awk practice questions
Test original file content:
[root@lgs-01 awk]# cat test
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
games:x:12:100:games:/usr/games:/sbin/nologin
ftp:x:14:50:FTP User:/var/ftp:/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
polkitd:x:999:997:User for polkitd:/:/sbin/nologin
postfix:x:89:89::/var/spool/postfix:/sbin/nologin
sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin
chrony:x:998:996::/var/lib/chrony:/sbin/nologin
lgs:x:1008:1000::/home/lgs:/bin/bash
abc:x:1001:1000::/home/abc:/bin/bash
12:22:55
587:1
12:21
2:2:1:fsfs:root:/bin/:/user
342:x:3d:fafa:toor:/user:/bin
xx:xx:xx:xx:xx:xx:34
rr:rr:rr:rr:rr:rr:t55abc
##:#34#:bb:bb:bb:%pp^:$!#
#234#:vv:vv:vv:vv:ds:@user#
1. Use awk to print the entire test (the following operations are implemented with awk tools, for test)
答案：awk -F ':' '{print $0}' test
[root@lgs-01 awk]# awk -F ':' '{print $0}' test
root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/bin:/sbin/nologin
daemon:x:2:2:daemon:/sbin:/sbin/nologin
adm:x:3:4:adm:/var/adm:/sbin/nologin
lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
sync:x:5:0:sync:/sbin:/bin/sync
shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
halt:x:7:0:halt:/sbin:/sbin/halt
mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
operator:x:11:0:operator:/root:/sbin/nologin
games:x:12:100:games:/usr/games:/sbin/nologin
ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin
nobody:x:99:99:Nobody:/:/sbin/nologin
systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin
dbus:x:81:81:System message bus:/:/sbin/nologin
polkitd:x:999:997:User for polkitd:/:/sbin/nologin
postfix:x:89:89::/var/spool/postfix:/sbin/nologin
sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin
chrony:x:998:996::/var/lib/chrony:/sbin/nologin
lgs:x:1008:1000::/home/lgs:/bin/bash
abc:x:1001:1000::/home/abc:/bin/bash
12:22:55
587:1
12:21
2:2:1:fsfs:root:/bin/:/user
342:x:3d:fafa:toor:/user:/bin
xx:xx:xx:xx:xx:xx:34
rr:rr:rr:rr:rr:rr:t55abc
##:#34#:bb:bb:bb:%pp^:$!#
#234#:vv:vv:vv:vv:ds:@user#
2. Find all lines containing 'bash'
答案：awk -F ':' '$0 ~ /bash/' test
[root@lgs-01 awk]# awk -F ':' '$0 ~ /bash/' test
root:x:0:0:root:/root:/bin/bash
lgs:x:1008:1000::/home/lgs:/bin/bash
abc:x:1001:1000::/home/abc:/bin/bash
3. Use ':' as the delimiter to find the line where the third paragraph is equal to 0
答案：awk -F ':' '$3=="0" {print $0}' test
[root@lgs-01 awk]# awk -F ':' '$3=="0" {print $0}' test
root:x:0:0:root:/root:/bin/bash
4. Use ':' as the delimiter, find the line whose first paragraph is 'root', and replace the 'root' of the paragraph with 'toor' (can be used together with sed)
答案：awk -F ':' '$1=="root" {print $0}' test|sed -r 's/root/toor/g'
[root@lgs-01 awk]# awk -F ':' '$1=="root" {print $0}' test|sed -r 's/root/toor/g'
toor:x:0:0:toor:/toor:/bin/bash
5. Use ':' as a delimiter to print the last paragraph
答案：awk -F ':' '{print $NF}' test
[root@lgs-01 awk]# awk -F ':' '{print $NF}' test
/bin/bash
/sbin/nologin
/sbin/nologin
/sbin/nologin
/sbin/nologin
/bin/sync
/sbin/shutdown
/sbin/halt
/sbin/nologin
/sbin/nologin
/sbin/nologin
/sbin/nologin
/sbin/nologin
/sbin/nologin
/sbin/nologin
/sbin/nologin
/sbin/nologin
/sbin/nologin
/sbin/nologin
/bin/bash
/bin/bash
55
1
21
/user
/bin
34
t55abc
$!#
@user#
6. Print all lines with more than 20 lines
答案：awk -F ':' 'NR>20 {print $0}' test
[root@lgs-01 awk]# awk -F ':' 'NR>20 {print $0}' test
abc:x:1001:1000::/home/abc:/bin/bash
12:22:55
587:1
12:21
2:2:1:fsfs:root:/bin/:/user
342:x:3d:fafa:toor:/user:/bin
xx:xx:xx:xx:xx:xx:34
rr:rr:rr:rr:rr:rr:t55abc
##:#34#:bb:bb:bb:%pp^:$!#
#234#:vv:vv:vv:vv:ds:@user#
7. Use ':' as a delimiter to print all lines whose third paragraph is less than the fourth paragraph
答案：awk -F ':' '$3<$4 {print $0}' test
[root@lgs-01 awk]# awk -F ':' '$3<$4 {print $0}' test
adm:x:3:4:adm:/var/adm:/sbin/nologin
lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
games:x:12:100:games:/usr/games:/sbin/nologin
ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin
2:2:1:fsfs:root:/bin/:/user
342:x:3d:fafa:toor:/user:/bin
8. Use ':' as a delimiter, print the first and last paragraphs, and connect them with '@' (for example, the first line should be of the form 'root@/bin/bash')
答案：awk -F ':' '{print$1"@"$NF}' test
[root@lgs-01 awk]# awk -F ':' '{print$1"@"$NF}' test
root@/bin/bash
bin@/sbin/nologin
daemon@/sbin/nologin
adm@/sbin/nologin
lp@/sbin/nologin
sync@/bin/sync
shutdown@/sbin/shutdown
halt@/sbin/halt
mail@/sbin/nologin
operator@/sbin/nologin
games@/sbin/nologin
ftp@/sbin/nologin
nobody@/sbin/nologin
systemd-network@/sbin/nologin
dbus@/sbin/nologin
polkitd@/sbin/nologin
postfix@/sbin/nologin
sshd@/sbin/nologin
chrony@/sbin/nologin
lgs@/bin/bash
abc@/bin/bash
12@55
587@1
12@21
2@/user
342@/bin
xx@34
rr@t55abc
##@$!#
#234#@@user#
9. Using ':' as a delimiter, add the fourth paragraph of the entire document and sum up
答案：awk -F ':' '{(sum=sum+$4)};END{print sum}' test
[root@lgs-01 awk]# awk -F ':' '{(sum=sum+$4)};END{print sum}' test
4704