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Top Forums Programming How to check if something exists in linked list in C? Post 302510265 by omega666 on Saturday 2nd of April 2011 01:59:55 PM
Old 04-02-2011
How to check if something exists in linked list in C?

i have a linked list set up like
Code:
typedef struct client_list {
    char *client_name;
    int client_socket_fd;
    struct client_list *next;
} client;

client *client_list=NULL;

before adding to the list i check if it already exists, only if it does not then i add
Code:
if (client_list==NULL || already_there(client_list, buffer)==0) {
    client_list = add_client(buffer, client_list, i);
}

Code:
int already_there(client *client_list, char *username) {
    if (client_list == NULL) return(0);
    else if (strcmp(client_list->client_name, username)==0) return(1);
    else return already_there(client_list->next, username);
}

client *add_client(char *username, client *client_list, int client_socket_fd) {
    client *new_client = (client *)malloc(sizeof(client)); 
    new_client->client_name = username;
    new_client->client_socket_fd = client_socket_fd;
    new_client->next = client_list;
    return new_client;
}

it adds the client the first time, but then the next time, always detects that the new client is already there...
somehow strcmp is always resulting true after the first time...

Last edited by omega666; 04-02-2011 at 03:13 PM..
 

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curs_instr(3X)															    curs_instr(3X)

NAME
instr, innstr, winstr, winnstr, mvinstr, mvinnstr, mvwinstr, mvwinnstr - get a string of characters from a curses window SYNOPSIS
#include <curses.h> int instr(char *str); int innstr(char *str, int n); int winstr(WINDOW *win, char *str); int winnstr(WINDOW *win, char *str, int n); int mvinstr(int y, int x, char *str); int mvinnstr(int y, int x, char *str, int n); int mvwinstr(WINDOW *win, int y, int x, char *str); int mvwinnstr(WINDOW *win, int y, int x, char *str, int n); DESCRIPTION
These routines return a string of characters in str, extracted starting at the current cursor position in the named window. Attributes are stripped from the characters. The four functions with n as the last argument return a leading substring at most n characters long (exclu- sive of the trailing NUL). RETURN VALUE
All of the functions return ERR upon failure, or the number of characters actually read into the string. X/Open defines no error conditions. In this implementation, if the window parameter is null or the str parameter is null, a zero is returned. NOTES
Note that all routines except winnstr may be macros. PORTABILITY
SVr4 does not document whether a length limit includes or excludes the trailing NUL. The ncurses library extends the XSI description by allowing a negative value for n. In this case, the functions return the string ending at the right margin. SEE ALSO
curses(3X). curs_instr(3X)
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