I want to redirect output of printf and perror to a file in a C program. Please anyone help me how to do it. I also tried this by the help of system() funtion but it did not work.
For example i want to print the messages below to a file without using fprintf. Even if the file is opened.

fp=fopen("abc.txt","w");

printf("\nHai How are You ?\n");
perror("\n I AM HERE\n");


I want that both the above statements should write into the file abc.txt not at stdout or stderr ie console.
Please help. Thanks

: I want to redirect output of printf and perror to a file in a C program. Please anyone help me how to do it. I also tried this by the help of system() funtion but it did not work.
: For example i want to print the messages below to a file without using fprintf. Even if the file is opened.
:
: fp=fopen("abc.txt","w");
:
: printf("\nHai How are You ?\n");
: perror("\n I AM HERE\n");
:
:
: I want that both the above statements should write into the file abc.txt not at stdout or stderr ie console.
: Please help. Thanks
:
:
Use the freopen function:

stream = freopen( "abc.tct", "w", stdout );

Greets,
Eric Goldstein
http://www.gvh-maatwerk.nl

This message was edited by stober at 2006-5-19 7:46:32

---

: I want to redirect output of printf and perror to a file in a C program. Please anyone help me how to do it. I also tried this by the help of system() funtion but it did not work.
: For example i want to print the messages below to a file without using fprintf. Even if the file is opened.
:
: fp=fopen("abc.txt","w");
:
: printf("\nHai How are You ?\n");
: perror("\n I AM HERE\n");
:
:
: I want that both the above statements should write into the file abc.txt not at stdout or stderr ie console.
: Please help. Thanks
:
:
:


you are using the wrong function.
fprintf(fp,"\nHai How are You ?\n");

perror goes to stderr, not to a file. So you have to call freopen() as previously suggested.
stream = freopen( "abc.tct", "w", stderr );

see the example program here:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vccore98/HTML/_crt_freopen.2c_._wfreopen.asp

: This message was edited by stober at 2006-5-19 7:46:32

---

: : I want to redirect output of printf and perror to a file in a C program. Please anyone help me how to do it. I also tried this by the help of system() funtion but it did not work.
: : For example i want to print the messages below to a file without using fprintf. Even if the file is opened.
: :
: : fp=fopen("abc.txt","w");
: :
: : printf("\nHai How are You ?\n");
: : perror("\n I AM HERE\n");
: :
: :
: : I want that both the above statements should write into the file abc.txt not at stdout or stderr ie console.
: : Please help. Thanks
: :
: :
: :
:
:
: you are using the wrong function.
: fprintf(fp,"\nHai How are You ?\n");
:
: perror goes to stderr, not to a file. So you have to call freopen() as previously suggested.
: stream = freopen( "abc.tct", "w", stderr );
:
: see the example program here:
: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vccore98/HTML/_crt_freopen.2c_._wfreopen.asp
:
:
:
:
He mentioned that he didn't want to use fprintf. So I figured he knows that function and has some argument not to use it.



Greets,
Eric Goldstein
http://www.gvh-maatwerk.nl

: He mentioned that he didn't want to use fprintf. So I figured he knows that function and has some argument not to use it.
:

this seems to work

#include<stdio.h>
#include<stdlib.h>

int main()
{
    FILE* stream1 = freopen( "d:\\abc.txt", "w", stdout ); 
    FILE* stream2 = freopen( "d:\\abc.txt", "a+", stderr ); 
    printf("Hello there\n");
    perror(NULL);
    fclose(stream1);
    fclose(stream2);
     return 0;
}