index, rindex - string operations


     #include <strings.h>

     char *index(const char *s, int c);

     char *rindex(const char *s, int c);


     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.


     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.


     bstring(3C), malloc(3C), string(3C)

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