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hadeelqasaimeh
Joined: 05 Jan 2006 Posts: 105
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content of a specific location in a string |
Posted: Sat Jun 17, 2006 2:29 am |
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hi all
i need to know a content of a specific location in some string i have recieved from rs-232 port.
for example i need to know whats in S[10] in location 10,,so how to do?
thanx |
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Ttelmah Guest
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Posted: Sat Jun 17, 2006 3:09 am |
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In C, there is a 'cross correlation', between what are called 'pointers', and 'arrays'. If (for instance), you have:
char str[20];
//and then call:
gets(str);
//which sends the 'pointer' to 'str', to the function, then after the data is retrieved:
str[0] will contain the first character received.
So, 'strings', are just arrays of characters (with a '0' in the last location used), and can be accessed either way at will. Using the 'pointer' notation:
*(str+10)
will be the 'contents' of the _eleventh_ character in the string. Remember that throughout C, things arrays, pointers etc., are 'zero referenced', so a ten element string (str[10]), has elements str[0] to str[9]. Also that for a string, there must be a terminating '0', so only nine useable characters can actually be held in such a ten element array.
Forgetting that you need this 'extra' character, and the use of the zero location, are the two commonest problems with strings in C.
Best Wishes |
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garage Guest
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Posted: Sat Jun 17, 2006 11:41 pm |
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please if you have a simple example code of this!!
thank you |
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hadeelqasaimeh
Joined: 05 Jan 2006 Posts: 105
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Posted: Sat Jun 17, 2006 11:42 pm |
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thanx |
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Mark
Joined: 07 Sep 2003 Posts: 2838 Location: Atlanta, GA
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Re: content of a specific location in a string |
Posted: Sun Jun 18, 2006 9:00 pm |
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hadeelqasaimeh wrote: | hi all
i need to know a content of a specific location in some string i have recieved from rs-232 port.
for example i need to know whats in S[10] in location 10,,so how to do?
thanx |
The 10th character in a string is s[9]. |
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hadeelqasaimeh
Joined: 05 Jan 2006 Posts: 105
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so.... |
Posted: Mon Jun 19, 2006 12:08 am |
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hi
i understand that
Quote: | so a ten element string (str[10]), has elements str[0] to str[9]. |
from first reply
now mark said Quote: | The 10th character in a string is s[9].
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i think this different!!!!so what to do guyes?
if there is some example |
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asmallri
Joined: 12 Aug 2004 Posts: 1634 Location: Perth, Australia
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Posted: Mon Jun 19, 2006 12:31 am |
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assuming the following:
Code: |
char Mesg[20];
sprintf(Mesg, "Hello, world");
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the line
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printf("%c", Mesg[5])
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will print the , character
the line
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printf("%s", &Mesg[3]);
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will print the message
lo, world
Corrected - thanks Mark for spotting that deliberate error to test who was awake :-) _________________ Regards, Andrew
http://www.brushelectronics.com/software
Home of Ethernet, SD card and Encrypted Serial Bootloaders for PICs!!
Last edited by asmallri on Mon Jun 19, 2006 6:43 pm; edited 1 time in total |
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Mark
Joined: 07 Sep 2003 Posts: 2838 Location: Atlanta, GA
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Posted: Mon Jun 19, 2006 7:53 am |
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asmallri wrote: | assuming the following:
Code: |
char Mesg[20];
sprintf(Mesg, "Hello, world");
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the line
Code: |
printf("%c", *Mesg[5])
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will print the , character
the line
Code: |
printf("%s", &Mesg[3]);
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will print the message
lo, world |
I think you meant to write
Code: |
printf("%c", Mesg[5])
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