liunx 第一章

 第一章  基础知识

 目录  文件  路径

#include "ourhdr.h"

#include <sys/types.h>

#include <dirent.h>

//查找文件夹内容

int main(int argc,char** argv)

{

   DIR *dp;  //指向文件的指针  typedef struct __dirstream DIR;

   struct dirent *dirp;

   if(argc !=2)

       err_quit("a single argument (the directory");  //出错提示

   if((dp = opendir(argv[1])) ==NULL)    //opendir  返回指向dir结构体的指针

       err_sys("can‘t open %s",argv[1]);

   while((dirp = readdir(dp))!=NULL)  //循环调用readdir

   {

       printf("%sn",dirp->d_name);

       //

   }

   printf("%sn",dirp->d_type);

   closedir(dp); //关闭文件

   exit(0);

    return 0;

}

不用缓存的IO

函数: open read write  lseek close

#include "ourhdr.h"

#define BUFFERSIZE 8192

int main(void)

{

    int n;

    char buf[BUFFERSIZE];

    while((n=read(STDIN_FILENO,buf,BUFFERSIZE)))  //从总端读取字符

        if(write(STDIN_FILENO,n)!=n)  //把字符写入终端

            err_sys("write error");

    if(n<0)

        err_sys("read error");

    exit(0);

}

#include "ourhdr.h"

int main(void)

{

    int c;

    while((c=getc(stdin))!=EOF)//读取一个字节

        if(putc(c,stdout)==EOF)

            err_sys("output error");

    if(ferror(stdin))

        err_sys("input error");

    putc(EOF,stdout);  //END OF FILE

    exit(0);

}

进程控制的主要函数: fork  exec waitpid

#include "ourhdr.h"

int main(void)

{

    char buf[MAXSIZE];

    pid_t pid;

    int status;

    printf("%% ");

    while(fgets(buf,MAXSIZE,stdin)!=NULL)  //从终端读入字符

    {

        buf[strlen(buf)-1] = 0;//

        if((pid=fork())<0)

            err_sys("fork error");

        else if(pid ==0 )

        {

            execlp(buf,(char*)0);  //执行buf

            err_ret("could‘t execte :%s ",buf);

            exit(127);

        }

        if((pid = waitpid(pid,&status,0))<0)

            err_sys("waitpid error");

        printf("%% ");

    }

    exit(0);

}

#include "ourhdr.h"

int main(int argc,char** argv)

{

    fprintf(stderr,"EACCES:%sn",strerror(EACCES));

    errno = ENOENT;

    perror(argv[0]);

    exit(0);

}

#include "ourhdr.h"

static void sig_int(int);  //our signal-catching function

int main(void)

{

    char buf[MAXLINE];

    pid_t pid;

    int status;

    if(signal(SIGINT,sig_int) == SIG_ERR) //参数1 要处理的信号  参数2 处理方式

        err_sys("signal error");

    printf("%% ");

    while(fgets(buf,MAXLINE,stdin)!=NULL)

    {

        buf[strlen(buf)-1]=0;

    if((pid = fork())<0)

        err_sys("fork error");

    else if (pid ==0)

    {

        execlp(buf,(char*)0);

        err_ret("couldn‘t execute: %s",buf);

        exit(127);

    }

    if((pid = waitpid(pid,0))<0)

        err_sys("waitpid error");

    printf("%% ");

    }

    exit(0);

}

void sig_int(int signo)

{

    printf("interrupt n%%");

}