[20180131]bash變數替換與擷取.txt

[20180131]bash變數替換與擷取.txt

--//bash程式設計經常用到變數替換與擷取,經常記不住,做一些例子說明:

$ a=1a1b1c1d
$ echo $a
1a1b1c1d

$ echo ${a##*1}
d

$ echo ${a#*1}
a1b1c1d

--// ## 最長匹配替換  #  最短匹配替換

$ echo ${a%1*}
1a1b1c
$ echo ${a%%1*}

$ echo ${a%%c*}
1a1b1

--//  %% 表示從尾部開始最長匹配替換 % 表示從尾部開始最短匹配替換

$ echo ${a/1/|}
|a1b1c1d

$ echo ${a//1/|}
|a|b|c|d

--//  /替換1次  //全域性替換  注意後面沒有斜線.

$ echo -e ${PATH//:/\\n}
/u01/app/oracle/product/11.2.0.4/dbhome_1/jdk/bin
/usr/bin
/u01/app/oracle/product/11.2.0.4/dbhome_1/jdk/bin
/usr/bin
/usr/kerberos/bin
/usr/local/bin
/bin
/usr/bin
/usr/NX/bin
/home/oracle/bin
/u01/app/oracle/product/11.2.0.4/dbhome_1/bin
/home/oracle/anysql
/usr/NX/bin
/home/oracle/bin
/u01/app/oracle/product/11.2.0.4/dbhome_1/bin
/home/oracle/anysql

--//實際上bash還有許多功能,這些實際平時不用,實在記不住...