Question

C program to convert epoch date

Asked by: foxhelp

I have taken an example of a c program that you previously had for another incident which will take an epoch date such as 1229521513 and covnert it to Wed, Dec. 17 2008 13:45:13.  That is working good if I insert the 1229521513 in the c program.  What I want to do is call this C program from a cobol program and feed it the 1229521513 date and get an output of a date readable to a human such as Dec 17, 2008 13:45:13.  Below is the C code I used.

#include <time.h>
#include <stdio.h>
#include <string.h>
 
void main(void)
{
     struct tm *newtime;
     char am_pm[] = "AM";
     time_t long_time=1229521513;
 
     newtime = localtime(&long_time);
     if(newtime->tm_hour>12)
          strcpy(am_pm,"PM");
     if(newtime->tm_hour>12)
          newtime->tm_hour-=12;
     if(newtime->tm_hour ==0)
          newtime->tm_hour=12;
 
     printf("%.19s %s, %i\n", asctime(newtime),am_pm,
    1900+newtime->tm_year);
}
~
~
"UNIXD.c" 22 lines, 475 characters

                                  
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Asked On
2008-12-23 at 13:26:55ID24006824
Topics

COBOL Programming Language

,

C Programming Language

Participating Experts
3
Points
500
Comments
11

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Answers

 

by: Infinity08Posted on 2008-12-24 at 03:51:29ID: 23239652

Try the below code. You pass the epoch as a command line argument, for example :

        UNIXD 1229521513

#include <stdio.h>
#include <time.h>
 
int main(int argc, char *argv[]) {
  unsigned long epoch = 0;
  time_t tt = 0;
  char timestamp[64] = "";
 
  if ((argc < 2) || (!sscanf(argv[1], "%lu", &epoch))) {
    return 1;
  }
  
  tt = epoch;
  strftime(timestamp, 64, "%c", localtime(&tt));
  /*strftime(timestamp, 64, "%a, %b. %d %Y %X", localtime(&tt));*/  /* <--- or this */
 
  puts(timestamp);
 
  return 0;
}

                                              
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by: foxhelpPosted on 2008-12-24 at 09:43:35ID: 23241147

Thanks for the response.  I am going to call this c routine from a cobol program with a statement such as the following:  call "UNIXD" using date-field and date-field is going to contain the 1229521413 number.  What field in the C program accepts that date?  And, to get the output back into my cobol program, what field do I accept?
Thanks for the quick response and happy holidays!

 

by: earthman2Posted on 2008-12-26 at 03:00:45ID: 23244795

the program will put its timestamp string to STDOUT.  So you could pipe that to a file then read the file.

call "UNIXD 1229521413 > tstamp.dat"

 

by: Infinity08Posted on 2008-12-26 at 04:30:27ID: 23244925

>> What field in the C program accepts that date? And, to get the output back into my cobol program, what field do I accept?

As I said, you pass it as an argument when calling the UNIXD program :

        UNIXD 1229521513

Try compiling the C program, and call it from a command line using the above, and you'll see that the result is the timestamp in string format written out to standard output (as correctly said by earthman2)


I have never worked with Cobol, so I don't know how you will call the C program, and what options you have for retrieving the result. If you can elaborate a bit on what possibilities there are, we can check whether the above program will meet the requirements, or whether it needs to be modified in some way.

 

by: earthman2Posted on 2008-12-28 at 14:43:37ID: 23253180

I would have thought you can mix languages with your operating system.  This entails writing a wrapper for your c function that can be called from COBOL,  this would be a lot more efficient than spawning a separate process.

 

by: woolmilkporcPosted on 2008-12-28 at 15:06:13ID: 23253247

Hi again,

I think you should have a look at this document ('Example: COBOL program calling C/C++ functions')

http://publib.boulder.ibm.com/infocenter/comphelp/v7v91/index.jsp?topic=/com.ibm.aix.cbl.doc/tpsubw20.htm

Perhaps it will help a bit.

Good luck!

wmp

 

by: foxhelpPosted on 2009-01-08 at 13:54:10ID: 23330657

Hello, the above program works and I figured out how to call it from Cobol but I get an error on "main".  Is there anything else I can use instead of int main(int argc, char *argv[]) {
I get the following error when I compile it:
cob: entry defined: MARNEW, conflicting "main" found in: UNIXDD.o

 

by: Infinity08Posted on 2009-01-08 at 14:15:40ID: 23330837

If you linked to the compiled object file, then you can simply name the function whatever you like instead of 'main'. The 'main' was needed for a stand-alone C program.

 

by: foxhelpPosted on 2009-01-08 at 15:51:31ID: 23331487

Thank you so much for that response.  That worked and I was able to link the program into my cobol program and run it without errors.  The only problem I have now is that if I put in an epoch date of 1229521513, it comes back with Wed Dec 31 19:00:00 1969.  The translation should be as follows: 1229521513 translates to Wednesday, December 17th 2008, 18:45:13 (GMT +5).  Is there something wrong with the formula?

 

by: Infinity08Posted on 2009-01-09 at 00:21:09ID: 23333612

>> Is there something wrong with the formula?

There's likely something wrong with the way you call the function, since it seems the C code got the value 0, rather than 1229521513. 0 corresponds to :

        Thu Jan 1 00:00:00 1970 (GMT)               <--- UTC time
        Wed Dec 31 19:00:00 1969 (GMT - 5)      <--- local time

If you can easily call the function with a string ('\0'-terminated array of characters) as argument, then you could use code a bit like below. Note that it's not thread safe due to the static.

You call the function by passing it a string, and getting a string in return. Called in C, it would look like this :

        const char *ts = getTimestamp("1229521513");

For Cobol I don't know ;)

/*#include <stdio.h>*/ /* <--- for debug purposes */
#include <time.h>
 
const char *getTimestamp(const char *epochStr) {
  static char timestamp[64] = "";
  unsigned long epoch = 0;
  time_t tt = 0;
 
  memset(timestamp, '\0', 64);
  if (epochStr && sscanf(epochStr, "%lu", &epoch)) {
    /*fprintf(stderr, "Got epoch : %lu\n", epoch);*/ /* <--- for debug purposes */
    tt = epoch;
    strftime(timestamp, 64, "%c", localtime(&tt));
    /*strftime(timestamp, 64, "%a, %b. %d %Y %X", localtime(&tt));*/  /* <--- or this */
  }
 
  /*fprintf(stderr, "Got timestamp : %s\n", timestamp);*/ /* <--- for debug purposes */
 
  return timestamp;
}

                                              
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