Differences between sizeof and strlen

 

#include <stdio.h>#include <string.h>int main (int argc, char **argv){    char *a = "0123456789";    char b[] = "0123456789";    char c[100] ="0123456789";    int d[100] ={0,1,2,3,4,5,6,7,8,9};    char e[8] = "abc0\0e123\0ed3\0f";

    char f[] = "abc\\nt\012\xa1*2";    printf("char *a = \"%s\"\n",a);    printf("char b[] = \"%s\"\n",b);    printf("char c[100] = \"%s\"\n",c);    printf("int d[100] = \"%s\"\n",d);    printf("int e[8] = \"%s\"\n",e);

    printf("int f[] = \"%s\"\n",f);

    printf("--------------------\n");    printf("sizeof(a) = %d\n",sizeof(a));    printf("strlen(a) = %d\n",strlen(a));    printf("sizeof(b) = %d\n",sizeof(b));    printf("strlen(b) = %d\n",strlen(b));    printf("sizeof(c) = %d\n",sizeof(c));    printf("strlen(c) = %d\n",strlen(c));    printf("sizeof(d) = %d\n",sizeof(d));    printf("strlen(d) = %d\n",strlen(d));    printf("sizeof(e) = %d\n",sizeof(e));    printf("strlen(e) = %d\n",strlen(e));

    printf("sizeof(f) = %d\n",sizeof(f));

    printf("strlen(f) = %d\n",strlen(f));} /* ----- End of main() ----- */

 

Output:

[[Email protected] ~ /Coder] $ GCC 6-3.c 6-3.c: In the 'main' function: 6-3.c: 29: warning: the string used to initialize the character array is too long 6-3.c: 44: Warning: when the first parameter of 'strlen' is passed, it is converted between incompatible pointer types/usr/include/string. h: 399: Note: The 'const char * 'type is required, but the real parameter type is 'int *' [email protected] ~ /Coder] $. /. out char * A = "0123456789" char B [] = "0123456789" char C [100] = "0123456789" int d [100] = "" int e [8] =" abc0 "-------------------- sizeof () = 4 strlen (A) = 10 sizeof (B) = 11 strlen (B) = 10 sizeof (c) = 100 strlen (c) = 10 sizeof (d) = 400 strlen (d) = 0 sizeof (e) = 8 strlen (e) = 4

sizeof(f) = 11 

strlen(f) = 10

 

The above examples can be summarized as follows:

Sizeof:

1. Operator.

2. It is used to calculate the pre-allocated size in the memory. Therefore, we can use sizeof to define the array dimension during pre-compilation.

3. sizeof (d) = 400 indicates that the array size is the product of each dimension * the size of the array element.

4. sizeof (e) = 8 we can see that the size of the array in the memory is based on the dimension, rather than subsequent initialization and assigned values.

Strlen:

1. It is a function. The header file is <string. h>

2. The strlen result can be calculated only during running. It is used to calculate the length of a string (it must end with "\ 0"), rather than the memory size occupied by the type.

3. strlen (e) = 4 indicates that strlen calculates the length of a string based on "\ 0.

 

The number of bytes occupied by the String constant "ABC \ nt \ 012 \ xA1 * 2" in the memory is

Abc -- 3
\ -- 1 Escape Character
NT -- 2
\ 012 -- 1 octal number
\ XA1 -- 1 hexadecimal number
* 2 -- 2
There is also a string Terminator. A total of 11 bytes.

Differences between sizeof and strlen