osx man page for tk_uid

Tk_GetUid(3)						       Tk Library Procedures						      Tk_GetUid(3)

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NAME
       Tk_GetUid, Tk_Uid - convert from string to unique identifier

SYNOPSIS
       #include <tk.h>

       Tk_Uid
       Tk_GetUid(string)

ARGUMENTS
       char *string (in)			 String for which the corresponding unique identifier is desired.
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DESCRIPTION
       Tk_GetUid  returns  the	unique identifier corresponding to string.  Unique identifiers are similar to atoms in Lisp, and are used in Tk to
       speed up comparisons and searches.  A unique identifier (type Tk_Uid) is a string pointer and may be used anywhere that a variable of  type
       "char  *"  could  be  used.   However, there is guaranteed to be exactly one unique identifier for any given string value.  If Tk_GetUid is
       called twice, once with string a and once with string b, and if a and b have the same string value (strcmp(a, b) == 0), then Tk_GetUid will
       return  exactly	the  same Tk_Uid value for each call (Tk_GetUid(a) == Tk_GetUid(b)).  This means that variables of type Tk_Uid may be com-
       pared directly (x == y) without having to call strcmp.  In addition, the return value from Tk_GetUid will have the same string value as its
       argument (strcmp(Tk_GetUid(a), a) == 0).

KEYWORDS
       atom, unique identifier

Tk																      Tk_GetUid(3)