awk使用备忘

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awk的主体块

主体部分的语法要求如下：

/pattern/ {awk-commands}

前段时间有个需求：就是获取db2 list directory的结果中与我的需求数据库名称一致的数据库的一些信息：

[db2inst1@bogon tmp]$ db2 list db directory System Database Directory Number of entries in the directory = 3Database 1 entry: Database alias                       = DBMDB Database name                        = DBMDB Local database directory             = /home/db2inst1 Database release level               = 14.00 Comment                              = Directory entry type                 = Indirect Catalog database partition number    = 0 Alternate server hostname            = Alternate server port number         =Database 2 entry: Database alias                       = TYDB_161 Database name                        = TYDB Node name                            = NODE_161 Database release level               = 14.00 Comment                              = Directory entry type                 = Remote Catalog database partition number    = -1 Alternate server hostname            = Alternate server port number         =Database 3 entry: Database alias                       = MYDB Database name                        = MYDB Local database directory             = /home/db2inst1 Database release level               = 14.00 Comment                              = Directory entry type                 = Indirect Catalog database partition number    = 0 Alternate server hostname            = Alternate server port number         =

比方说想获得Database alias= MYDB的其他信息，比如Database name，Local Database directory信息等，当时的处理办法是这样的：

[db2inst1@bogon tmp]$ db2 list db directory| grep 'MYDB' -A 5|grep 'Database name'|awk -F'=' '{print $2}' MYDB[db2inst1@bogon tmp]$ db2 list db directory| grep 'MYDB' -A 5|grep 'Local database directory'|awk -F'=' '{print $2}' /home/db2inst1

grep了两次，还是有点儿繁琐的哈，后面看到了“别人家的”代码是这样处理的：

亮点在这里哦：

DBName=$(db2 list db directory|awk -v dba='MYDB' '/^ Database alias[ ]*=/{if(dba==$NF){flag=1}}/^ Database name[ ]*=/{if(flag==1){printf "%s",$NF;exit}}')DBPath=$(db2 list db directory|awk -v dba='MYDB' '/^ Database alias[ ]*=/{if(dba==$NF){flag=1}}/^ Local database directory[ ]*=/{if(flag==1){printf "%s",$NF;exit}}')

awk的主体块（Body Block）
主体部分的语法要求如下：

/pattern/ {awk-commands}

对于每一个输入的行都会执行一次主体部分的命令。默认情况下，对于输入的每一行，AWK 都会很执行命令。但是，我们可以将其限定在指定的模式中。注意，在主体块部分没有关键字存在。
所以上面的示例，当匹配到以‘ Database alias’开头的行后，判断他最后一个域是否等于MYDB，如果等于的话，flag设置为1；然后继续匹配下面的行，匹配到‘Database name’开头的行后，判断flag等于1的话，就输出，因为可能下面还会继续匹配到‘ Database name’开头的行，但我们只需要紧相邻的行，所以要记得print完了之后exit。

进阶：

需求：就是我需要检查db2dart导出的文件的column的顺序，获取Column 1：之后的这行Value，然后输出所有的Value。
Record Type= Table Data Record

            Slot 3:               Offset Location = 2868  (xB34)               Record Length = 48  (x30)               Record Type = Table Description Record                  Number of Columns = 5                  Column 1:                  Type is Long Integer                  Length = 4                  Prohibits NULLs                  Prohibits Default            Fixed offset: 0                  Column 2:                  Type is Variable Length Character String                  Maximum Length = 20                  Allows NULLs                  Prohibits Default            Fixed offset: 4          Fixed offset: 4                  Column 3:                  Type is Small Integer                  Length = 2                  Allows NULLs                  Prohibits Default            Fixed offset: 9                  Column 4:                  Type is Variable Length Character String                  Maximum Length = 200                  Allows NULLs                  Prohibits Default            Fixed offset: 12                  Column 5:                  Type is Fixed Length Character String                  Length = 4                  Allows NULLs                  Prohibits Default            Fixed offset: 17            Slot 4:               Offset Location = 2742  (xAB6)               Offset Location = 2742  (xAB6)               Record Length = 126  (x7E)               Record Type = Table Data Record (FIXEDVAR) (PUNC)               Record Flags = 0               Fixed part length value = 22                  Column 1:            Fixed offset: 0                  Type is Long Integer                  Value = 3001                  Column 2:            Fixed offset: 4                  Type is Variable Length Character String                  Length = 6 Offset = 22                      74344C54 5434                          t4LTT4                            Column 3:            Fixed offset: 9                  Type is Small Integer                  Value = 0                  Column 4:            Fixed offset: 12                  Type is Variable Length Character String                  Length = 90 Offset = 28                      54347434 54347434 54347434 54347434    T4t4T4t4T4t4T4t4                54347434 54347434 54347434 74347434    T4t4T4t4T4t4t4t4                74347434 74347434 74346173 6466736B    t4t4t4t4t4asdfsk                64666166 61736673 66736466 61736466    dfafasfsfsdfasdf                6A736164 666C6120 73207366 64617364    jsadfla s sfdasd                66736466 61647366 6173                 fsdfadsfas                        Column 5:            Fixed offset: 17                  Type is Fixed Length Character String                      62656E6B                               benk                        Slot 5:

上面是文件的部分示例，现在就是要取出这个文件中我们需要的部分。

awk使用案例

示例1：

$(echo "${_output}"|tail -1|awk '{if($1~"^[-,0-9]*$"){printf "%d",$1}else{printf "%d",5}}')

[db2inst1@bogon tmp]$ db2 "force application all"DB20000I  The FORCE APPLICATION command completed successfully.DB21024I  This command is asynchronous and may not be effective immediately.

示例2

[db2inst1@bogon tmp]$ echo '-1316,-1017'|awk -F, -v c='-1316' '{for(i=1;i<=NF;i++){if($i==c && c!=0){f=1}}}END{if(f==1){printf 100}else{printf "%d",c}}' 100

这个代码不好看懂的话我们整理格式化一下：

awk -F, -v c='-1316' '{for(i=1;i<=NF;i++)  {if($i==c && c!=0)    {f=1}  }}END{if(f==1)       {printf 100}    else       {printf "%d",c}   }'

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