GNU readline

GNU readline implement filename auto-complete by default, it will list all the files in the current directory. We can disable it by binds our TAB key to some other operation. In , I simply abort the operation to ignore users hitting TABs.

Auto-complete are useful if only we can customize it. Well, readline allows us do it by assign our own callback functions. First of all, you may want to read up the manual from . It does provides a c sample codes as well but I find it too complicated, here I provide a simplified version that can be compiled under c++.

#include
#include
#include
#include

static char** my_completion(const char*, int ,int);
char* my_generator(const char*,int);
char * dupstr (char*);
void *xmalloc (int);

char* cmd [] ={ "hello", "world", "hell" ,"word", "quit", " " };

int main()
{
    char *buf;

    rl_attempted_completion_function = my_completion;

    while((buf = readline("\n >> "))!=NULL) {
        //enable auto-complete
        rl_bind_key('\t',rl_complete);

        printf("cmd [%s]\n",buf);
        if (strcmp(buf,"quit")==0)
            break;
        if (buf[0]!=0)
            add_history(buf);
    }

    free(buf);

    return 0;
}


static char** my_completion( const char * text , int start,  int end)
{
    char **matches;

    matches = (char **)NULL;

    if (start == 0)
        matches = rl_completion_matches ((char*)text, &my_generator);
    else
        rl_bind_key('\t',rl_abort);

    return (matches);

}

char* my_generator(const char* text, int state)
{
    static int list_index, len;
    char *name;

    if (!state) {
        list_index = 0;
        len = strlen (text);
    }

    while (name = cmd[list_index]) {
        list_index++;

        if (strncmp (name, text, len) == 0)
            return (dupstr(name));
    }

    /* If no names matched, then return NULL. */
    return ((char *)NULL);

}

char * dupstr (char* s) {
  char *r;

  r = (char*) xmalloc ((strlen (s) + 1));
  strcpy (r, s);
  return (r);
}

void * xmalloc (int size)
{
    void *buf;

    buf = malloc (size);
    if (!buf) {
        fprintf (stderr, "Error: Out of memory. Exiting.'n");
        exit (1);
    }

    return buf;
}