[---omitted---]
gcc version 3.3.1 (cygming special)

$ gcc -W -Wall foo.c

$ a
printf-1
// printf-3 missing

$ cat foobar
printf-2
fprintf(out_fp)

========= Compilation & Run : END ===========



=====================================
Alex Vinokur
mailto:[email protected]
http://up.to/alexvn
=====================================

 

[Grumble]

freopen closes stdout, but it seems that fclose doesn't restore it (see sample below).

How can one print to stdout after using freopen?

http://www.eskimo.com/~scs/C-faq/q12.34.html

 

[Eric Sosman]

Hi,

freopen closes stdout, but it seems that fclose doesn't restore it (see sample below).

How can one print to stdout after using freopen?

This is Question 12.34 in the comp.lang.c Frequently
Asked Questions (FAQ) list

http://www.eskimo.com/~scs/C-faq/top.html

.... and you're not going to like the answer.

 

[schneidp20]

I couldn't take no for an answer and dug a little deeper. At least for MS systems you can switch back and forth from stdout and redirected stdout:

printf("To Console\n");
f = freopen("out.txt","w",stdout);
printf("redirect to file\n");
f = freopen("CON", "w", stdout);
printf("back to console\n");

Enjoy!
David Schneider

 

[vidyaani]

How to print the stdout after using freopen..

Solution:

you can type these freopen ("/dev/tty", "a", stdout).
before that printf statement which you want to print in the stdout
Is this what you were trying to do