Linux下C编程-----IO/文件操作 模拟linux ls程序显示文件系统树形结构(2)

Linux下的IO/文件操作练习,知识虽然简单 但是往往基础容易被忽略,偶尔的练习是有必要的。

      

练习printf

/*************************************************************************> File Name: printf.c> Author: > Mail: > Created Time: Wed 11 Feb 2015 01:08:15 AM PST ************************************************************************/#include<stdio.h>int main(){     printf("%10s\n","hello");    printf("%-10s\n","hello");    printf("%s\n","hello") ;    printf("%*s\n",10,"hello") ;    printf("%010d\n",100) ;    printf("%10.4g\n",1.22) ;    printf("%10s\n","Hello,I am a programmer !") ;    return 0 ;}

练习C标准库的文件复制 相比系统调用  会快 因为有缓冲

/*************************************************************************> File Name: cpy.c> Author: > Mail: > Created Time: Wed 11 Feb 2015 01:37:56 AM PST ************************************************************************/#include<stdio.h>int main(){       int c;    FILE*in=fopen("./printf","r");    FILE*out=fopen("./printf_tem","w");    while((c=fgetc(in))!=EOF)    {        fputc(c,out) ;    }    exit(0);}

练习查看一个文件的状态

/*************************************************************************> File Name: fileinfo.c> Author: > Mail: > Created Time: Wed 11 Feb 2015 11:25:21 PM PST ************************************************************************/#include<stdio.h>#include<sys/stat.h>#include<unistd.h> int main(){    int fileNo;   struct  stat fileStat ;   FILE*pFile= fopen("./cpy","r");   if(pFile==NULL)    {        printf("File Open Error!\n") ;        exit(0);    }   fileNo= fileno(pFile);   printf("FileNumber:%d\n",fileNo) ;  if(-1==fstat(fileNo,&fileStat))    {        printf("GetFileInfo Error!\n") ;        exit(0) ;    }    printf("DeviceID:%d\n",fileStat.st_dev);    printf("UserID:%d\n",fileStat.st_uid);    printf("GroupID:%d\n",fileStat.st_gid);    printf("FileSize:%d\n",fileStat.st_size);    return 0 ;}

我们模拟Linux下的ls程序 

/*************************************************************************> File Name: listdir.c> Author: > Mail: > Created Time: Thu 12 Feb 2015 12:49:13 AM PST ************************************************************************/#include<stdio.h>#include<unistd.h>#include<sys/stat.h>#include<dirent.h>#include<string.h>#include<sys/types.h>void list_func(char*path,int depth)  {      DIR*pDirHandle= opendir(path);    struct dirent * dent ;    struct stat  fstat ;    if(pDirHandle==NULL)    {        printf("OpenDir %s  Error!\n",path);        exit(0);    }   chdir(path);    while((dent=readdir(pDirHandle))!=NULL)    {          //error then return -1         lstat(dent->d_name,&fstat);        if(S_ISDIR(fstat.st_mode))        {              //remove director . and ..            if(strcmp(".",dent->d_name)==0||              strcmp("..",dent->d_name)==0 )                continue ;            printf("%*s%s/\n",depth,"",dent->d_name) ;            list_func(dent->d_name,depth+4) ;        }else           printf("%*s%s\n",depth,"",dent->d_name);             }    chdir("..");    closedir(pDirHandle);}int main(int argc,char**argv){       if(argc<2)    {        printf("Param Format:  listdir path\n");        return ;    }    char*pDirPath=argv[1];    int depath=0;    printf("List Begin:\n");    list_func(pDirPath,depath) ;    printf("List End.\n");    return 0 ;}

格式化错误代码

/*************************************************************************> File Name: errformat.c> Author: > Mail: > Created Time: Fri 13 Feb 2015 12:50:00 AM PST ************************************************************************/#include<stdio.h>#include<errno.h>#include<stdlib.h>#include<string.h>int main(){      char* message=NULL ;    //error    fopen("aaaaa","r")  ;    // printf(strerror(errno));    message=strerror(errno);    if(message!=NULL)        printf("Error:%s\n",message);    perror("Program:");    return 0;}