Node:Example programs, Next:A note from the original author, Previous:Debugging, Up:Top
The aim of this section is to provide a substantial example of C
programming, using input from and output to disk, GNU-style long
options, and the linked list data structure (including insertion,
deletion, and sorting of nodes).
#include <stdio.h>
#include <string.h>
#include <argp.h>
#define NAME_LEN 100
#define ADDR_LEN 500
const char *argp_program_version =
"bigex 1.0";
const char *argp_program_bug_address =
"<bug-gnu-utilsgnu.org>";
/* This structure is used by main to communicate with parse_opt. */
struct arguments
{
char *args[1]; /* No arguments to this function */
int verbose; /* The -v flag */
char *infile; /* Argument for -i */
char *outfile; /* Argument for -o */
};
struct personal_data
{
char name[NAME_LEN];
char address[ADDR_LEN];
struct personal_data *next;
};
/*
OPTIONS. Field 1 in ARGP.
Order of fields: {NAME, KEY, ARG, FLAGS, DOC}.
*/
static struct argp_option options[] =
{
{"verbose", 'v', 0, 0, "Produce verbose output"},
{"input", 'i', "INFILE", 0,
"Read addresses from INFILE"},
{"output", 'o', "OUTFILE", 0,
"Output to OUTFILE instead of to standard output"},
{0}
};
/*
PARSER. Field 2 in ARGP.
Order of parameters: KEY, ARG, STATE.
*/
static error_t
parse_opt (int key, char *arg, struct argp_state *state)
{
struct arguments *arguments = state->input;
switch (key)
{
case 'v':
arguments->verbose = 1;
break;
case 'i':
arguments->infile = arg;
break;
case 'o':
arguments->outfile = arg;
break;
case ARGP_KEY_ARG:
if (state->arg_num >= 1)
{
argp_usage(state);
}
arguments->args[state->arg_num] = arg;
break;
case ARGP_KEY_END:
if (state->arg_num < 1)
{
argp_usage (state);
}
break;
default:
return ARGP_ERR_UNKNOWN;
}
return 0;
}
/*
ARGS_DOC. Field 3 in ARGP.
A description of the non-option command-line arguments
that we accept.
*/
static char args_doc[] = "ARG";
/*
DOC. Field 4 in ARGP.
Program documentation.
*/
static char doc[] =
"bigex -- Add ARG new names to an address book file.\vThe largest code example in the GNU C Tutorial.";
/*
The ARGP structure itself.
*/
static struct argp argp = {options, parse_opt, args_doc, doc};
struct personal_data *
new_empty_node()
{
struct personal_data *new_node;
new_node = (struct personal_data*)
malloc (sizeof (struct personal_data));
strcpy (new_node->name, "");
strcpy (new_node->address, "");
new_node->next = NULL;
return new_node;
}
struct personal_data *
create_node()
{
int bytes_read;
int nbytes;
struct personal_data *current_node;
char *name;
char *address;
current_node = new_empty_node();
puts ("Name?");
nbytes = NAME_LEN;
name = (char *) malloc (nbytes + 1);
bytes_read = getline (&name, &nbytes, stdin);
if (bytes_read == -1)
{
puts ("ERROR!");
}
else
{
strncpy (current_node->name, name, NAME_LEN);
free (name);
}
puts ("Address?");
nbytes = ADDR_LEN;
address = (char *) malloc (nbytes + 1);
bytes_read = getline (&address, &nbytes, stdin);
if (bytes_read == -1)
{
puts ("ERROR!");
}
else
{
strncpy (current_node->address, address, ADDR_LEN);
free (address);
}
printf("\n");
return current_node;
}
struct personal_data *
find_end_node (struct personal_data *current_node)
{
if (current_node->next == NULL)
{
return current_node;
}
else
{
return find_end_node (current_node->next);
}
}
int
list_length (struct personal_data *root)
{
struct personal_data *current_node;
int count = 0;
current_node = root;
while (current_node->next != NULL)
{
current_node = current_node->next;
count++;
}
return count;
}
struct personal_data *
find_node (struct personal_data *root,
int node_wanted)
{
struct personal_data *current_node;
int index = 0;
current_node = root;
while ((index < node_wanted) && (current_node->next != NULL))
{
current_node = current_node->next;
index++;
}
return current_node;
}
delete_node (struct personal_data *root,
int location)
