Logging into a file

[FleshCrawler]

Any Idea how i can log into a file?
like that what gets written in the dosbox, i get logged into a file. like a program.log ot logfile.txt , i have no idea how to fix something like that.

tnx in advance

[WhytWulf]

here is the code I use for my log file writer..in might be of use to someone. functions like printf();

Code: Select all

#include <stdio.h>
#include <stdarg.h>
#include <time.h>

void InitLog(void)
{
	//creates logfile "sprawl.log" if it doesn't exist

	FILE *LogFile;

	time_t current = time(NULL);
	if((LogFile=fopen("Runner.log","w+"))!=NULL)
	{
		fprintf(LogFile,"Log File started %s",ctime(&current));
		fclose(LogFile);
	}

}

void LogWrite(char *string, ...)
{

	char LogString[1000];
	va_list ap;
	va_start(ap, string);
	vsprintf(LogString,string,ap);
	va_end(ap);
	FILE *filelog;
	time_t current = time(NULL);
	if ((filelog=fopen("Runner.log","a"))!=NULL)
	{
		fprintf(filelog,"-> %s: %s",ctime(&current),LogString);
		fprintf(filelog,"\n");
		fclose(filelog);
	}

}

To use call InitLog(); this deletes the file blah blah and creates a new file.
and when you want to output something to the logfile, use

Code: Select all

LogWrite("This is a test output variable %d\n",output);

It is quite versitile..It could easily be added to and made into a monster debug/log file..

[FleshCrawler]

thanks very much

[FleshCrawler]

Digging this old topic up again, but i felt like it was useless to create a complete new topic on the same subject

My Logwriter works fine so far, but i got the following problem, i want to let it write wich kind of renderer and Resolution the app. is running.

but when i use the LogWrite function like

LogWrite("Render: %d on Resolution: %d", DriverType, ResolutionType);

so if someone has a solution for that, thanks in advance

[Gonosz]

I am not quite sure what you are talking about :], but if you are saying you are looing for a printf-like function, then here it goes:

Code: Select all

inline void logwrite(char* logline, ...)
{
        va_list pfmt;
    FILE * fp = fopen("log.txt", "a");
    if (fp == NULL)
       return;
    if (logline != NULL)
        {
            va_start(pfmt, logline);
            vfprintf(fp, logline, pfmt);
            fprintf(fp,"\n");
            fclose(fp);
            va_end(pfmt);  
        }
}

BTW if you don't close the file and your app crashes, chances are that the logfile will be gone.

Hope I helped,

Gonosz

[FleshCrawler]

well, i got this:

Code: Select all

void InitLog(void) 
{ 
   //creates logfile "Astornia.log" if it doesn't exist 

   FILE *LogFile; 

   time_t current = time(NULL); 
   if((LogFile=fopen("Astornia.log","w+"))!=NULL) 
   { 
      fprintf(LogFile,"Log File started %s \n",ctime(&current)); 
      fclose(LogFile); 
   } 

} 

void LogWrite(char *logstr) 
{ 

   char LogString[1000]; 
   va_list ap; 
   va_start(ap, logstr); 
   vsprintf(LogString,logstr,ap); 
   va_end(ap); 
   FILE *filelog; 
   time_t current = time(NULL); 
   if ((filelog=fopen("Astornia.log","a"))!=NULL) 
   { 
      fprintf(filelog,"%s",LogString); 
      fclose(filelog); 
   } 

}

and i cant add more parameters to it, because i only wanna have it for 1 function. to show the driver, and resolution in the logfile

[Gonosz]

Okay. You can use vsprintf, which is like printf, but the output goes to a char[]. Then you can pass this string to your logwrite.

[FleshCrawler]

when i change it VC6 gives me the following error.

c:\program files\microsoft visual studio\myfiles\projects\astornia\logwriter.h(43) : error C2664: 'vsprintf' : cannot convert parameter 1 from 'struct _iobuf *' to 'char *'

i dont know so much about C/C++ yet. still learning

[Gonosz]

I don't think I can help without seeing you're source, so I copied a working function here for you (it's from the Half-Life SDK). BTW this is C, not C++

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void UTIL_LogPrintf( char *fmt, ... )
{
        va_list        argptr;
        char    string[1024];
        
        va_start ( argptr, fmt );
        vsprintf ( string, fmt, argptr );
        va_end   ( argptr );
        logwrite( string );  
}

EDIT:
Damn I am stupid, it is in the code you posted above You actually use the vsprintf in the logwrite! Anyway, this just proves that I didn't give you a bad advice Another idea: maybe you passed the file pointer as the first argument instead of the char[]... maybe

Okay, I'm off to learn reading

Gonosz<helpdesk>

[FleshCrawler]

Another idea: maybe you passed the file pointer as the first argument instead of the char[]... maybe

could you explain plz

and everyone can make reading mistakes, no big problem

[Gonosz]

Code: Select all

char string[200];
vsprintf ( string, "Render: %d on Resolution: %d\n", DriverType, ResolutionType);
LogWrite(string);

This should work.

[FleshCrawler]

it still says it cant take 4 parameters, vsprintf that is,

but if i remove em one by one, it says cant take 3 ,2 ,1...somehow i dont understand

but as you wrote it there, it actually has to work :S

[FleshCrawler]

I guess i will never get that fixed. been thinking how to solve, asked a friend, he didnt know the solution because he uses CBuilder. and only knew the CBuilder solution that doesnt work in VC6. so if someone is out there that does know the solution to this, i'm like begging to help me with a code to solve it, i'm really desperate...

[Halan]

okay this is an old topic i know but i used the code for logging

when compiling it says "`va_start' used in function with fixed args+"
any ideas?

greets,
Halan

[hybrid]

Learn C, read your compiler manual, try google. va_start is a function which is required for variable argument lists. This is plain ANSI C.