LINUX C中有关多个文件中宏的小问题

void mytool2_print(char *print_str)这是函数原型

#ifndef _MYTOOL_2_H

#define _MYTOOL_2_H

#endif

这是防止重复include， 实际上已经是个写头文件的“标准技巧”了。。

如果使用了多路径方案，可以直接使用multipath绑定设备名不需要用到asmlib或UDEV请直接参考文档：Configuringnon-rawmultipathdevicesforOracleClusterware11g(11.1.0,11.2.0)onRHEL5/OL5[ID605828.1][root@vrh1~]#foriin`cat/proc/partitions|awk'{print$4}'|grepsd|grep[a-z]$`doecho"###$i:`scsi_id-g-u-s/block/$i`"done###sda:SATA_VBOX_HARDDISK_VB83d4445f-b8790695_###sdb:SATA_VBOX_HARDDISK_VB0db2f233-269850e0_###sdc:SATA_VBOX_HARDDISK_VBa56f2571-0dd27b33_###sdd:SATA_VBOX_HARDDISK_VBf6b74ff7-871d1de8_###sde:SATA_VBOX_HARDDISK_VB5a531910-25f4eb9a_###sdf:SATA_VBOX_HARDDISK_VB4915e6e3-737b312e_###sdg:SATA_VBOX_HARDDISK_VB512c8f75-37f4a0e9_###sdh:SATA_VBOX_HARDDISK_VBc0115ef6-a48bc15d_###sdi:SATA_VBOX_HARDDISK_VB3a556907-2b72391d_###sdj:SATA_VBOX_HARDDISK_VB7ec8476c-08641bd4_###sdk:SATA_VBOX_HARDDISK_VB743e1567-d0009678_[root@vrh1~]#grep-v^#/etc/multipath.confdefaults{user_friendly_namesyes}defaults{udev_dir/devpolling_interval10selector"round-robin0"path_grouping_policyfailovergetuid_callout"/sbin/scsi_id-g-u-s/block/%n"prio_callout/bin/truepath_checkerreadsector0rr_min_io100rr_weightprioritiesfailbackimmediate#no_path_retryfailuser_friendly_nameyes}devnode_blacklist{devnode"^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*"devnode"^hd[a-z]"devnode"^cciss!c[0-9]d[0-9]*"}multipaths{multipath{wwidSATA_VBOX_HARDDISK_VB0db2f233-269850e0_aliasvoting1path_grouping_policyfailover}multipath{wwidSATA_VBOX_HARDDISK_VBa56f2571-0dd27b33_aliasvoting2path_grouping_policyfailover}multipath{wwidSATA_VBOX_HARDDISK_VBf6b74ff7-871d1de8_aliasvoting3path_grouping_policyfailover}multipath{wwidSATA_VBOX_HARDDISK_VB5a531910-25f4eb9a_aliasocr1path_grouping_policyfailover}multipath{wwidSATA_VBOX_HARDDISK_VB4915e6e3-737b312e_aliasocr2path_grouping_policyfailover}multipath{wwidSATA_VBOX_HARDDISK_VB512c8f75-37f4a0e9_aliasocr3path_grouping_policyfailover}}[root@vrh1~]#multipath[root@vrh1~]#multipath-llmpath2(SATA_VBOX_HARDDISK_VB3a556907-2b72391d_)dm-9ATA,VBOXHARDDISKsize=5.0Gfeatures='0'hwhandler='0'wp=rw`-+-policy='round-robin0'prio=1status=active`-8:0:0:0sdi8:128activereadyrunningmpath1(SATA_VBOX_HARDDISK_VBc0115ef6-a48bc15d_)dm-8ATA,VBOXHARDDISKsize=5.0Gfeatures='0'hwhandler='0'wp=rw`-+-policy='round-robin0'prio=1status=active`-7:0:0:0sdh8:112activereadyrunningocr3(SATA_VBOX_HARDDISK_VB512c8f75-37f4a0e9_)dm-7ATA,VBOXHARDDISKsize=5.0Gfeatures='0'hwhandler='0'wp=rw`-+-policy='round-robin0'prio=1status=active`-6:0:0:0sdg8:96activereadyrunningocr2(SATA_VBOX_HARDDISK_VB4915e6e3-737b312e_)dm-6ATA,VBOXHARDDISKsize=5.0Gfeatures='0'hwhandler='0'wp=rw`-+-policy='round-robin0'prio=1status=active`-5:0:0:0sdf8:80activereadyrunningocr1(SATA_VBOX_HARDDISK_VB5a531910-25f4eb9a_)dm-5ATA,VBOXHARDDISKsize=5.0Gfeatures='0'hwhandler='0'wp=rw`-+-policy='round-robin0'prio=1status=active`-4:0:0:0sde8:64activereadyrunningvoting3(SATA_VBOX_HARDDISK_VBf6b74ff7-871d1de8_)dm-4ATA,VBOXHARDDISKsize=40Gfeatures='0'hwhandler='0'wp=rw`-+-policy='round-robin0'prio=1status=active`-3:0:0:0sdd8:48activereadyrunningvoting2(SATA_VBOX_HARDDISK_VBa56f2571-0dd27b33_)dm-3ATA,VBOXHARDDISKsize=40Gfeatures='0'hwhandler='0'wp=rw`-+-policy='round-robin0'prio=1status=active`-2:0:0:0sdc8:32activereadyrunningvoting1(SATA_VBOX_HARDDISK_VB0db2f233-269850e0_)dm-2ATA,VBOXHARDDISKsize=40Gfeatures='0'hwhandler='0'wp=rw`-+-policy='round-robin0'prio=1status=active`-1:0:0:0sdb8:16activereadyrunningmpath4(SATA_VBOX_HARDDISK_VB743e1567-d0009678_)dm-11ATA,VBOXHARDDISKsize=5.0Gfeatures='0'hwhandler='0'wp=rw`-+-policy='round-robin0'prio=1status=active`-10:0