{
struct personal_data *previous_node;
struct personal_data *current_node;
previous_node = find_node (root, location - 1);
current_node = find_node (root, location);
previous_node->next = current_node->next;
}
insert_node (struct personal_data *root,
struct personal_data *new_node,
int location)
{
struct personal_data *temp_ptr;
struct personal_data *previous_node;
previous_node = find_node (root, location - 1);
temp_ptr = previous_node->next;
previous_node->next = new_node;
new_node->next = temp_ptr;
}
swap_nodes (struct personal_data *root, int a, int b)
{
int temp;
struct personal_data *node_a;
struct personal_data *node_b;
struct personal_data *temp_node;
if (a > b)
{
temp = a;
a = b;
b = temp;
}
node_b = find_node (root, b);
delete_node (root, b);
node_a = find_node (root, a);
delete_node (root, a);
insert_node (root, node_b, a);
insert_node (root, node_a, b);
}
sort_list (struct personal_data *root)
{
int i, j, list_len, diff;
list_len = list_length (root);
for (i=2; i<=list_len; i++)
{
j = i;
while (strcmp ( (find_node(root, j))->name,
(find_node(root, j-1))->name) < 0)
{
swap_nodes (root, j, j-1);
j--;
}
}
}
print_node (struct personal_data *current_node,
FILE *save_stream)
{
fprintf (save_stream, "%s%s",
current_node->name,
current_node->address);
}
print_list (struct personal_data *current_node,
FILE *save_stream)
{
print_node (current_node, save_stream);
if (current_node->next != NULL)
{
print_list (current_node->next, save_stream);
}
}
struct personal_data *
read_node (FILE *instream)
{
int bytes_read;
int nbytes;
struct personal_data *current_node;
char *name;
char *address;
char *blankline;
int read_err = 0;
current_node = new_empty_node();
nbytes = NAME_LEN;
name = (char *) malloc (nbytes + 1);
bytes_read = getline (&name, &nbytes, instream);
if (bytes_read == -1)
{
read_err = 1;
}
else
{
puts (name);
strncpy (current_node->name, name, NAME_LEN);
free (name);
}
nbytes = ADDR_LEN;
address = (char *) malloc (nbytes + 1);
bytes_read = getline (&address, &nbytes, instream);
if (bytes_read == -1)
{
read_err = 1;
}
else
{
puts (address);
strncpy (current_node->address, address, ADDR_LEN);
free (address);
}
if (read_err)
{
return NULL;
}
else
{
return current_node;
}
}
struct personal_data *
read_file (char *infile)
{
FILE *input_stream = NULL;
struct personal_data *root;
struct personal_data *end_node;
struct personal_data *current_node;
root = new_empty_node();
end_node = root;
input_stream = fopen (infile, "r");
if (input_stream)
{
while (current_node = read_node (input_stream))
{
end_node->next = current_node;
end_node = current_node;
end_node->next = NULL;
}
}
return root;
}
/*
The main function.
Notice how now the only function call needed to process
all command-line options and arguments nicely
is argp_parse.
*/
int
main (int argc, char **argv)
{
struct arguments arguments;
struct personal_data *root;
struct personal_data *end_node;
struct personal_data *current_node;
int i, newnum;
FILE *save_stream;
/* Set argument defaults */
arguments.infile = NULL;
arguments.outfile = NULL;
arguments.verbose = 0;
/* Where the magic happens */
argp_parse (&argp, argc, argv, 0, 0, &arguments);
if (arguments.infile)
{
root = read_file (arguments.infile);
end_node = find_end_node (root);
}
else
{
root = new_empty_node();
end_node = root;
}
/* Where do we send output? */
if (arguments.outfile)
save_stream = fopen (arguments.outfile, "w");
else
save_stream = stdout;
newnum = atoi (arguments.args[0]);
for (i = 1; i <= newnum; i++)
{
current_node = create_node();
end_node->next = current_node;
end_node = current_node;
end_node->next = NULL;
}
sort_list (root);
print_list (root->next, save_stream);
/* Close stream; skip error-checking for brevity of example */
fclose (save_stream);
/* If in verbose mode, print song stanza */
if (arguments.verbose)
{};
return 0;
}