What I want to do
redirect stdout and stderr to one or more files from inside c++
Why I need it
I am using an external, pr
In addition to afr0ck answer of freopen() I want to say that while using freopen()
we should be careful. Once a stream like stdout
or stdin
is reopened with assigning the new destination(here the 'output.txt' file) always it remains for a program unless it has been explicitly change.
freopen("output.txt", "a", stdout);
Here the standard output stream stdout
is reopened and assigned with the 'output.txt' file. After that whenever we use printf()
or any other stdout
stream like - putchar()
then every output will goes to the 'output.txt'. To get back the default behavior (that is printing the output in console/terminal) of printf()
or putchar()
we can use the following line of code -
freopen("/dev/tty", "w", stdout);
freopen("CON", "w", stdout);
See the code example below -
#include
int main() {
printf("No#1. This line goes to terminal/console\n");
freopen("output.txt", "a", stdout);
printf("No#2. This line goes to the \"output.txt\" file\n");
printf("No#3. This line aslo goes to the \"output.txt\" file\n");
freopen("/dev/tty", "w", stdout); /*for gcc, diffrent linux distro eg. - ubuntu*/
//freopen("CON", "w", stdout); /*Mingw C++; Windows*/
printf("No#4. This line again goes to terminal/console\n");
}
This code generate a 'output.txt' file in your current directory and the No#2 and No#3 will be printed in the 'output.txt' file.
Thanks