:0:0sdk8:160activereadyrunningmpath3(SATA_VBOX_HARDDISK_VB7ec8476c-08641bd4_)dm-10ATA,VBOXHARDDISKsize=5.0Gfeatures='0'hwhandler='0'wp=rw`-+-policy='round-robin0'prio=1status=active`-9:0:0:0sdj8:144activereadyrunning[root@vrh1~]#dmsetupls|sortmpath1(253,8)mpath2(253,9)mpath3(253,10)mpath4(253,11)ocr1(253,5)ocr2(253,6)ocr3(253,7)VolGroup00-LogVol00(253,0)VolGroup00-LogVol01(253,1)voting1(253,2)voting2(253,3)voting3(253,4)[root@vrh1~]#ls-l/dev/mapper/*crw-------1rootroot10,62Oct1709:58/dev/mapper/controlbrw-rw----1rootdisk253,8Oct1900:11/dev/mapper/mpath1brw-rw----1rootdisk253,9Oct1900:11/dev/mapper/mpath2brw-rw----1rootdisk253,10Oct1900:11/dev/mapper/mpath3brw-rw----1rootdisk253,11Oct1900:11/dev/mapper/mpath4brw-rw----1rootdisk253,5Oct1900:11/dev/mapper/ocr1brw-rw----1rootdisk253,6Oct1900:11/dev/mapper/ocr2brw-rw----1rootdisk253,7Oct1900:11/dev/mapper/ocr3brw-rw----1rootdisk253,0Oct1709:58/dev/mapper/VolGroup00-LogVol00brw-rw----1rootdisk253,1Oct1709:58/dev/mapper/VolGroup00-LogVol01brw-rw----1rootdisk253,2Oct1900:11/dev/mapper/voting1brw-rw----1rootdisk253,3Oct1900:11/dev/mapper/voting2brw-rw----1rootdisk253,4Oct1900:11/dev/mapper/voting3[root@vrh1~]#ls-l/dev/dm*brw-rw----1rootroot253,0Oct1709:58/dev/dm-0brw-rw----1rootroot253,1Oct1709:58/dev/dm-1brw-rw----1rootroot253,10Oct1900:11/dev/dm-10brw-rw----1rootroot253,11Oct1900:11/dev/dm-11brw-rw----1rootroot253,2Oct1900:11/dev/dm-2brw-rw----1rootroot253,3Oct1900:11/dev/dm-3brw-rw----1rootroot253,4Oct1900:11/dev/dm-4brw-rw----1rootroot253,5Oct1900:11/dev/dm-5brw-rw----1rootroot253,6Oct1900:11/dev/dm-6brw-rw----1rootroot253,7Oct1900:11/dev/dm-7brw-rw----1rootroot253,8Oct1900:11/dev/dm-8brw-rw----1rootroot253,9Oct1900:11/dev/dm-9[root@vrh1~]#ls-l/dev/disk/by-id/total0lrwxrwxrwx1rootroot15Oct1709:58scsi-SATA_VBOX_HARDDISK_VB0db2f233-269850e0->../../asm-diskblrwxrwxrwx1rootroot15Oct1709:58scsi-SATA_VBOX_HARDDISK_VB3a556907-2b72391d->../../asm-diskilrwxrwxrwx1rootroot15Oct1709:58scsi-SATA_VBOX_HARDDISK_VB4915e6e3-737b312e->../../asm-diskflrwxrwxrwx1rootroot15Oct1709:58scsi-SATA_VBOX_HARDDISK_VB512c8f75-37f4a0e9->../../asm-diskglrwxrwxrwx1rootroot15Oct1709:58scsi-SATA_VBOX_HARDDISK_VB5a531910-25f4eb9a->../../asm-diskelrwxrwxrwx1rootroot15Oct1709:58scsi-SATA_VBOX_HARDDISK_VB743e1567-d0009678->../../asm-diskklrwxrwxrwx1rootroot15Oct1709:58scsi-SATA_VBOX_HARDDISK_VB7ec8476c-08641bd4->../../asm-diskjlrwxrwxrwx1rootroot9Oct1709:58scsi-SATA_VBOX_HARDDISK_VB83d4445f-b8790695->../../sdalrwxrwxrwx1rootroot10Oct1709:58scsi-SATA_VBOX_HARDDISK_VB83d4445f-b8790695-part1->../../sda1lrwxrwxrwx1rootroot10Oct1709:58scsi-SATA_VBOX_HARDDISK_VB83d4445f-b8790695-part2->../../sda2lrwxrwxrwx1rootroot15Oct1709:58scsi-SATA_VBOX_HARDDISK_VBa56f2571-0dd27b33->../../asm-diskclrwxrwxrwx1rootroot15Oct1709:58scsi-SATA_VBOX_HARDDISK_VBc0115ef6-a48bc15d->../../asm-diskhlrwxrwxrwx1rootroot15Oct1709:58scsi-SATA_VBOX_HARDDISK_VBf6b74ff7-871d1de8->../../asm-diskdReportAbuseLike(0)2.Re:asm磁盘使用链路聚合设备名，IO性能只有非聚合设备的1/6!LiuMaclean(刘相兵)ExpertLiuMaclean(刘相兵)Jul21,201311:09AM(inresponseto13628)step1:[oracle@vrh8mapper]$cat/etc/multipath.confmultipaths{multipath{wwidSATA_VBOX_HARDDISK_VBf6b74ff7-871d1de8_aliasasm-disk1mode660uid501gid503}multipath{wwidSATA_VBOX_HARDDISK_VB0db2f233-269850e0_aliasasm-disk2mode660uid501gid503}multipath{wwidSATA_VBOX_HARDDISK_VBa56f2571-0dd27b33_aliasasm-disk3mode660uid501gid503}}第二步：rebootorservicemultipathdrestart第三步：[oracle@vrh8mapper]$ls-l/dev/mapper/asm-disk*brw-rw----1gridasmadmin253,4Jul2107:02/dev/mapper/asm-disk1brw-rw----1gridasmadmin253,2Jul2107:02/dev/mapper/asm-disk2brw-rw----1gridasmadmin253,3Jul2107:02/dev/mapper/asm-disk3

