awk实例

awk
FS：输入字段分隔符
OFS：输出字段分隔符
RS：输入时的换行符
ORS：输出的换行符
NF：字段数量
$NF:最后一个字段
NR：统计行数
FNR：各个文件的行数统计
FILENAME：当前处理的文件名路径
ARGC：命令行参数的个数
ARGV：数组，以ARGV($1,...)调用
1.[root@localhost ~]# awk -v FS=":" '{print $1}' /etc/passwd
[root@localhost ~]# awk  '{print $1}' /etc/passwd
[root@localhost ~]# gawk -v FS=":" '{print $1}' /etc/passwd相当于[root@localhost ~]# gawk -F: '{print $1}' /etc/passwd
[root@localhost ~]# awk -v FS=":" '{print $1,$3,$7}' /etc/passwd
[root@localhost ~]# awk -v FS=':' '{print $1,$3,$7}' /etc/passwd
[root@localhost ~]# awk -v FS=':' -v OFS='#' '{print $1,$3,$7}' /etc/passwd
[root@localhost ~]# awk -v RS=':' -v ORS='#' '{print}' /etc/passwd
root#x#0#0#root#/root#/bin/bash
bin#x#1#1#bin#/bin#/sbin/nologin
daemon#x#2#2#daemon#/sbin#/sbin/nologin
adm#x#3#4#adm#/var/adm#/sbin/nologin
lp#x#4#7#lp#/var/spool/lpd#/sbin/nologin

[root@localhost ~]# awk '{print NF}' /etc/fstab 统计行字段个数；

[root@localhost ~]# awk '{print $NF}' /etc/fstab cat /etc/fstab 显示最后一个字段

[root@localhost ~]# awk 'BEGIN{print ARGC}' /etc/fstab /etc/issue
3
[root@localhost ~]# awk 'BEGIN{print ARGV[0]}' /etc/fstab /etc/issue
awk
[root@localhost ~]# awk -v test='glq hello' '{print test,$1}' /etc/fstab 
glq hello 
glq hello #
glq hello #
glq hello #
[root@localhost ~]# awk 'BEGIN{test="welcome";print test,$2}' /etc/fstab 
welcome 
[root@localhost ~]# awk -v test='to my log' '{print test,$2}' /etc/fstab 
to my log 
to my log 
to my log /etc/fstab
to my log Created
to my log 
to my log Accessible
[root@localhost ~]# awk -F: -v test="my log" '{print test,$7}' /etc/passwd
my log /bin/bash
my log /sbin/nologin
my log /sbin/nologin

----------------------------

printf
[root@localhost ~]# awk -F: '{printf "username: %-15s,UID: %d
",$1,$3}' /etc/passwd
username: root           ,UID: 0
username: bin            ,UID: 1
username: daemon         ,UID: 2
username: adm            ,UID: 3
[root@localhost ~]# awk -F: '{printf "username: %-10s,UID: %-1d,   Shell: %s
",$1,$3,$7}' /etc/passwd
username: root      ,UID: 0,   Shell: /bin/bash
username: bin       ,UID: 1,   Shell: /sbin/nologin
username: daemon    ,UID: 2,   Shell: /sbin/nologin
[root@localhost ~]# awk -F: '{printf "username: %-10s UID: %-1d   Shell: %s
",$1,$3,$7}' /etc/passwd
username: root       UID: 0   Shell: /bin/bash
username: bin        UID: 1   Shell: /sbin/nologin
username: daemon     UID: 2   Shell: /sbin/nologin

if判断语句：
[root@localhost ~]# awk -F: '{$3>=1000?usertype="common user":usertype="system user";printf "%15s:%-s
",$1,usertype}' /etc/passwd
           root:system user
            bin:system user
         daemon:system user
            adm:system user
---------------------------------------
[root@localhost ~]# awk '/^UUID/{print $1}' /etc/fstab 
UUID=63539c8b-2d17-4c5e-aa11-e232515bba61
[root@localhost ~]# awk '!/^UUID/{print $1}' /etc/fstab 

#
#
#
#
#
#
#
/dev/mapper/centos-root
/dev/mapper/centos-swap
[root@localhost ~]# awk -F: '$3<1000{print "user:"$1,$3}' /etc/passwd
user:root 0
user:bin 1
user:daemon 2
user:adm 3
user:lp 4
user:sync 5
[root@localhost ~]# awk -F: '$NF=="/bin/bash"{print $1,$NF}' /etc/passwd
root /bin/bash
testdb /bin/bash
test1 /bin/bash
[root@localhost ~]# awk -F: '$NF~/bash$/{print $1,$NF}' /etc/passwd
root /bin/bash
testdb /bin/bash
test1 /bin/bash
[root@localhost ~]# awk -F: '/^root/,/^ftp/{print $1}' /etc/passwd
root
bin
daemon
adm
lp
sync
shutdown
halt
mail
operator
games
ftp
[root@localhost ~]# awk -F: '(NR>2&&NR<=10){print $1}' /etc/passwd
daemon
adm
lp
sync
shutdown
halt
mail
operator

BEGIN和END使用：
[root@localhost ~]# awk -F: 'BEGIN{print "username             UID 
------------------------"}{printf "%-21s %s
",$1,$3}' /etc/passwd
username             UID 
------------------------
root                  0
bin                   1
daemon                2
adm                   3
lp                    4
sync                  5
shutdown              6
halt                  7
mail                  8
operator              11
games                 12
ftp                   14
nobody                99
avahi-autoipd         170
systemd-bus-proxy     999
systemd-network       998
dbus                  81
polkitd               997
tss                   59
postfix               89
sshd                  74
mysql                 27
testdb                1000
test1                 1001
[root@localhost ~]# awk -F: 'BEGIN{print "username             UID 
------------------------"}{printf "%-21s %s
",$1,$3}END{print                  "end 
----------------------"}' /etc/passwd
username             UID 
------------------------
root                  0
bin                   1
daemon                2
adm                   3
lp                    4
sync                  5
shutdown              6
halt                  7
mail                  8
operator              11
games                 12
ftp                   14
nobody                99
avahi-autoipd         170
systemd-bus-proxy     999
systemd-network       998
dbus                  81
polkitd               997
tss                   59
postfix               89
sshd                  74
mysql                 27
testdb                1000
test1                 1001
end 
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