awk 常用函數的事~

awk一些函數+簡單示例，沒有概念，實踐中記憶：

1.split //split(域名，數組，分隔符）
[root@localhost ~]# cat a
abc abd abe abf abg
[root@localhost ~]# awk '{split($0,a," "); print length(a);for(i in a) print a[i]}' a //$0按空格作爲分隔符，順序存入數組a中
5
abf
abg
abc
abd
abe
2.sub //替換函數，sub(舊字符串，新字符串，作用域）
[root@localhost ~]# echo abc abc abc abc | awk '{sub("c","k",$4); print }'  //把第4個作用域的c替換爲k
abc abc abc abk
[root@localhost ~]# echo abc abc abc abc | awk '{sub("c","k"); print }'     //沒寫作用域，默認匹配第一次
abk abc abc abc
3.gsub //相比sub，多了global參數
[root@localhost ~]# echo abc abc abc abc | awk '{gsub("c","k"); print }'
abk abk abk abk
[root@localhost ~]# echo abc abc abc abc | awk '{gsub("c","k",$4); print }'
abc abc abc abk


4.index //index(作用域，字符串)
[root@localhost ~]# echo abc ack | awk '{if(index($1,"k")) print "yes";else print "no"; }'
no
[root@localhost ~]# echo abc ack | awk '{if(index($2,"k")) print "yes";else print "no"; }'
yes
[root@localhost ~]# echo abc ack | awk '{print index($2,"k")}' //查到匹配字符串位置
3
5.length(s) //打印字符串長度
[root@localhost ~]# echo abcdefg hijkl | awk '{ print length($0) }'
13

6.match //match（作用域，字符串) 跟index類似
[root@localhost ~]# echo abc abk | awk '{ print match($2,"k") }'
3
[root@localhost ~]# echo abc abk | awk '{ print match($1,"k") }'
0

7.substr //截取字符串，substr（作用域，開始位置，結束位置)
[root@localhost ~]# echo abc abchelloworld | awk '{b=substr($2,4); print b}'   //沒有結束位置，默認到結尾
helloworld
[root@localhost ~]# echo abc abchelloworld | awk '{b=substr($2,4,5); print b}' //第4個字符開始取出5個字符
hello
6.tolower(s)  //字符串轉換爲小寫
[root@localhost ~]# echo ABC ABC ABC | awk '{print tolower($0)}'
abc abc abc
[root@localhost ~]# echo ABC ABC ABC | awk '{b=tolower($2); print b}'
abc
7.toupper(s)  //字符串轉換爲大寫
[root@localhost ~]# echo abc abc abc | awk '{print toupper($0)}'
ABC ABC ABC
[root@localhost ~]# echo abc abc abc | awk '{b=toupper($2); print b}'
ABC
8.system()   //執行系統命令
[root@localhost ~]# awk 'BEGIN{ print system("ls -a") }'
.        .bash_logout   .dmrc       .gnome         .ICEauthority       .mysql_history  .Trash
..       .bash_profile  .eggcups    .gnome2        install.log     .nautilus       .viminfo
a        .bashrc    .evolution  .gnome2_private    install.log.syslog  .redhat     .Xauthority
anaconda-ks.cfg  .cshrc     .gconf      .gstreamer-0.10    .metacity       .tcshrc
.bash_history    Desktop    .gconfd     .gtkrc-1.2-gnome2  .mozilla        .thumbnails
0
9.gensub()  //gensub(舊字符串，新字符串，替換位置，作用域）
[root@localhost ~]# echo abaa adaa aaaa | awk '{b=gensub("a","k",3,$3); print b}'
aaka
[root@localhost ~]# echo abaa adaa aaaa | awk '{b=gensub("a","k",4,$3); print b}'
aaak

10.strftime()  //時間函數
[root@localhost ~]# awk 'BEGIN{ now=strftime("%y-%m-%d %H-%M-%S"); print now}'
13-01-12 21-14-30

getline   //獲取下一行，以下幾種常用用法
[root@localhost ~]# echo -e "abc\nabd\nabe" > a
[root@localhost ~]# awk 'BEGIN{ getline < "a"; print }'
abc
[root@localhost ~]# awk '/abc/{ getline tmp; print tmp; print }' a  //當前行和下一行對調
abd
abc
[root@localhost ~]# awk 'BEGIN { getline < "-"; print }'  //打印鍵盤輸入的內容
hello
hello
[root@localhost ~]# awk '{ getline line < "a"; print line }' a   //打印出文件內容
abc
abd
abe
[root@localhost ~]# seq 10 | awk '{getline; print}'  //注與BEGIN的區別，此處awk指針有跳轉
2
4
6
8
10
[root@localhost ~]# seq 10 | awk 'BEGIN{while(getline)print}' //此處awk指針沒有跳轉
1
2
3
4
5
6
7
8
9
10

next  //結束當前行，讀取下一行，並從從頭執行命令
[root@localhost ~]# cat a
abc
abd
abe
[root@localhost ~]# awk '/abc/{print "yes"; next;}{ print "no"}' a
yes
no
no


exit //退出執行
[root@localhost ~]# echo -e "a\na\na\na\na\na\nb\na\na" | awk '/b/{exit;}{print "yes"}'
yes
yes
yes
yes
yes
yes