說明

常用 C Commands 記錄

通用

清空

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
void main()
{
    // 清空字串
    char sourceStr[20]
    memset(sourceStr,0,20);

    // 清空 structure
    struct Member member;
    memset(&member, 0x00, sizeof(struct Member));

    // 指標類的 struct 尚未 malloc 時不能清空
    struct Member *memberPoint;

    // 指標類的 struct malloc 後，就可以清空
    // 記憶體分配空間後就可以進行清空
    struct Member *memberPoint1 = malloc(sizeof(struct Member));
    memset(memberPoint1, 0x00, sizeof(struct Member));

}

轉換

1
2
3
4
5
6
7
8
9
10
11
void main()
{
    // string -> int
    char sourceStr[3] = "30";
    int result = (int)strtol(&sourceStr, (char**)NULL, 10);
    printf("%d\n",result);

    char *sourceStr = "30";
    int result = (int)strtol(sourceStr, (char**)NULL, 10);
    printf("%d\n",result);
}

字串

計算長度

1
2
3
4
5
6
void main()
{
    char *str = "lentgh";
    // length is '6'
    printf("length is '%d'\n",strlen(str));
}

寫字串進 array

1
2
3
4
5
6
7
8
9
10
11
void main()
{
    char sourceStr[20] = {0};
    char *targetStr = "target string";
    // 寫字串並帶 format
    snprintf(sourceStr,20,"x%sx",targetStr);
    // 最好加上結束字元
    sourceStr[strlen(sourceStr)] = 0x00;
    // source string is 'xtarget stringx'
    printf("source string is '%s'\n",sourceStr);
}

對比字串

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
void main()
{
    char *sourceStr = "string source";
    char *targetStr = "string target";
    // 完整比對
    if (strlen(sourceStr) == strlen(targetStr) 
        && (0 == strncmp(sourceStr, targetStr, strlen(sourceStr)))){ // 或 memcmp(sourceStr, targetStr, strlen(sourceStr)) 都可以
        printf("exactly equal\n");
    } else {
        // √
        printf("possibly unequal lengths or comparison failed\n"); 
    }

    // include
    if (strstr(sourceStr,"source")){
        // √
        printf("the sourceStr exist source term\n");
    } else {
        printf("not found\n");
    }
}

在 String Array 中比對是否存在

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
void main(){
    char *stringArray[] = {
        "Current",
        "Energy",
        "Power",
        "Voltage",
        NULL,
    };
    char **stringItem;
    char *sourceKey = "Power";
    for(stringItem = (char **)stringArray ; *stringItem ; ++stringItem){
        if (strlen(sourceKey) == strlen(*stringItem) &&  0 == strncmp(sourceKey, *stringItem,strlen(sourceKey))){
            // the stringArray exist 'Power'
            printf("the stringArray exist '%s'\n",*stringItem);
            break;
        } 
    }
}

在 String Array 中加入值在尾端

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
void main(){
    // 因為要 resize 所以一定要用 malloc ，如果是 char* array[] 這種是沒辦法 realloc 的
    char** stringArray = malloc(5 * sizeof(char*));
    if (stringArray){
        stringArray[0] = "Current";
        stringArray[1] = "Energy";
        stringArray[2] = "Power";
        stringArray[3] = "Voltage";
    }

    int count =0;
    char **stringItem;
    for(stringItem = (char **)stringArray ; *stringItem ; ++stringItem){
        count++;
    }
    stringArray = realloc(stringArray,sizeof(char*)*(count+2));
    stringArray[count++] = "Test";
    stringArray[count++] = NULL;
    for(stringItem = (char **)stringArray ; *stringItem ; ++stringItem){
        // array string is 'Current'
        // array string is 'Energy'
        // array string is 'Power'
        // array string is 'Voltage'
        // array string is 'Test'
        printf("array string is '%s'\n",*stringItem);
    }
}

復製字串

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
void main()
{
    char sourceStr[20] = {0};
    char *targetStr = "string target";
    // new string is 'string tar'
    printf("new string is '%s'\n",strncpy(sourceStr,targetStr,10));

    // 要復製的目標是指標時，可以改用 strndup
    char *sourceStr;
    char *targetStr = "string target";
    sourceStr = strndup(targetStr,10);
    // new string is 'string tar'
    printf("new string is '%s'\n",sourceStr);
    // 用完後記得 free 掉
    free(sourceStr);
}

接字串在字尾

1
2
3
4
5
6
7
void main()
{
    char sourceStr[20] = "string source";
    char *targetStr = "string target";
    // new string is 'string sourcestring tar'
    printf("new string is '%s'\n",strncat(sourceStr,targetStr,10));
}

切割字串

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
void main()
{
    char source[8] = "a.b.c.d";
    char *pToken;
    pToken = strtok(&source, ".");
    while(pToken != NULL)
    {
        // the token is 'a'
        // the token is 'b'
        // the token is 'c'
        // the token is 'd'
        printf("the token is '%s'\n",pToken);
        pToken = strtok(NULL, ".");
    }
}

Struct

初使化

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
struct _member{
    char name[20];
    int age;
};
typedef struct _member member;
void main()
{
    // 非指標類
    member m1;
    memset(&m1, 0x00, sizeof(member));
    m1.age = 18;
    
    // 指標
    member* m2 = malloc(sizeof(member));
    memset(m2, 0x00, sizeof(member));
    m2->age = 28;
}

復製 Struct

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
struct _member{
    char name[20];
    int age;
};
typedef struct _member member;
void main()
{
    // 非指標類
    member m1;
    memset(&m1, 0x00, sizeof(member));
    m1.age = 18;
    
    // 指標
    member* m2 = malloc(sizeof(member));
    memset(m2, 0x00, sizeof(member));
    m2->age = 28;

    // Copy
    memcpy(m2,&m1,sizeof(member));
    // m2 age is '18'
    printf("m2 age is '%d'\n",m2->age);
}

對比 Struct

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
struct _member{
    char name[20];
    int age;
};
typedef struct _member member;
void main()
{
    // 非指標類
    member m1;
    memset(&m1, 0x00, sizeof(member));
    m1.age = 18;
    
    // 指標
    member* m2 = malloc(sizeof(member));
    memset(m2, 0x00, sizeof(member));
    m2->age = 28;

    // Compare
    if (0 == memcpy(m2,&m1,sizeof(member))){
        printf("exactly equal\n");
    } else {
        //√ unequal different count is '10'
        printf("unequal different count is '%d'\n",memcpy(m2,&m1,sizeof(member))); 
    }
}