Array of char should end at 0 or 0

Question

Lets say we have an array of char pointers  char  array        abc    def       Now what should be put in the end    char  array        abc    def     0       or  char  array        abc    def     0       Though  both works  We only have to put the condition to check the end accordingly  like  array  index        0     or  array  index        0     My question is which one is the better way  Which is used by most programmers   Edit  Most answers say that NULL is better than   0  and   0   But I always thought that   NULL is same as   0  which is same as 0x0 or 0  Is it wrong

User · Accepted Answer

I would end it with NULL  Why  Because you can t do either of these   array index       0  array index       0    The first one is comparing a char   to a char  which is not what you want  You would have to do this   array index  0       0    The second one doesn t even work  You re comparing a char   to a char    yes  but this comparison is meaningless  It passes if the two pointers point to the same piece of memory  You can t use    to compare two strings  you have to use the strcmp   function  because C has no built-in support for strings outside of a few  and I mean few  syntactic niceties  Whereas the following   array index     NULL   Works just fine and conveys your point

User · Answer

Well  technically   0  is a character while   0  is a string  so if you re checking for the null termination character the former is correct  However  as Chris Lutz points out in his answer  your comparison won t work in it s current form

User · Answer

According to the C99 spec    NULL expands to a null pointer constant  which is not required to be  but typically is of type void     0  is a character constant  character constants are of type int  so it s equivalen to plain 0   0  is a null-terminated string literal and equivalent to the compound literal  char  2    0  0     NULL    0  and 0 are all null pointer constants  so they ll all yield null pointers on conversion  whereas   0  yields a non-null char    which should be treated as const as modification is undefined   as this pointer may be different for each occurence of the literal  it can t be used as sentinel value   Although you may use any integer constant expression of value 0 as a null pointer constant  eg   0  or sizeof foo - sizeof foo    int 0 0   you should use NULL to make your intentions clear

User · Answer

Of these two  the first one is a type mistake    0  is a character  not a pointer  The compiler still accepts it because it can convert it to a pointer   The second one  works  only by coincidence    0  is a string literal of two characters  If those occur in multiple places in the source file  the compiler may  but need not  make them identical   So the proper way to write the first one is  char  array        abc    def   NULL      and you test for array index   NULL  The proper way to test for the second one is array index  0     0   you may also drop the   0  in the string  i e  spell it as     since that will already include a null byte

User · Answer

Null termination is a bad design pattern best left in the history books   There s still plenty of inertia behind c-strings  so it can t be avoided there   But there s no reason to use it in the OP s example   Don t use any terminator  and use sizeof array    sizeof array 0   to get the number of elements

User · Answer

The termination of an array of characters with a null character is just a convention that is specifically for strings in C  You are dealing with something completely different -- an array of character pointers -- so it really has no relation to the convention for C strings  Sure  you could choose to terminate it with a null pointer  that perhaps could be your convention for arrays of pointers  There are other ways to do it  You can t ask people how it  should  work  because you re assuming some convention that isn t there

[c] Array of char* should end at '\0' or "\0"?

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