/*
?* 有親緣關(guān)系的進(jìn)程間的fifo的使用
?* fifo 使用的簡單例子
?*/

#include?"../all.h"

#define?FIFO_PATH?"/tmp/hover_fifo"


void?
do_sig(int?signo)
{
????if?(signo?==?SIGCHLD)
????????while?(waitpid(-1,?NULL,?WNOHANG)?>?0)
????????????;
}

int
main(void)
{
????int?ret;
????int?fdr,?fdw;
????pid_t?pid;

????char?words[10]?=?"123456789";
????char?buf[10]?=?{'\0'};????
????
????// 創(chuàng)建它,若存在則不算是錯(cuò)誤,
????// 若想修改其屬性需要先打開得到fd,然后用fcntl來獲取屬性,然后設(shè)置屬性.

????if?(((ret?=?mkfifo(FIFO_PATH,?FILE_MODE))?==?-1)?

???????????????????? &&?(errno?!=?EEXIST))
????????perr_exit("mkfifo()");
????fprintf(stderr,?"fifo : %s created successfully!\n",?FIFO_PATH);

????signal(SIGCHLD,?do_sig);

????pid?=?fork();
????if?(pid?==?0)?{?// child

????????if?((fdr?=?open(FIFO_PATH,?O_WRONLY))?<?0)?// 打開fifo用來寫
????????????perr_exit("open()");
????????sleep(2);

??????? // 寫入數(shù)據(jù)
????????if?(write(fdr,?words,?sizeof(words))?!=?sizeof(words))?
????????????perr_exit("write");
????????fprintf(stderr,?"child write : %s\n",?words);
????????close(fdw);
????}?else?if?(pid?>?0)?{?// parent

????????if?((fdr?=?open(FIFO_PATH,?O_RDONLY))?<?0)?// 打開fifo用來讀

????????????perr_exit("open()");

????????fprintf(stderr,?"I father read, waiting for child ...\n");
????????if?(read(fdr,?buf,?9)?!=?9)?//讀數(shù)據(jù)
????????????perr_exit("read");

????????fprintf(stderr,?"father get buf : %s\n",?buf);
????????close(fdr);
????}
????// 到這里fifo管道并沒有被刪除,必須手動(dòng)調(diào)用函數(shù)unlink或remove刪除.

????return?0;????
}
?

/*
?* FIFO server
?*/

#include?"all.h"

int
main(void)
{
????int?fdw,?fdw2;
????int?fdr;
????char?clt_path[PATH_LEN]?=?{'\0'};
????char?buf[MAX_LINE]?=?{'\0'};
????char?*p;
????int?n;
????
????if?(mkfifo(FIFO_SVR,?FILE_MODE)?==?-1?&&?errno?!=?EEXIST)????
????????perr_exit("mkfifo()");????
????if?((fdr?=?open(FIFO_SVR,?O_RDONLY))?<?0)????
????????perr_exit("open()");
????/*?
???? * 根據(jù)fifo的創(chuàng)建規(guī)則, 若從一個(gè)空管道或fifo讀,?

???? * 而在讀之前管道或fifo有打開來寫的操作, 那么讀操作將會(huì)阻塞?
???? * 直到管道或fifo不打開來讀, 或管道或fifo中有數(shù)據(jù)為止.?

???? *

???? * 這里,我們的fifo本來是打開用來讀的,但是為了,read不返回0,

???? * 讓每次client端讀完都阻塞在fifo上,我們又打開一次來讀.
???? * 見unpv2 charper 4.7
???? */
????if?((fdw2?=?open(FIFO_SVR,?O_WRONLY))?<?0)????
????????fprintf(stderr,?"open()");
????
????while?(1)?{
????????/* read client fifo path from FIFO_SVR */

???? /* 這里由于FIFO_SVR有打開來寫的操作,所以當(dāng)管道沒有數(shù)據(jù)時(shí),?

????? * read會(huì)阻塞,而不是返回0.?

????? */
????????if?(read(fdr,?clt_path,?PATH_LEN)?<?0)?{
????????????fprintf(stderr,?"read fifo client path error : %s\n",?strerror(errno));????
????????????break;
????????}
????????if?((p?=?strstr(clt_path,?"\r\n"))?==?NULL)?{
????????????fprintf(stderr,?"clt_path error: %s\n",?clt_path);
????????????break;
????????}
????????*p?=?'\0';
????????DBG("clt_path",?clt_path);
????????if?(access(clt_path,?W_OK)?==?-1)?{?// client fifo ok, but no permission

????????????perror("access()");????
????????????continue;
????????}
????????/* open client fifo for write */
????????if?((fdw?=?open(clt_path,?O_WRONLY))?<?0)?{
????????????perror("open()");????
????????????continue;
????????}
????????if?((n?=?read(fdr,?buf,?WORDS_LEN))?>?0)?{?/* read server words is ok */
????????????printf("server read words : %s\n",?buf);
????????????buf[n]?=?'\0';
????????????write(fdw,?buf,?strlen(buf));????
????????}
????}
????
????close(fdw);????
????unlink(FIFO_SVR);
????exit(0);
}

/*
?* Fifo client
?*
?*/
#include?"all.h"



int
main(void)
{
????int?fdr,?fdw;
????pid_t?pid;????
????char?clt_path[PATH_LEN]?=?{'\0'};
????char?buf[MAX_LINE]?=?{'\0'};
????char?buf_path[MAX_LINE]?=?{'\0'};
????
????snprintf(clt_path,?PATH_LEN,?FIFO_CLT_FMT,?(long)getpid());????????
????DBG("clt_path1 = ",?clt_path);
????snprintf(buf_path,?PATH_LEN,?"%s\r\n",?clt_path);

????if?(mkfifo(clt_path,?FILE_MODE)?==?-1?&&?errno?!=?EEXIST)????
????????perr_exit("mkfifo()");

????/* client open clt_path for read
???? * open server for write?
?????? */
????if?((fdw?=?open(FIFO_SVR,?O_WRONLY))?<?0)?
????????perr_exit("open()");
????
????/* write my fifo path to server */????
????if?(write(fdw,?buf_path,?PATH_LEN)?!=?PATH_LEN)????????
????????perr_exit("write()");
????if?(write(fdw,?WORDS,?WORDS_LEN)?<?0)????/* write words to fifo server */
????????perr_exit("error");

????if?((fdr?=?open(clt_path,?O_RDONLY))?<?0)????
????????perr_exit("open()");
????if?(read(fdr,?buf,?WORDS_LEN)?>?0)?{?????/* read reply from fifo server */
????????buf[WORDS_LEN]?=?'\0';
????????printf("server said : %s\n",?buf);
????}
????
????close(fdr);
????unlink(clt_path);
????
????exit(0);
}