example 01: printing basic datatypes

#include <stdio.h>   // for printf

int main(int argc, char *argv[])
{
   // print "the date is: 05.01.2006",
   // i.e. 2- or 4-digit with leading zeros
   // using 32-bit 'long' datatype
   long lday   = 5;
   long lmonth = 1;
   long lyear  = 2006;
   printf("the date is: %02ld.%02ld.%04ld\n",lday,lmonth,lyear);

   // - print 8-digit hex value
   // - print a pointer value
   unsigned long ulID = 0x12345678;
   unsigned long *pID = &ulID;
   printf("hex value: 0x%02lX at address: %p\n", ulID, pID);

   // - print 4 bytes of a 32-bit ulong value
   //   as separate hex values
   unsigned char uc1 = (unsigned char)(ulID >> 24);
   unsigned char uc2 = (unsigned char)(ulID >> 16);
   unsigned char uc3 = (unsigned char)(ulID >>  8);
   unsigned char uc4 = (unsigned char)(ulID >>  0);
   printf("hex bytes: %02X %02X %02X %02X\n",uc1,uc2,uc3,uc4);

   // - print double value like "70.35000"
   double dTemp = 70.35;
   printf("temperature: %5.5f\n", dTemp);
}

output:

the date is: 05.01.2006
hex value: 0x12345678 at address: 0012FEDC
hex bytes: 12 34 56 78
temperature: 70.35000

#include <stdio.h>   // for printf
#include <string.h>  // for strchr

int main(int argc, char *argv[])
{
   // - print three strings,
   //   - the first  one with 10 chars, left-justified,
   //     and if there are more than 10 chars, truncate the rest.
   //   - the second one with 10 chars, right, prefixed with blanks
   //   - the third  one with  8 chars, right, prefixed with zeros
   char *psz1 = "FooBar Inc. formerly known as Foo Bar Systems Corp.";
   char *psz2 = "NY";
   char *psz3 = "105000";
   printf("company: %-10.10s | "    // continue on next line,
          "location: %10.10s | "    // strings are joined by compiler.
          "turnover: %08s$\n",
          psz1,psz2,psz3
         );

   // - find phrases in a string surrounded by < >
   // - print only the parts between < >
   char *pszFull = "This is a <highlight>hello "
                   "world</highlight> example.\n";
   for (char *pszCur=pszFull; *pszCur;)   // cursor
   {
      char *pszBra = strchr(pszCur, '<');
      if (!pszBra) break;
      pszBra++;   // skip '<'

      char *pszKet = strchr(pszBra, '>');
      if (!pszKet) break;

      // print n characters of a string, suppling length as int
      printf("phrase found: %.*s\n", (int)(pszKet-pszBra), pszBra);

      pszCur = pszKet;  // continue past phrase
   }
}

output:

company: FooBar Inc | location:         NY | turnover: 00105000$
phrase found: highlight
phrase found: /highlight

• writing an own printf-like function for error output
• printing a progress indicator

#include <stdio.h>   // for printf
#include <string.h>  // for strchr
#include <stdarg.h>  // for va_arg

#ifdef _WIN32
   #define vsnprintf _vsnprintf
#endif

int main(int argc, char *argv[])
{
   // create and use an own printf-like function "perr",
   // which behaves exactly like printf, but
   // -  prefixes the output with "error: "
   // -  prints to stderr stream, not stdout
   void  perr(const char *pszFormat, ...);   // see perr below
   char *pszFileName = "thetestfile.txt";
   long  lStatusCode = 100;
   perr("cannot open file: %s [rc %ld]\n", pszFileName, lStatusCode);

   // print a progress indicator:
   //    "processing file 000 of 050 (00%) ..."
   //    "processing file 001 of 050 (02%) ..."
   //    "processing file 002 of 050 (04%) ..."
   //    ...
   //    "processing file 049 of 050 (98%) ..."
   // but always within the same line.
   long iMaxFiles=50;
   for (long iFile=0; iFile<iMaxFiles; iFile++)
   {
      printf("processing file %03ld of %03ld "
             "(%02ld%%) ... \r",
             iFile, iMaxFiles, iFile*100/iMaxFiles
            );
      fflush(stdout);
   }
   printf("\nprocessing done.\n");

   return 0;
}

void perr(const char *pszFormat, ...)
{
   static char szErrBuf[200];
   va_list argList;
   va_start(argList, pszFormat);
   ::vsnprintf(szErrBuf, sizeof(szErrBuf)-10, pszFormat, argList);
   szErrBuf[sizeof(szErrBuf)-10] = '\0';
   fprintf(stderr, "error: %s", szErrBuf);
}

output: (after program completion)

error: cannot open file: thetestfile.txt [rc 100]
processing file 049 of 050 (98%) ...
processing done.