From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steve Graegert Subject: Re: Variable to sizeof function. Date: Sat, 16 Jul 2005 00:35:26 +0200 Message-ID: <6a00c8d505071515355f041394@mail.gmail.com> References: <20050715175352.93741.qmail@web31910.mail.mud.yahoo.com> Reply-To: Steve Graegert Mime-Version: 1.0 Content-Transfer-Encoding: 7BIT Return-path: In-Reply-To: <20050715175352.93741.qmail@web31910.mail.mud.yahoo.com> Content-Disposition: inline Sender: linux-c-programming-owner@vger.kernel.org List-Id: Content-Type: text/plain; charset="us-ascii" To: Vikas S Cc: Rechberger Markus , linux-c-programming@vger.kernel.org On 7/15/05, Vikas S wrote: > > I guess I was not clear. Say, we have two structures. > > str1 {int x, char y} and str2 {int x, char *y}; OK... > printf(sizeof(struct str1)); will give proper output. ie memory occupied > by str1. ...reasonable... > What I want is, instead of hard-coding str1 etc., I want to find > the size of structure which I will give as 1st argument. So, if the > program name is size, i'll give: > $ ./size str1 --- to get size of str1 > $ ./size str2 --- to get size of str2 This makes things even more confusing to me. So, you want (a) query the size of a particular structure among others (b) provide a structure as an argument to your program identified by name? Obviously (b) is something completely impossible, obscure at least. The solution to (a) is simple: struct s1 { int i; char *c; } str1; struct s2 { int i; char c[5]; } str2; if (argc != 2) return 0; if (!strcmp(argv[1], "str1")) printf("sizeof(str1): %d\n", sizeof(str1)); else printf("sizeof(str2): %d\n", sizeof(str2)) $ cc -o test test.c $ ./test str2 sizeof(str2): 12 > The code which I gave earlier is giving compile-time error message. > > Thanks, > Vikas > --- Rechberger Markus wrote: > > > strlen on a null pointer will segfault... > > if arc is 1 then argv[0] will contain a pointer to an array of char > > if arc is 2 then argv[1] (the users first argument) will contain an > > array of char.. > > so don't forget to check the number of arguments .. > > > > On 7/15/05, Vadiraj wrote: > > > Vikas, > > > > > > On 7/15/05, Vikas S wrote: > > > > I want to find out the size of a structure which the user will give as an argument > > > > as follows. > > > > > > > > #include <> -- All includes.. > > > > .. > > > > main(int arc, char *argv[]) > > > > > > argv is a charecter pointer . You cannot pass struct * as an > > > arguement to main. > > > > > > > { > > > > printf("Size of structure %s is: %d\n", argv[1], sizeof(struct argv[1])); > > > > > > use strlen(argv[1]) to find the lenght of the string. > > > > > > -- > > > cheers, > > > Vadi > > > - > > > To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in > > > the body of a message to majordomo@vger.kernel.org > > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > > > - > > To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > > > > > > __________________________________ > Do you Yahoo!? > Yahoo! Mail - You care about security. So do we. > http://promotions.yahoo.com/new_mail > - > To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- ______________________________________ Steve Graegert // Software Consultancy // Whether you know it or not, if you Mobile: +49 (176) 21248869 // are a hacker, you are a revolutionary. Office: +49 (9131) 7126409 // Don't worry, you're on the right side. ____________________________// -- Dr Crash / Phrack 6 / phile 3