How to check if the string is already in an array of structures?

Question

How to check if the string is already in an array of structures? The array is inside a structure and I don't know how to compare arrays inside the structure in C.

#include <stdio.h>
#include <string.h>

struct song {
    char title[30];
    char artist[30];
    char album[30];
};

typedef struct playlist {
    char sname[30];
    char asongs[10];
    int scount;

    struct song music;
} songlist;

void addPlaylist(struct playlist *menu, int i) {
    printf("Enter playlist name: ");
    scanf("%s", menu[i].sname);

    for (int j = 0; j < i; j++) {
        if (strcmp(menu[i].sname, menu[j].sname) == 0) {
            printf("already exists!\n");
        } else {
            printf("Successfully added playlist!\n");
        }
    }
}

int main() {
   //menu. if choice == 1, go to addPlaylist func
}

I am asking the user for the name of playlist, and when a string is entered, it should be on the array sname.

When the user wants to add another playlist and enters a playlist name that is already in the array sname, the program should print already exists!; otherwise, it should add on the array.

The array is inside a structure and I'm trying to compare the arrays to check if the user's input (which is a string) already exists inside the array. I tried using for loop but I am not sure about my conditions and the components inside the strcmp function.

EDIT For example, if the user already entered multiple names like:

favorites
vibes
mood

and then, the user decided to add more playlist names then accidentally entered the name vibes which already exists in the array.

If vibes already exists, I want the program to print already exists!

I want to know how to properly check if the entered string already exists (especially if the string is inside a structure).

EDIT

Here's the output:

As you can see there's also problem in printing the successfully... and already...

Answer 1

The code which demonstrates the requested adding behavior. See in-code comments for details.

#include <stdio.h>
#include <string.h>

struct song {
    char title[30];
    char artist[30];
    char album[30];
};

typedef struct playlist {
    char sname[30];
    char asongs[10];
    int scount;

    struct song music;
} songlist;

void addPlaylist(struct playlist *menu, int i) {
    char sname[30]; // use local variable for new input
    printf("Enter playlist name: ");
    scanf("%s", sname); // read into local variable

    // go over all lists to check if it already exists
    for(int j=0; j<i; j++) {
        if(strcmp(sname, menu[j].sname)==0) {
            printf("Playlist '%s' already exists!\n", sname);
            return;
        } 
    }

    // go over all lists to search for first empty entry
    for(int j=0; j<i; j++) {
        if(menu[j].sname[0] == '\0') {
            strcpy(menu[j].sname, sname);
            printf("Successfully added playlist '%s'!\n", menu[j].sname);
            return;
        } 
    }

    // No empty entry found
    printf("No space for new Playlist. Please remove one!\n");
}

int main() {
    songlist playlists[10];
    for (int i=0; i<10; i++) {
        playlists[i].sname[0] = '\0'; // use string termination char to indicate unused entry
        playlists[i].asongs[0] = '\0';
        playlists[i].scount = 0;
        playlists[i].music.title[0] = '\0';
        playlists[i].music.album[0] = '\0';
        playlists[i].music.artist[0] = '\0';
    }
    char input;
    do {
        printf("======= MENU =======\n");
        printf("[1] Add Playlist\n");
        printf("[2] Add Song to Playlist\n");
        printf("[3] Remove Song from Playlist\n");
        printf("[4] View a Playlist\n");
        printf("[5] View All Data\n");
        printf("[6] Exit\n");
        scanf(" %c", &input);

        switch (input) {
            case '1': addPlaylist(playlists, 10); break;
            case '2': break;
            case '3': break;
            case '4': break;
            case '5': break;
            case '6': break;
            default: printf("Unknown selection!\n"); break;
        }
    } while (input != '6');

   return 0;
}

$ gcc -Wall playlist.c
$ ./a.out
======= MENU =======
[1] Add Playlist
[2] Add Song to Playlist
[3] Remove Song from Playlist
[4] View a Playlist
[5] View All Data
[6] Exit
1
Enter playlist name: vibes
Successfully added playlist 'vibes'!
======= MENU =======
[1] Add Playlist
[2] Add Song to Playlist
[3] Remove Song from Playlist
[4] View a Playlist
[5] View All Data
[6] Exit
1
Enter playlist name: mood
Successfully added playlist 'mood'!
======= MENU =======
[1] Add Playlist
[2] Add Song to Playlist
[3] Remove Song from Playlist
[4] View a Playlist
[5] View All Data
[6] Exit
1
Enter playlist name: favorites
Successfully added playlist 'favorites'!
======= MENU =======
[1] Add Playlist
[2] Add Song to Playlist
[3] Remove Song from Playlist
[4] View a Playlist
[5] View All Data
[6] Exit
1
Enter playlist name: vibes
Playlist 'vibes' already exists!
======= MENU =======
[1] Add Playlist
[2] Add Song to Playlist
[3] Remove Song from Playlist
[4] View a Playlist
[5] View All Data
[6] Exit
6
$ 

Answer 2

There is a problem in addPlaylist: you should return from the function when you find a match, returning 0 to the caller so it does not add the last entry, and you should test all entries before printing Successfully added playlist!, returning 1 to the caller.

// return 1 if the playlist was added at offset i
int addPlaylist(struct playlist *menu, int i) {
    char sname[30];

    printf("Enter playlist name: ");
    if (scanf("%29s", sname) != 1)
        return 0;

    for (int j = 0; j < i; j++) {
        if (strcmp(sname, menu[j].sname) == 0) {
            printf("already exists!\n");
            return 0;
        }
    }
    strcpy(menu[i].sname, sname);
    printf("Successfully added playlist!\n");
    return i;
}