open 函数可以打开或创建一个文件。

#include <sys/types.h>

#include <sys/stat.h>

#include <fcntl.h>

int open(const char *pathname, int flags)

int open(const char *pathname, int flags, mode_t mode)

返回值:成功返回新分配的文件描述符,出错返回-1并设置errno

在Man Page中open 函数有两种形式,一种带两个参数,一种带三个参数,其实在C代码

中open 函数是这样声明的:

int open(const char *pathname, int flags, ...)

最后的可变参数可以是0个或1个,由flags 参数中的标志位决定,见下面的详细说明。

pathname 参数是要打开或创建的文件名,和fopen 一样,pathname 既可以是相对路径也可以是绝

对路径。flags 参数有一系列常数值可供选择,可以同时选择多个常数用按位或运算符连接起

来,所以这些常数的宏定义都以O_开头,表示or。

必选项:以下三个常数中必须指定一个,且仅允许指定一个。

O_RDONLY 只读打开

O_WRONLY 只写打开

O_RDWR 可读可写打开

以下可选项可以同时指定0个或多个,和必选项按位或起来作为flags 参数。可选项有很多,这

里只介绍一部分,其它选项可参考open(2)的Man Page:

O_APPEND 表示追加。如果文件已有内容,这次打开文件所写的数据附加到文件的末尾而不

覆盖原来的内容。

O_CREAT 若此文件不存在则创建它。使用此选项时需要提供第三个参数mode ,表示该文件

的访问权限。

O_EXCL 如果同时指定了O_CREAT,并且文件已存在,则出错返回。

O_TRUNC 如果文件已存在,并且以只写或可读可写方式打开,则将其长度截断

(Truncate)为0字节。

O_NONBLOCK 对于设备文件,以O_NONBLOCK 方式打开可以做非阻塞I/O(Nonblock I/O).

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