/*
????本程序模擬cat命令（只模擬打印，不處理特殊字符）

????歷史記錄:
????日期????????????作者????????????描述????????????聯系方式
????20140417????????盧富波??????????首次創建????????1164830775@qq.com

????需求:
????僅僅只是將數據打印到標準輸出，不對數據中的特殊字符進行處理
????如果沒輸入任何參數，或者輸入的文件名為-則從標準輸入讀數據
*/
#include??????/*?for?printf?*/
#include?????/*?for?exit?*/
#include?
#include?
#include?
#include?
#include?
#include?

#define?????EXIT_FAILURE????????????1
#define?????EXIT_SUCESS?????????????0
#define?????MAX_BUF_SIZE????????????1024

static?char?????????????*program_name?=?NULL;???/*?程序名指針???????????????*/
static?char?????????????*infile?=?NULL;?????????/*?指向輸入文件?????????????*/
static?int??????????????input_desc?=?-1;????????/*?輸入文件描述符???????????*/
static?int??????????????exit_status?=?EXIT_FAILURE;?/*?命令退出狀態?????????????*/

static?void
usage（int?status）
{
????if（status?!=?0）{
????????fprintf（stderr?“Try?‘%s?--help‘?for?more?infomation\n“
????????????program_name）;
????}else{
????????printf（“Usage:?%s??[FILE]?...\n“?program_name）;
????????printf（“with?no?FILE?or?when?FILE?is?-?%s?will?read?from?stdin\n“?program_name）;
????}

????exit（status）;
}

static?void
cat_exit（）
{
????exit（exit_status）;
}

static?void
_cat（int?fileno?int?needexit）
{
????char????????????????buf[MAX_BUF_SIZE];
????int?????????????????n;
????
????while（（n?=?read（fileno?buf?MAX_BUF_SIZE））?>?0）{
????????if（write（STDOUT_FILENO?buf?n）?!=?n）{
????????????perror（“in?write“）;
????????????exit（exit_status）;
????????}
????}

????if（n?????????perror（“in?read“）;
????????if（!needexit）
????????????exit（exit_status）;
????}

????if（needexit）{
????????exit_status?=?EXIT_SUCESS;
????????exit（exit_status）;
????}
}

static?void
simple_cat（char?*file）
{
????struct?stat?????????statbuf;
????
????if（file?==?NULL?||?file[0]?==?0）{
????????//sprintf（stderr?“some?asset?error?happend\n“）;
????????exit（exit_status）;
????}

????if（file[0]?==?‘-‘?&&?file[1]?==?0）/*從標準輸入讀數據*/
????????_cat（STDIN_FILENO?1）;???/*從標準輸入讀數據并顯示數據，然后退出*/

????/*下面是從file文件里面讀數據了*/
????input_desc?=?open（file?O_RDONLY）;
????if（input_desc?????????fprintf（stderr?“open?file?‘%s‘?error:?%s\n“?file?strerror（errno））;
????????exit（exit_status）;
????}

????if（fstat（input_desc?&statbuf）?????????fprintf（stderr?“fstat?file?‘%s‘?error:?%s\n“?file?strerror（errno））;
????????close（input_desc）;
????????exit（exit_status）;
????}

????if（S_ISREG（statbuf.st_mode）?==?0）{
????????fprintf（stderr?“file?‘%s‘?is?not?a?genel?file\n“?file）;
????????close（input_desc）;
????????exit（exit_status）;
????}

????_cat（input_desc?0）;
????close（input_desc）;
}

int
main（int?argc?char?*argv[]）
{
????struct?stat?????????stat_buf;
????int?????????????????c;
????static?struct?option?const?long_options[]?=
????{
????????{“help“?0?NULL?‘h‘}
????????????{NULL?0?NULL?0}
????};

????program_name?=?a

?屬性????????????大小?????日期????時間???名稱
-----------?---------??----------?-----??----

?????文件????????965??2014-06-25?13:37??my_linux_command\ReadMe.txt

????.......??????3899??2014-04-17?23:38??my_linux_command\cat.c

????.......??????4538??2014-05-30?11:55??my_linux_command\chattr.c

????.......??????2037??2014-05-16?16:37??my_linux_command\chgrp.c

????.......??????2299??2014-05-15?22:30??my_linux_command\chmod.c

????.......??????2053??2014-05-16?16:35??my_linux_command\chown.c

????.......??????2209??2014-05-09?21:30??my_linux_command\cp.c

????.......??????7807??2014-06-05?12:09??my_linux_command\cut.c

????.......??????6111??2014-05-16?13:37??my_linux_command\date.c

????.......??????2869??2014-06-05?12:08??my_linux_command\df.c

????.......??????1533??2014-06-05?12:08??my_linux_command\du.c

????.......???????636??2014-05-29?13:49??my_linux_command\echo.c

????.......??????2479??2014-06-17?09:56??my_linux_command\expand.c

????.......??????1869??2014-06-03?09:45??my_linux_command\find.c

????.......??????2131??2014-04-17?19:12??my_linux_command\getopt_long.c

????.......??????2857??2014-06-05?12:09??my_linux_command\grep.c

????.......??????4835??2014-05-09?10:37??my_linux_command\head.c

????.......??????7690??2014-06-17?09:56??my_linux_command\join.c

????.......??????4370??2014-06-05?12:08??my_linux_command\last.c

????.......???????268??2014-05-30?11:55??my_linux_command\lib\bit_opr.h

????.......??????2943??2014-06-17?09:56??my_linux_command\lib\char_map.h

????.......??????3019??2014-05-15?22:26??my_linux_command\lib\chmod.h

????.......??????3740??2014-05-16?16:35??my_linux_command\lib\chown.h

????.......???????513??2014-04-18?00:20??my_linux_command\lib\command_comm.h

????.......??????8973??2014-05-09?21:22??my_linux_command\lib\copy.h

????.......???????906??2014-06-17?09:56??my_linux_command\lib\err_msg.h

????.......??????1887??2014-05-13?21:53??my_linux_command\lib\file_isexist.h

????.......??????1868??2014-06-03?09:45??my_linux_command\lib\fileflag.h

????.......??????3328??2014-06-03?09:45??my_linux_command\lib\find_file.h

????.......??????2360??2014-06-17?09:56??my_linux_command\lib\get_filesize.h

............此處省略50個文件信息