Beginner help about strings

yildiz.a · 04-27-2009, 03:23 PM

Hi,

I created this code:

--------------------------------------------------
#include<string.h>

char a1[ ]="Available";

//and when a condition is provided, I want to change value of a1 to "N/A"
--------------------------------------------------

How can I do this? Thanks...

quzah · 04-27-2009, 03:32 PM

Use a pointer, and just assign it the constant "N/A". Or, use an array that actually has a size, and copy the elements that you need.

Quzah.

yildiz.a · 04-27-2009, 03:46 PM

Thanks...

c.user · 04-27-2009, 07:30 PM

you can use only

Code:

    char a1[ ]="Available";

if you are not use any functions from string.h like strcpy

MK27 · 04-27-2009, 07:43 PM

Quote:

Originally Posted by c.user

you can use only

Code:

    char a1[ ]="Available";

if you are not use any functions from string.h like strcpy

Even considering your english is not perfect (that is OK with me), this is NONSENSE. Not true.

You (c.user) should for your own good explain why you believe this. Look:

Code:

#include <stdio.h>
#include <string.h>

int main() {
	char a1[]="Available";
	strcpy(a1,"NONSENSE");
	printf("%s\n",a1);	
	return 0;
}

c.user · 04-27-2009, 09:05 PM

you may compile this, there are no errors

Code:

main()
{
    char a[] = "Available";
    return 0;
}

Code:

#include <stdio.h>

/* change value of array to another */
main()
{
    char a[] = "Available";
    const char *n = "N/A";
    unsigned len;

    sprintf(a, "%.*s", (len = sizeof a) > 0 ? len-1 : 0, n);
    printf("%s\n", a);
    return 0;
}

where is string.h ?

oh, the program doesn't need it

update:
'\0' will be added

quzah · 04-27-2009, 09:08 PM

Quote:

Originally Posted by c.user

where is string.h ?

oh, the program don't need it

Not all string functions are in the string header.

Quzah.

MK27 · 04-27-2009, 09:20 PM

Quote:

Originally Posted by c.user

you may compile this, there are no errors

This is a fine option so I won't hold you up to a firing squad, but it still does not make sense of what you said before, which was that "you can only use [this] if you are not using string.h".

c.user · 04-27-2009, 09:34 PM

MK27,

Quote:

Originally Posted by my

any functions from string.h

if he does not use any function from string.h, he does not need string.h in the program

string - is a chars + '\0'
string function - is a function for string which has '\0'

quzah · 04-28-2009, 02:37 PM

Quote:

Originally Posted by c.user

string function - is a function for string which has '\0'

Any time you use an incomplete array, and declare it with an assignment from a string in quotes, it automatically has room for the null character.

Because you've just used a string in quotes...

Therefore, assuming you don't run off the end of the array's size there, most string functions will work just fine.

Quzah.

strictlyC · 04-28-2009, 03:08 PM

Why not just create two char arrays?

Code:

char a1[] = "Available";
char a2[] = "NotAvailable";

And have your condition just call the one thats needed?
And if your worried about the space just have one

Code:

char a2[] = "NotAvailable";

If you need to print Available
just start printing the char array from

Code:

a2[3] until '\0'

If your just wanting to change the contents of the array that contains Available

Just do

Code:

if(condition)
{
a1[0] = 'N';
a1[1] = '/';
a1[3] = 'A';
a1[4] = '\0';
}

The rest of the array wont matter.
But you cant stuff more stuff into the array without deleteing what was already there unless you made the array large enough to hold both to start with.

quzah · 04-28-2009, 03:10 PM

Quote:

Originally Posted by strictlyC

Why not just create two char arrays?

Code:

char a1[] = "Available";
char a2[] = "NotAvailable";

And have your condition just call the one thats needed?

Or...

Code:

printf( "%sAvailable", available ? "" : "Not " );

Quzah.

c.user · 04-28-2009, 03:43 PM

Quote:

Originally Posted by quzah

Any time you use an incomplete array, and declare it with an assignment from a string in quotes, it automatically has room for the null character.

If array is complete

Code:

    char a[5] = "abcde";

there will no '\0' in it

and strcpy will continue copying while it will not get a '\0'

and

Code:

#include <string.h>
...
    char a_mess[] = "Available";
    
    strcpy(a_mess, a);

can cause segfault because a[5] may be a trash (not '\0')

(a[5] like a sixth element of array a)

quzah · 04-28-2009, 03:49 PM

Quote:

Originally Posted by c.user

If array is complete

It wasn't. That was the whole point.

Quote:

Originally Posted by c.user

and strcpy will continue copying while it will not get a '\0'

Which has nothing to do with the original post or the associated comment. No one was saying "Hey, if you use a malformed array as a string and try to use string functions over top of this array, it's not going to work!"

Quzah.

strickyc · 04-28-2009, 04:22 PM

Quote:

Originally Posted by c.user

If array is complete

Code:

    char a[5] = "abcde";

there will no '\0' in it

I dont think anyone said anything about initializing the array like that, not even the original poster.

04-27-2009, 03:23 PM	#1
yildiz.a Registered User Join Date: Apr 2009 Location: ISTANBUL Posts: 8	Beginner help about strings Hi, I created this code: -------------------------------------------------- #include<string.h> char a1[ ]="Available"; //and when a condition is provided, I want to change value of a1 to "N/A" -------------------------------------------------- How can I do this? Thanks...
yildiz.a is offline

04-27-2009, 03:32 PM	#2
quzah +++ OK NO CARRIER Join Date: Oct 2001 Posts: 10,262	Use a pointer, and just assign it the constant "N/A". Or, use an array that actually has a size, and copy the elements that you need. Quzah. __________________ Hundreds of thousands of dipshits can't be wrong. Are you up for the suck?
quzah is offline

04-27-2009, 03:46 PM	#3
yildiz.a Registered User Join Date: Apr 2009 Location: ISTANBUL Posts: 8	Thanks...
yildiz.a is offline

04-27-2009, 07:30 PM	#4
c.user Registered User Join Date: Apr 2009 Location: Russia Posts: 116	you can use only Code: char a1[ ]="Available"; if you are not use any functions from string.h like strcpy
c.user is offline

04-27-2009, 09:05 PM	#6
c.user Registered User Join Date: Apr 2009 Location: Russia Posts: 116	you may compile this, there are no errors Code: main() { char a[] = "Available"; return 0; } Code: #include <stdio.h> /* change value of array to another / main() { char a[] = "Available"; const char n = "N/A"; unsigned len; sprintf(a, "%.s", (len = sizeof a) > 0 ? len-1 : 0, n); printf("%s\n", a); return 0; } where is string.h ? oh, the program doesn't need it update: '\0' will be added Last edited by c.user; 04-27-2009 at 09:28 PM.*
c.user is offline

04-28-2009, 03:08 PM	#11
strictlyC Registered User Join Date: Apr 2009 Posts: 16	Why not just create two char arrays? Code: char a1[] = "Available"; char a2[] = "NotAvailable"; And have your condition just call the one thats needed? And if your worried about the space just have one Code: char a2[] = "NotAvailable"; If you need to print Available just start printing the char array from Code: a2[3] until '\0' If your just wanting to change the contents of the array that contains Available Just do Code: if(condition) { a1[0] = 'N'; a1[1] = '/'; a1[3] = 'A'; a1[4] = '\0'; } The rest of the array wont matter. But you cant stuff more stuff into the array without deleteing what was already there unless you made the array large enough to hold both to start with. Last edited by strictlyC; 04-28-2009 at 03:11 PM.
strictlyC is offline

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