我遇到的问题是该程序是菜单驱动的。当我输入字母“ i”时，将在大小为input的MAX_LENGTH+1数组中输入。通过GDB，我发现在input数组的第0个索引中输入了“ i”，其余的空格都用NULL_CHAR字符输入了。无论如何，当我在插入菜单中按“ i”时，我都会被一个字段打招呼，告诉我输入一个值。我输入任何整数，然后按inter。它没有告诉我“ Command ?:”字段，而是给我机会输入一个条目，而是立即告诉我我的输入无效，并告诉我再次输入命令。这是我的意思：
Commands are I (insert), D (delete), S (search by name),
V (search by value), P (print), Q (quit).
Command?: i
45
Command?:
Invalid command.
Commands are I (insert), D (delete), S (search by name),
V (search by value), P (print), Q (quit).
Command?:
我发现发生这种情况的原因是因为再次调用safegets函数时，出于某种原因，函数safegets中的局部变量
c的值为NULL_CHAR，这可能是由于以下事实导致的：输入char数组的所有其他条目都为NULL_CHAR。我不明白为什么c会自动分配NULL_CHAR的值，因为在while循环中，因为有一条语句c = getchar()应该再次询问我的输入。但是由于某种原因，每次输入后，c的默认值都将变为NULL_CHAR，并在下次调用safegets时要求您输入。这是我希望输出的样子：
Commands are I (insert), D (delete), S (search by name),
V (search by value), P (print), Q (quit).
Command?: I
value: 50000
Command?: I
value:
这是主要功能：
const int MAX_LENGTH = 1023;
const char NULL_CHAR = '\0';
const char NEWLINE = '\n';
int main (void)
{
const char bannerString[]
= "Personal Team Maintenance Program.\n\n";
const char commandList[]
= "Commands are I (insert), D (delete), S (search by name),\n"
" V (search by value), P (print), Q (quit).\n";
// Declare linked list head.
// ADD STATEMENT(S) HERE TO DECLARE LINKED LIST HEAD.
// announce start of program
printf("%s",bannerString);
printf("%s",commandList);
char response;
char input[MAX_LENGTH+1];
int value;
do
{
printf("\nCommand?: ");
safegets(input,MAX_LENGTH+1);
// Response is first char entered by user.
// Convert to uppercase to simplify later comparisons.
response = toupper(input[0]);
if (response == 'I')
{
// Insert a player entry into the linked list.
// Maintain the list in correct order (G, D, M, S).
// ADD STATEMENT(S) HERE
// USE THE FOLLOWING PRINTF STATEMENTS WHEN PROMPTING FOR DATA:
// printf(" family name: ");
// printf(" first name: ");
// printf(" position: ");
printf(" value: ");
scanf("%d", value);
}
else if (response == 'D')
{
// Delete a player from the list.
printf("\nEnter family name for entry to delete: ");
// ADD STATEMENT(S) HERE
}
else if (response == 'S')
{
// Search for a player by family name.
printf("\nEnter family name to search for: ");
// ADD STATEMENT(S) HERE
}
else if (response == 'V')
{
// Search for players that are worth less than or equal a value.
printf("\nEnter value: ");
// ADD STATEMENT(S) HERE
}
else if (response == 'P')
{
// Print the team.
// ADD STATEMENT(S) HERE
}
else if (response == 'Q')
{
; // do nothing, we'll catch this case below
}
else
{
// do this if no command matched ...
printf("\nInvalid command.\n%s\n",commandList);
}
} while (response != 'Q');
// Delete the whole linked list that hold the team.
// ADD STATEMENT(S) HERE
// Print the linked list to confirm deletion.
// ADD STATEMENT(S) HERE
return 0;
}
辅助函数被调用：
void safegets (char s[], int arraySize)
{
int i = 0, maxIndex = arraySize-1;
char c;
while (i < maxIndex && (c = getchar()) != NEWLINE)
{
s[i] = c;
i = i + 1;
}
s[i] = NULL_CHAR;
}
最佳答案
您的代码很好。你需要改变
scanf("%d", value);
// ^Place & before the argument value because scanf expect pointer as its argument
至
scanf("%d", &value);