Finding length of char array

Question

I have some code as follows   int i 0  char a 7   0x00 0xdc 0x01 0x04   int len 0  len   sizeof a   printf  The Length is    d   len     Here I want to find the length of the array a in c  How can this be done

User · Answer

You can try this      char tab 7    a   b   t   u   a   y   t       printf   d n  sizeof tab  sizeof tab 0

User · Answer

By convention C strings are  null-terminated   That means that there s an extra byte at the end with the value of zero  0x00   Any function that does something with a string  like printf  will consider a string to end when it finds null  This also means that if your string is not null terminated  it will keep going until it finds a null character  which can produce some interesting results   As the first item in your array is 0x00  it will be considered to be length zero  no characters    If you defined your string to be   char a 7   0xdc 0x01 0x04 0x00     e g  null-terminated  then you can use strlen to measure the length of the string stored in the array   sizeof measures the size of a type  It is not what you want  Also remember that the string in an array may be shorter than the size of the array

User · Answer

sizeof returns the size of the type of the variable in bytes  So in your case it s returning the size of your char 7  which is 7   sizeof char   Since sizeof char    1  the result is 7   Expanding this to another example   int intArr 5   printf  sizeof intArr   u   sizeof intArr      would yield 5   sizeof int   so you d get the result  20   At least on a regular 32bit platform  On others sizeof int  might differ   To return to your problem   It seems like  that what you want to know is the length of the string which is contained inside your array and not the total array size   By definition C-Strings have to be terminated with a trailing   0   0-Byte   So to get the appropriate length of the string contained within your array  you have to first terminate the string  so that you can tell when it s finished  Otherwise there would be now way to know   All standard functions build upon this definition  so if you call strlen to retrieve the str ing len gth  it will iterate through the given array until it finds the first 0-byte  which in your case would be the very first element   Another thing you might need to know that only because you don t fill the remaining elements of your char 7  with a value  they actually do contain random undefined values    Hope that helped

User · Answer

If anyone is looking for a quick fix for this  here s how you do it   while  array i       0   i      The variable i will hold the used length of the array  not the entire initialized array  I know it s a late post  but it may help someone

User · Answer

If you are expecting 4 as output then try this      char a    0x00 0xdc 0x01 0x04

User · Answer

You can do len   sizeof a  sizeof  a  for any kind of array  But  you have initialized it as a 7          meaning its length is 7

[c] Finding length of char array

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