Android系统在shell中的df命令实现

root@android:/ # dfFilesystem       Size  Used  Free  Blksize/dev         446.8M 36.0K 446.8M  4096/mnt/secure      446.8M 0.0 K 446.8M  4096/mnt/asec       446.8M 0.0 K 446.8M  4096/mnt/cart0      446.8M 0.0 K 446.8M  4096/mnt/obb       446.8M 0.0 K 446.8M  4096/system        1.5 G 376.6M 1.1 G  1024/data         5.2 G 188.9M 5.0 G  4096/cache        124.0M 16.1M 107.9M  4096/mnt/.cci       503.9M 16.4M 487.6M  4096/storage/sdcard0   5.2 G 188.9M 5.0 G  4096/mnt/external_sd   7.5 G 475.0M 7.0 G  4096

#include <stdio.h>#include <stdlib.h>#include <string.h>#include <errno.h>#include <sys/statfs.h>static int ok = EXIT_SUCCESS;//根据挂载的文件的大小来计算static void printsize(long double n){  char unit = 'K';  n /= 1024;  if (n > 1024) {    n /= 1024;    unit = 'M';  }  if (n > 1024) {    n /= 1024;    unit = 'G';  }  printf("%-4.1Lf%c", n, unit);}static void df(char *s, int always) { //  struct statfs st; //statfs函数可用来查询文件系统相关的信息。  if (statfs(s, &st) < 0) {    fprintf(stderr, "%s: %s/n", s, strerror(errno));    ok = EXIT_FAILURE;  } else {    if (st.f_blocks == 0 && !always)      return;        printf("%-20s ", s);    printsize((long double)st.f_blocks * (long double)st.f_bsize);    printf(" ");    printsize((long double)(st.f_blocks - (long double)st.f_bfree) * st.f_bsize);    printf(" ");    printsize((long double)st.f_bfree * (long double)st.f_bsize);    printf("  %d/n", (int) st.f_bsize);  }}int df_main(int argc, char *argv[]) {  printf("Filesystem       Size  Used  Free  Blksize/n");  if (argc == 1) {    char s[2000]; //挂载的文件都在/proc/mounts下显示    FILE *f = fopen("/proc/mounts", "r");    while (fgets(s, 2000, f)) {      char *c, *e = s;      for (c = s; *c; c++) {        if (*c == ' ') {          e = c + 1;          break;        }      }      for (c = e; *c; c++) {        if (*c == ' ') {          *c = '/0';          break;        }      }      df(e, 0);    }    fclose(f);  } else {    int i;    for (i = 1; i < argc; i++) {      df(argv[i], 1);    }  }  exit(ok);}