动态添加到未知大小的char数组

我目前正在进行一项任务，我必须从每个文件中一次一个字符串提取文本，然后将它们连接起来并打印出来。 我找到了一种方法来提取我的角色并将其保存在变量广告中。 如何将这些char添加到我的char数组中以打印到最后？ 我最初将它malloc到一个char的大小，并在每个if语句我realloc。 我在网上找到的所有指南都建议我使用strcat，但我无法传递广告变量来追加。 我该如何解决这个问题？

#include  #include  #include  #include  #include  pthread_mutex_t thread1; pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER; char *output; void* processing(void* file) { FILE *test = fopen("drive1.data", "r"); FILE *drive1 = fopen("drive1.data", "r"); FILE *drive2 = fopen("drive2.data", "r"); FILE *drive3 = fopen("drive3.data", "r"); FILE *drive4 = fopen("drive4.data", "r"); FILE *drive5 = fopen("drive5.data", "r"); int c, a, b, e, d; int control = 0; //Initializingn the char array with initial size 1 output = (char *)malloc(sizeof(char)); while(!feof(drive1)) { if(control == 0) { pthread_mutex_lock(&thread1); //printf("Mutex lock\n"); c = getc(drive1); output = realloc(output, sizeof(output) + sizeof(char)); printf("%c\n", (char)c); strcat(output, (char)c); control++; pthread_mutex_unlock(&thread1); //printf("Mutex unlock\n"); } else if(control == 1) { pthread_mutex_lock(&thread1); //printf("Mutex lock\n"); a = getc(drive2); printf("%c\n", (char)a); control++; pthread_mutex_unlock(&thread1); //printf("Mutex unlock\n"); } else if(control == 2) { pthread_mutex_lock(&thread1); //printf("Mutex lock\n"); b = getc(drive3); printf("%c\n", (char)b); control++; pthread_mutex_unlock(&thread1); //printf("Mutex unlock\n"); } else if(control == 3) { pthread_mutex_lock(&thread1); //printf("Mutex lock\n"); d = getc(drive4); printf("%c\n", (char)d); control++; pthread_mutex_unlock(&thread1); //printf("Mutex unlock\n"); } else if(control == 4) { pthread_mutex_lock(&thread1); //printf("Mutex lock\n"); e = getc(drive5); printf("%c\n", (char)e); control = 0; pthread_mutex_unlock(&thread1); //printf("Mutex unlock\n"); } } } int main() { pthread_t th1; pthread_create(&th1, NULL, processing, NULL); pthread_join(th1, NULL); }