I am working on a command line interpretter for linux.(I use fedora
core 1 and am coding in c).I am trying to implement the history
features for the commans typed at the command line.I am using the
<readline/readline.h> &
<readline/history.h> header files.When i try to compile the following
program (given in gnu manual) using gcc or cc compilers I get the
following error (though i have included all the necessary header
files,including the ones mentioned above:

/tmp/ccmh5Xy8.o(.text+0x25): In function `main':
: undefined reference to `using_history'
/tmp/ccmh5Xy8.o(.text+0x107): In function `main':
: undefined reference to `history_expand'
/tmp/ccmh5Xy8.o(.text+0x16d): In function `main':
: undefined reference to `add_history'
/tmp/ccmh5Xy8.o(.text+0x1f0): In function `main':
: undefined reference to `write_history'
/tmp/ccmh5Xy8.o(.text+0x220): In function `main':
: undefined reference to `read_history'
/tmp/ccmh5Xy8.o(.text+0x248): In function `main':
: undefined reference to `history_list'
/tmp/ccmh5Xy8.o(.text+0x29c): In function `main':
: undefined reference to `history_base'
/tmp/ccmh5Xy8.o(.text+0x307): In function `main':
: undefined reference to `remove_history'
collect2: ld returned 1 exit status

The program is as follows:

#include <stdio.h>
#include <readline/history.h>



main (argc, argv)
int argc;
char **argv;
{
char line[1024], *t;
int len, done = 0;

line[0] = 0;

using_history ();
while (!done)
{
printf ("history$ ");
fflush (stdout);
t = fgets (line, sizeof (line) - 1, stdin);
if (t && *t)
{
len = strlen (t);
if (t[len - 1] == '\n')
t[len - 1] = '\0';
}

if (!t)
strcpy (line, "quit");

if (line[0])
{
char *expansion;
int result;

result = history_expand (line, &expansion);
if (result)
fprintf (stderr, "%s\n", expansion);

if (result < 0 || result == 2)
{
free (expansion);
continue;
}

add_history (expansion);
strncpy (line, expansion, sizeof (line) - 1);
free (expansion);
}

if (strcmp (line, "quit") == 0)
done = 1;
else if (strcmp (line, "save") == 0)
write_history ("history_file");
else if (strcmp (line, "read") == 0)
read_history ("history_file");
else if (strcmp (line, "list") == 0)
{
register HIST_ENTRY **the_list;
register int i;

the_list = history_list ();
if (the_list)
for (i = 0; the_list[i]; i++)
printf ("%d: %s\n", i + history_base, the_list[i]->line);
}
else if (strncmp (line, "delete", 6) == 0)
{
int which;
if ((sscanf (line + 6, "%d", &which)) == 1)
{
HIST_ENTRY *entry = remove_history (which);
if (!entry)
fprintf (stderr, "No such entry %d\n", which);
else
{
free (entry->line);
free (entry);
}
}
else
{
fprintf (stderr, "non-numeric arg given to `delete'\n");
}
}
}
}

Your help will be greatly appreciated.
gautamshetty

Do you link with -lreadline? Including headers will only supply declarations. It's the library that gives you definitions.

I will try it out and keep you posted.Thanks for the reply.

gautamshetty

Thanks eggbert!
yeah including -lreadline worked.thanks for the help pal.
gautamshetty