文件属性获取

1、getpwuid函数

#include <stdio.h>
#include <sys/types.h>
#include <pwd.h>
int main(int argc, char *argv[])
{uid_t uid = 1000;struct passwd * pw = getpwuid(uid);printf("name:%s gid:%d info:%s wd:%s shell:%s\n",pw->pw_name,pw->pw_gid,pw->pw_gecos,pw->pw_dir,pw->pw_shell);return 0;
}

2、getgruid函数

#include <stdio.h>
#include <sys/types.h>
#include <grp.h>int main(int argc, char *argv[])
{gid_t gid = 1000;struct group * gr= getgrgid(gid);printf("name:%s gid:%d\n",gr->gr_name,gr->gr_gid);return 0;
}

3、time 、 ctime、 localtime

#include <stdio.h>
#include <time.h>
int main(int argc, char *argv[])
{time_t tm;time(&tm);printf("%lu",tm);return 0;
}int main(int argc, char *argv[])
{time_t tm;time(&tm);printf("%s",ctime(&tm));return 0;
}int main(int argc, char *argv[])
{time_t tm;time(&tm);struct tm *tm_info =  localtime(&tm);if(NULL == tm_info){printf("localtime error\n");return 1;}printf("%d-%d-%d %d:%d:%d\n",tm_info->tm_year+1900,tm_info->tm_mon+1,tm_info->tm_mday,tm_info->tm_hour,tm_info->tm_min,tm_info->tm_sec);return 0;
}

4、symlink    link   软链接、硬链接

#include <stdio.h>
#include <unistd.h>
int main(int argc, char *argv[])
{int ret = symlink("./15localtime.c","softlink");if(-1 == ret){printf("symlink error\n");return 1;}return 0;
}int main(int argc, char *argv[])
{int ret = link("./01ls.c","hardlink");if(-1 == ret){printf("link error\n");return 1;}return 0;
}

5、truncate：扩大缩小空间，清零

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
int main(int argc, char *argv[])
{fopen("aaa","w");int ret = truncate("aaa",1024*1024*1024);if(-1 == ret){printf("truncate error\n");return 1;}return 0;
}

6、perror、error、strerror  ：指出错误

#include <stdio.h>
int main(int argc, char *argv[])
{FILE* fp = fopen("12312","r");if(NULL == fp){perror("fopen");return 1;}char buf[256]={0};if(NULL == fgets(buf,sizeof(buf),fp)){perror("fgets");return 1;}else {printf("buf is %s\n",buf);}return 0;
}#include <stdio.h>
#include <error.h>
#include <errno.h>
// errno 
int main(int argc, char *argv[])
{FILE* fp = fopen("12312","r");if(NULL == fp){error(1,errno,"fopen,filename:%s func:%s linenum:%d",__FILE__,__func__,__LINE__);printf("aaa\n");return 1;}return 0;
}#include <stdio.h>
#include <string.h>
int main(int argc, char *argv[])
{int i = 0 ;for(i = 0 ;i<256;i++){printf("%d %s\n",i,strerror(i));}return 0;
}

7、makefile 

src = jisuan.c  //主函数
src += func.c   //额外分装函数
obj = a.out     //执行名
flag = -lm      //链接$(obj):$(src)gcc $(src)-0 $(obj)clean:rm $(obj)