Regular Introduction_awk

9.6/9.7 awk

awk tools

It has more functions than grep and sed tools and can be operated in segments.

• Segment operation

# - F specifies the delimiter, defaulting to space {}Internal # $1 means: the first field after segmentation # $0 represents a line # First paragraph of printed content [root@centos7 tmp]# head test.txt | awk -F ':' '{ print $1}' root bin daemon adm lp sync shutdown halt mail operator # Print entire line [root@localhost ~]# head test.txt | awk -F ":" '' 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 sync:x:5:0:sync:/sbin:/bin/sync shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown halt:x:7:0:halt:/sbin:/sbin/halt mail:x:8:12:mail:/var/spool/mail:/sbin/nologin operator:x:11:0:operator:/root:/sbin/nologin

• Matching for segments

# + Matching Content (no need to add\ escape) [root@centos7 tmp]# head test.txt | awk -F ':' '$1 ~ /root/' root:x:0:0:root:/root:/bin/bash

• Matching multiple conditions

[root@centos7 tmp]# awk -F ':' '/root/ /mail/ ' test.txt root 0 mail 8 12 operator 11 # Specify a delimiter and print out in the same format [root@centos7 tmp]# awk -F ':' '/root|mail/ ' test.txt root 0 mail 8 operator 11 # Specify the delimiter, print out in different formats, and specify the output delimiter [root@localhost ~]# awk -F ':' '/root/ /mail/ ' /etc/passwd root # 0 mail # 8 # 12 operator # 11

• Conditional judgement

Double quotation marks are needed for string conditions, which are sorted in string order; double quotation marks are not needed for numeric order. Available conditional judgement symbols include: >= <====!=.

# Single Field Conditional Judgment [root@centos7 tmp]# awk -F ':' '$3>=1000' test.txt castiel:x:1000:1000::/home/castiel:/bin/bash [root@centos7 tmp]# awk -F ':' '$3>=1000 ' test.txt castiel # === Equality (field comparison) [root@centos7 tmp]# awk -F ':' '$3==$4' test.txt root:x:0:0:root:/root:/bin/bash bin:x:1:1:bin:/bin:/sbin/nologin daemon:x:2:2:daemon:/sbin:/sbin/nologin nobody:x:99:99:Nobody:/:/sbin/nologin systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin dbus:x:81:81:System message bus:/:/sbin/nologin tss:x:59:59:Account used by the trousers package to sandbox the tcsd daemon:/dev/null:/sbin/nologin postfix:x:89:89::/var/spool/postfix:/sbin/nologin sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin castiel:x:1000:1000::/home/castiel:/bin/bash # = = not equal to [root@localhost ~]# awk -F ':' '$7!="/sbin/nologin" ' test.txt root sync shutdown halt castiel # Use & or | to achieve multi-conditional judgment [root@localhost ~]# awk -F ':' '$7!="/sbin/nologin" && $3==$4' /etc/passwd root:x:0:0:root:/root:/bin/bash mysql:x:1000:1000::/home/mysql:/bin/bash

• Use conditional statements

[root@centos7 tmp]# awk -F ':' '}' test.txt castiel#1000#1000

# OFS represents the output separator [root@centos7 tmp]# head test.txt |awk -F ':' ' ' root#0#0 bin#1#1 daemon#2#2 adm#3#4 lp#4#7 sync#5#0 shutdown#6#0 halt#7#0 mail#8#12 operator#11#0 # NR: Number of rows, using $NR corresponds to $1, $2... [root@centos7 tmp]# awk -F ':' '' test.txt | head 1 root:x:0:0:root:/root:/bin/bash 2 bin:x:1:1:bin:/bin:/sbin/nologin 3 daemon:x:2:2:daemon:/sbin:/sbin/nologin 4 adm:x:3:4:adm:/var/adm:/sbin/nologin 5 lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin 6 sync:x:5:0:sync:/sbin:/bin/sync 7 shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown 8 halt:x:7:0:halt:/sbin:/sbin/halt 9 mail:x:8:12:mail:/var/spool/mail:/sbin/nologin 10 operator:x:11:0:operator:/root:/sbin/nologin # NF denotes the number of segments per line, where the value of NF is 7, so $NF is equivalent to $7. [root@localhost ~]# awk -F ':' '' test.txt | head 1 /bin/bash 2 /sbin/nologin 3 /sbin/nologin 4 /sbin/nologin 5 /sbin/nologin 6 /bin/sync 7 /sbin/shutdown 8 /sbin/halt 9 /sbin/nologin 10 /sbin/nologin

• Assignment: Use =, unlike ==, its output will have no delimiter, which needs to be specified using OFS

[root@centos7 tmp]# head -n 3 test.txt | awk -F ':' ' $1="root"' root:x:0:0:root:/root:/bin/bash root:x:1:1:bin:/bin:/sbin/nologin root:x:2:2:daemon:/sbin:/sbin/nologin

# Calculate the sum of the numbers in the third paragraph [root@localhost ~]# awk -F ':' '{(tot=tot+$3)}; END ' test.txt 4661

31 January 2019, 05:03 | Views: 4127