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confuse about strlen

 
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chongado



Joined: 25 Apr 2009
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confuse about strlen
PostPosted: Sun Apr 26, 2009 9:39 pm     Reply with quote

Hi there, I'm confusing about function strlen()

when I coding like this

char str[10];

str[0]='a';

when I show the result of strlen(str), It'll be 3.

why??? why it didn't be 1?

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asmallri



Joined: 12 Aug 2004
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PostPosted: Sun Apr 26, 2009 9:53 pm     Reply with quote

You did not use any string functions to populate your string. If you want to do it manually then you need to terminate the string with a 0x00.

Code:
char str[10];

str[0]='a';
str[1]=0x00;


This will give you a string length of 1.
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chongado



Joined: 25 Apr 2009
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about terminate character
PostPosted: Sun Apr 26, 2009 10:25 pm     Reply with quote

Thank you.
Wayne_



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PostPosted: Mon Apr 27, 2009 2:07 am     Reply with quote

char str[10]; defines a char array which can hold upto 10 characters.

A string is series of chars terminated with a 0 NOT the char '0' but the value 0 which is the same as the char '\0' or null

Your code defines a char array and then sets the first value to 'a' the rest is random data and it just so happens that when you ran your code str[3] == '\0' which meant that strlen(str) returns the value 3.

As you have defined your char array as [10] you can only store a tring of upto 9 values for your string as the last char must contain the terminator '\0' or 0
chongado



Joined: 25 Apr 2009
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PostPosted: Mon Apr 27, 2009 3:08 am     Reply with quote

Wayne_ wrote:
char str[10]; defines a char array which can hold upto 10 characters.

A string is series of chars terminated with a 0 NOT the char '0' but the value 0 which is the same as the char '\0' or null

Your code defines a char array and then sets the first value to 'a' the rest is random data and it just so happens that when you ran your code str[3] == '\0' which meant that strlen(str) returns the value 3.

As you have defined your char array as [10] you can only store a tring of upto 9 values for your string as the last char must contain the terminator '\0' or 0


Thank you

You mean I should use the last of array to '/0'
can I code this " str[1]='/0' ", right?
Wayne_



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PostPosted: Mon Apr 27, 2009 4:48 am     Reply with quote

Make sure you use the correct \

If you only want the one char in your string then you need to do
Code:
str[0] = 'a';
str[1] = '\0';

or you could do
Code:
strcpy(str, "a");

which may be better because if you change the number of chars the first
way becomes complicated and is prone to errors.
Code:

str[0] = 'h';
str[1] = 'e';
str[2] = 'l';
str[3] = 'l';
str[4] = 'o';
str[5] = '\0';

same as
Code:
strcpy(str, "hello");
chongado



Joined: 25 Apr 2009
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Thank you
PostPosted: Mon Apr 27, 2009 11:54 pm     Reply with quote

Hi There thank you so much I can do it ^^

'\0' lovely character
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