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7.10.5 Config file only example

If for some reason it is difficult or unworkable to integrate configuration file processing with command line option parsing, the libopts (see section libopts External Procedures) library can still be used to process configuration files. Below is a Hello, World! greeting program that tries to load a configuration file ‘hello.conf’ to see if it should use an alternate greeting or to personalize the salutation.

 
#include <config.h>
#include <sys/types.h>
#include <stdio.h>
#include <pwd.h>
#include <string.h>
#ifdef   HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <autoopts/options.h>
int main(int argc, char ** argv) {
  char const * greeting = "Hello";
  char const * greeted  = "World";
  tOptionValue const * pOV = configFileLoad("hello.conf");

  if (pOV != NULL) {
    const tOptionValue* pGetV = optionGetValue(pOV, "greeting");

    if (  (pGetV != NULL)
       && (pGetV->valType == OPARG_TYPE_STRING))
      greeting = strdup(pGetV->v.strVal);

    pGetV = optionGetValue(pOV, "personalize");
    if (pGetV != NULL) {
      struct passwd * pwe = getpwuid(getuid());
      if (pwe != NULL)
        greeted = strdup(pwe->pw_gecos);
    }

    optionUnloadNested(pOV); /* deallocate config data */
  }
  printf("%s, %s!\n", greeting, greeted);
  return 0;
}

With that text in a file named “hello.c”, this short script:

 
cc -o hello hello.c `autoopts-config cflags ldflags`
./hello
echo 'greeting Buzz off' > hello.conf
./hello
echo personalize > hello.conf
./hello

will produce the following output:

 
Hello, World!
Buzz off, World!
Hello, Bruce Korb,,,!

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