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Full Discussion: compare null with non-null
Top Forums Shell Programming and Scripting compare null with non-null Post 302095005 by Corona688 on Thursday 2nd of November 2006 02:13:01 PM
Old 11-02-2006
Quote:
Originally Posted by nitin
Lets compare the first field, it is null. Well it has "" that but for database standpoint it is null. I guess I could strip that using vi and really make it a null.
Thinking on this, but, how would you tell the difference between a NULL and an empty string?
 

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index(3C)						   Standard C Library Functions 						 index(3C)

NAME
index, rindex - string operations SYNOPSIS
#include <strings.h> char *index(const char *s, int c); char *rindex(const char *s, int c); DESCRIPTION
The index() and rindex() functions operate on null-terminated strings. The index() function returns a pointer to the first occurrence of character c in string s. The rindex() function returns a pointer to the last occurrence of character c in string s. Both index() and rindex() return a null pointer if c does not occur in the string. The null character terminating a string is considered to be part of the string. USAGE
On most modern computer systems, you can not use a null pointer to indicate a null string. A null pointer is an error and results in an abort of the program. If you wish to indicate a null string, you must use a pointer that points to an explicit null string. On some machines and with some implementations of the C programming language, a null pointer, if dereferenced, would yield a null string. Though often used, this practice is not always portable. Programmers using a null pointer to represent an empty string should be aware of this portability issue. Even on machines where dereferencing a null pointer does not cause an abort of the program, it does not necessarily yield a null string. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ |ATTRIBUTE TYPE |ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ SEE ALSO
bstring(3C), malloc(3C), string(3C), attributes(5), standards(5) SunOS 5.11 24 Jul 2002 index(3C)
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