source: vendor/bash/3.1-p17/examples/loadables/printenv.c

/*
 * printenv -- minimal builtin clone of BSD printenv(1).
 *
 * usage: printenv [varname]
 *
 */

#include <config.h>
#include <stdio.h>

#include "builtins.h"
#include "shell.h"
#include "bashgetopt.h"

extern char **export_env;

int
printenv_builtin (list) 
     WORD_LIST *list;
{
  register char **envp;
  int opt;
  SHELL_VAR *var;

  reset_internal_getopt ();
  while ((opt = internal_getopt (list, "")) != -1)
    {
      switch (opt)
        {
        default:
          builtin_usage ();
          return (EX_USAGE);
        }
    }
  list = loptend;

  /* printenv */
  if (list == 0)
    {
      maybe_make_export_env ();         /* this allows minimal code */
      for (envp = export_env; *envp; envp++)
        printf ("%s\n", *envp);
      return (EXECUTION_SUCCESS);
    }

  /* printenv varname */
  var = find_variable (list->word->word);
  if (var == 0 || (exported_p (var) == 0))
    return (EXECUTION_FAILURE);

  if (function_p (var))
    print_var_function (var);
  else
    print_var_value (var, 0);

  return (EXECUTION_SUCCESS);
}

char *printenv_doc[] = {
        "print values of environment variables",
        (char *)NULL
};

struct builtin printenv_struct = {
        "printenv",
        printenv_builtin,
        BUILTIN_ENABLED,
        printenv_doc,
        "printenv [varname]",
        0
};