NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/lang/c-part1/6187

Text File | 1996-08-05 | 3.3 KB | 105 lines

Path: mail2news.demon.co.uk!genesis.demon.co.uk
From: Lawrence Kirby <[e-mail]>
Newsgroups: comp.lang.c
Subject: Re: I can't print the date in the format I want.
Date: Fri, 23 Feb 96 00:35:32 GMT
Organization: none
Message-ID: <[e-mail]>
References: <4g5nbf$[e-mail]> <[e-mail]>
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In article <[e-mail]>
           [e-mail] "Robert B. Clark" writes:

>On 17 Feb 1996 18:11:43 -0500, [e-mail] (ASCII zero) wrote:
>
>>I am trying to use strftime() to format the date into YY-MM-DD. The format
>>seems to be working but I am unable to actually print the formatted
>>string. It compiles just fine using gcc. What have I overlooked?
>
>You need to check your compiler and make sure that you've not disabled
>those oh-so-useful warning messages:
>
>>main()
>
>NC.
>
>On second thought, I'll comment anyway.  Your function ought to return
>some sort of value, if for no other reason than to reduce the flamewars
>people tend to get into over various permutations of the main()
>declaration:
>
>        int main(void)

Good advice but be aware that if the return type of a function
is unspecified it defaults to int. so ``main() {}'' defines a function that
takes no arguments and returns int.

>> debug = strftime(str, 50, "The current date is %y-%m-%d", ptr);
>
>"Possible use of 'str' before definition."

Definite misuse of terminology :-)

str was defined on a previous line by char *str; . However this code certainly
reads the value of str before setting it i.e. it passes an undefined value
to strftime().

...

>> getchar();                           /* OK up to this point? */
>
>"Code has no effect."
>
>Doesn't do anything but wait for the user to press a key.  If that was
>your intent, it would be better to express this as
>
>        if getchar();

Perhaps you meant:

          if (getchar());

However all the if statement seems to do is obfuscate the code.

...

>Here is a slight revision of your code, with the disastrous null pointer
>taken care of by explicitly declaring a char array for str instead of
>just a char pointer:
>
>#include <stdio.h>
>#include <time.h>
>#include <string.h>             /* For strlen() function */
>#define SLEN            50      /* Allocate 50 chars for str */
>
>int main(void)
>{
>   struct tm *ptr;
>   time_t lt;
>   char str[SLEN];      /* Explicitly allocate 50 chars for str */
>   int debug;
>
>   lt = time(NULL);
>   ptr = localtime(<);
>   printf("\nThe system clock shows: %s\n\n",asctime(ptr));
>   debug=strftime(str,SLEN,"The current date is %y-%m-%d",ptr);
>   printf("\nThe value of 'debug' is %d"
>              "\nThe length of 'str' is %d", debug,strlen(str));
>   printf("\nFormatted time string: \"%s\"",str);
>   return debug;
>}

The only portable values to return from main() are 0, EXIT_SUCCESS and
EXIT_FAILURE (the last 2 being defined in stdlib.h). return 0 or return
EXIT_SUCCESS is probably sensible here.

--
-----------------------------------------
Lawrence Kirby | [e-mail]
Wilts, England | [e-mail]
-----------------------------------------