权限字

2个头文件：

• _UAPI_LINUX_STAT_H

#define S_IRWXU 00700//所有者权限
#define S_IRUSR 00400
#define S_IWUSR 00200
#define S_IXUSR 00100

#define S_IRWXG 00070//组权限
#define S_IRGRP 00040
#define S_IWGRP 00020
#define S_IXGRP 00010

#define S_IRWXO 00007
#define S_IROTH 00004
#define S_IWOTH 00002
#define S_IXOTH 00001

• _LINUX_STAT_H

#define S_IRWXUGO   (S_IRWXU|S_IRWXG|S_IRWXO)
#define S_IALLUGO   (S_ISUID|S_ISGID|S_ISVTX|S_IRWXUGO)
#define S_IRUGO     (S_IRUSR|S_IRGRP|S_IROTH)
#define S_IWUGO     (S_IWUSR|S_IWGRP|S_IWOTH)
#define S_IXUGO     (S_IXUSR|S_IXGRP|S_IXOTH)

写个小程序测试一下此权限字是否就是我们ls -l拿到的权限字.

work@vm1:TestKit$ ./test
0111000000,0100000000,0010000000,0001000000
0000111000,0000100000,0000010000,0000001000
0000000111,0000000100,0000000010,0000000001
work@vm1:TestKit$ ls -l test
-rwxrwxr-x 1 work work 9092 Dec 21 17:36 test
work@vm1:TestKit$ chmod g-r test
work@vm1:TestKit$ chmod g-x test
work@vm1:TestKit$ chmod g-w test
work@vm1:TestKit$ ls -l test
-rwx---r-x 1 work work 9092 Dec 21 17:36 test

附：mode_t.cc

#include <stdio.h>
#define S_IRWXU 00700
#define S_IRUSR 00400
#define S_IWUSR 00200
#define S_IXUSR 00100

#define S_IRWXG 00070
#define S_IRGRP 00040
#define S_IWGRP 00020
#define S_IXGRP 00010

#define S_IRWXO 00007
#define S_IROTH 00004
#define S_IWOTH 00002
#define S_IXOTH 00001

#define S_IRWXUGO    (S_IRWXU|S_IRWXG|S_IRWXO)
#define S_IALLUGO    (S_ISUID|S_ISGID|S_ISVTX|S_IRWXUGO)
#define S_IRUGO        (S_IRUSR|S_IRGRP|S_IROTH)
#define S_IWUGO        (S_IWUSR|S_IWGRP|S_IWOTH)
#define S_IXUGO        (S_IXUSR|S_IXGRP|S_IXOTH)

#define Sym(rd, who) S_I##rd##who 
#define Syms(who,f) Sym(R,WX##f),Sym(R,who),Sym(W,who),Sym(X,who)
#define PRUSR do{ printf_bin("%B,%B,%B,%B\n",Syms(USR,U)); }while(0)
#define PRGRP do{ printf_bin("%B,%B,%B,%B\n",Syms(GRP,G)); }while(0)
#define PROTH do{ printf_bin("%B,%B,%B,%B\n",Syms(OTH,O)); }while(0)
#define PRALL PRUSR;PRGRP;PROTH;    


void _pb_clean_plain(char *start, char *end)
{
    if(*start){
        char tmp = *end;
        *end = '\0';
        printf("%s", start);
        *end = tmp;
    }
}

void _pb_pr_byte(unsigned char *p, char *str)
{
    int i = 0;
    while(i < 8){
        str[7 - i] = '0' + ((*p) & (1U << i) ? 1 : 0);
        i++;
    }
}


#include <malloc.h>
void _pb_clean_num(int num)
{
//  printf("%d", num);
    int b = sizeof(num), i;
    char *str = (char *)malloc( b * 8 * sizeof(char));
    unsigned char *p = (unsigned char *)#
    for(i = 0; i < b; i++){
        _pb_pr_byte(p + i, str + 8 * (b - 1 - i));
        //from low to high
    }
//  printf("\n------------\n");
//  for(i = 0; i < b * 8; i++){
//      printf("%d-", *(str + i));
//  }

    printf("%s", str + 22);
    free(str);
}
#include <stdarg.h>
#include <assert.h>
#include <string.h>
#define FORMAT_MAX 4096
void printf_bin(const char *fm, ...)
{
    assert(strlen(fm) < FORMAT_MAX - 1);
    char fm_str[FORMAT_MAX];
    strcpy(fm_str, fm);
    
    va_list args;
    va_start(args,fm);
    char *i = fm_str, *before = fm_str;
    int num;
    while(*i){
        if(*i == '%' && *(i+1) == 'B'){
            _pb_clean_plain(before, i);
            _pb_clean_num(va_arg(args, int));
            i++;
            before = i + 1;
        }
        i++;
    }
    _pb_clean_plain(before, i);
}

int main()
{
    PRALL;
    return 0;
}