strvars - expand variables in string

       Lars Wirzenius (lars.wirzenius@helsinki.fi)

Publib                                        C Programmer's Manual                                STRVARS(3pub)

strvars  will  replaces  references  to  variables in the string str with the values of the variables.  A
       reference to a variable is of the form $(foo) or $x (where x is a single character, but not $).  A dollar
       sign is expressed in the string as $$, and will be converted to $ in the output.  Memory for the expanded
       string is allocated dynamically, and *res is set to point to it.

       The values of the variables are fetched using the function expand.  It is given the name of the  variable
       as its argument, and must return a pointer to the value, or NULL if that variable doesn't exist.

       To replace references to environment variables, one would the following.

            #include <publib.h>
            #include <stdlib.h>

            char line[1024];
            char *res;

            if (strvars(&res, line, getenv) == NULL)
                errormsg(1, 0, "strvars failed");
            printf("res = <%s>\n", res);

       strvars - expand variables in string

strvars  will  return  0  if successful, or NULL if an error occurred (malformed input string, result too
       big, or unknown variable).

publib(3), getenv(3)

       #include <publib.h>
       int strvars(char **res, const char *str, char *(*expand)(const char *));