有一个拼写错误，应该是`frprintf`而不是`frprintf`。另外，在`main`函数中没有声明返回类型，默认为`int`，应该显式声明为`void`或`int`。以下是修改后的代码：
```c
/* showmsg--show message queue details */
#include
#include
#include
#include
#include
void mqstat_print(key_t, int, struct msqid_ds *);
int main(int argc, char **argv) {
key_t mkey;
int msg_id;
struct msqid_ds msg_status;
if (argc != 2) {
fprintf(stderr, "usage: showing keyval \n");
exit(1);
}
mkey = (key_t) atoi(argv[1]);
if ((msg_id = msgget(mkey, 0)) == -1) {
perror("msgget failed");
exit(2);
}
if (msgctl(msg_id, IPC_STAT, &msg_status) == -1) {
perror("msgctl failed");
exit(3);
}
mqstat_print(mkey, msg_id, &msg_status);
exit(0);
}
void mqstat_print(key_t mkey, int mqid, struct msqid_ds *mstat) {
printf("\nKey %d, msg_qid %d \n\n", mkey, mqid);
printf("%d message(s) on queue \n\n", mstat->msg_qnum);
printf("Last send by proc %d at %s \n", mstat->msg_lspid, ctime(&(mstat->msg_stime)));
printf("Last recv by proc %d at %s \n", mstat->msg_lrpid, ctime(&(mstat->msg_rtime)));
}
```
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