[cs631apue] [CS631] doubt on dup2
Jan Schaumann
jschauma at stevens.edu
Mon Nov 6 15:30:07 EST 2017
Jeevanandha Ramanathan <jramana1 at stevens.edu> wrote:
> I am not getting the output redirected to the file. Instead it's just
> printing on the screen.
You're duplicating your open file descriptor onto stdout.
Try the other way around:
--- dupdemo2.c.orig 2017-11-06 15:29:24.000000000 -0500
+++ dupdemo2.c 2017-11-06 15:27:37.000000000 -0500
@@ -10,7 +10,7 @@
perror("unable to open the file");
exit(1);
}
- if((r = dup2(STDOUT_FILENO, file))!=file){
+ if((r = dup2(file, STDOUT_FILENO))!=STDOUT_FILENO){
perror("unable to dupe the stdout to file");
}
-Jan
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