下面是一个Python程序的例子，它从一个.txt文件中读取一个社交网络，并根据共同的好友为用户推荐好友：

def read_file(file_name):
    with open(file_name, "r") as file:
        lines = file.readlines()
        num_of_users = int(lines[0].strip())
        friends = {}
        for i in range(1, num_of_users + 1):
            user_friends = lines[i].strip().split()
            friends[user_friends[0]] = user_friends[1:]
    return friends

def suggest_friends(friends):
    suggested_friends = {}
    for user, friend_list in friends.items():
        suggested_friends[user] = []
        for friend in friend_list:
            suggested_friends[user] += [f for f in friends[friend] if f != user and f not in friend_list and f not in suggested_friends[user]]
    return suggested_friends

def main():
    friends = read_file("network.txt")
    suggested_friends = suggest_friends(friends)
    for user, suggested in suggested_friends.items():
        print(f"{user} should be friends with {', '.join(suggested)}")

if __name__ == "__main__":
    main()

这段代码逐行读取.txt文件，并将用户之间的关系存储在字典中。然后，代码通过检查每个朋友的朋友并添加那些还不是朋友和还没有被建议为朋友的朋友来为每个用户建议朋友。代码为每个用户打印建议的朋友。