Thread: make a function like printf/sprintf

Hi, I am writing a small function that logs a string passed to it to a log file. Right now
it looks like this:

Code:

int logData(char* logMessage);

int logData(char* logMessage) {
    FILE *pFile = NULL;   
    char logMsg[1024];    

      /* Create a new file we can write */
      pFile = fopen(DEBUGFILE, "a+");
      if ( pFile == NULL )
      {
          syslog(LOG_ERR,"Unable to open DEBUGFILE for reading");
          return 1; 
      }

      fprintf(pFile, %s\n", logMessage);
      fclose(pFile); /* Close the file */

      return 0;
}

But in order to have a line like this ("We are in %s on line %s", __FUNCTION__, __LINE__);
I have to do this:

Code:

    sprintf(logMsg, "We are in %s on line %s", __FUNCTION__, __LINE__);
    logData(logMsg);

I want to do this:

Code:

    logData("We are in %s on line %s", __FUNCTION__, __LINE__);

Sorry if this is basic, but I am still a beginner. Thanks!

Originally Posted by Dave_Sinkula

http://web.archive.org/web/200502070...t.html#4.9.6.7

hmm, I looked through but other than usage, I didn't see much, please let me know if I am mistaken. Also links are dead. Thanks.

can anyone tell me why this isn't working?

Code:

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

void myLogger(int log_level, char* logMessage, const char *format, ...)
{
    FILE *file = fopen("c:\file.txt", "a+");
    va_list args;
    time_t now;
    int debugValue = 1;
    
    if ( time(&now) != (time_t)(-1) )
    {
        struct tm *local = localtime(&now);
        if ( local )
        {
            char timestamp[20];
            if ( strftime(timestamp, sizeof timestamp, "%Y-%m-%d %X", local) )
            {
                fprintf(file, "%s : ", timestamp);
            }
        }
    }
    
    switch (log_level)
    {
        case 0:
            if ( 0 < debugValue )
            {
                fprintf(file, "%s, we got %d as debug_level ", debugValue, logMessage);
                va_start(args, format);
                vfprintf(file, format, args);
                va_end(args);
                fputc('\n', file);
                fclose(file);
            }
            break;

        default:
            if ( log_level <= debugValue )
            {
                fprintf(file, "%s, we got %d as debug_level ", debugValue, logMessage);
                va_start(args, format);
                vfprintf(file, format, args);
                va_end(args);
                fputc('\n', file);
                fclose(file);
            }
            break;
    }
}

int main(void)
{
   int i = 42;
   double d = 123.456;

   //myLogger(1, "This is a test: %d", debugValue);
   myLogger(1,"%s", "ok");
   myLogger(1,"i = %d, d = %g", i, d);
    
    return 0;
}

Got it to work like this:

Code:

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

void myLogger(int log_level, const char *format, ...)
{
    static const char filename[] = "c:\\test.txt";
    FILE *file = fopen(filename, "a+");
    va_list args;
    time_t now;
    int debugValue = 1;
    
    if ( time(&now) != (time_t)(-1) )
    {
        struct tm *local = localtime(&now);
        if ( local )
        {
            char timestamp[20];
            if ( strftime(timestamp, sizeof timestamp, "%Y-%m-%d %X", local) )
            {
                fprintf(file, "%s : ", timestamp);
            }
        }
    }
    
    switch (log_level)
    {
        case 0:
            if ( 0 < debugValue )
            {
                fprintf(file, "we got %d as debug_level", debugValue);
                va_start(args, format);
                vfprintf(file, format, args);
                va_end(args);
                fputc('\n', file);
                fclose(file);
            }
            break;

        default:
            if ( log_level <= debugValue )
            {
                fprintf(file, "we got %d as debug_level", debugValue);
                va_start(args, format);
                vfprintf(file, format, args);
                va_end(args);
                fputc('\n', file);
                fclose(file);
            }
            break;
    }
}

int main(void)
{
   int i = 42;
   double d = 123.456;

   myLogger(1,"i = %d, d = %g", i, d);
   return 0;
}

Originally Posted by vart

you still not checking return value of fopen

Right, I meant I got the function working.. I will add checks after.