1. 顯示/etc/passwd檔案中以bash結尾的行
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[root@www ~]# grep -n '\(bash\)$' /etc/passwd
1:root:x:0:0:root:/root:/bin/bash
38:Allen:x:500:500:Allen.Huang:/home/Allen:/bin/bash
2. 顯示/etc/passwd檔案中的兩位數或三位數
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[root@www ~]# grep -n '[[:digit:]]\{2,3\}' /etc/passwd
9:mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
10:uucp:x:10:14:uucp:/var/spool/uucp:/sbin/nologin
11:operator:x:11:0:operator:/root:/sbin/nologin
12:games:x:12:100:games:/usr/games:/sbin/nologin
13:gopher:x:13:30:gopher:/var/gopher:/sbin/nologin
14:ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin
15:nobody:x:99:99:Nobody:/:/sbin/nologin
16:dbus:x:81:81:System message bus:/:/sbin/nologin
17:usbmuxd:x:113:113:usbmuxd user:/:/sbin/nologin
18:rpc:x:32:32:Rpcbind Daemon:/var/cache/rpcbind:/sbin/nologin
19:oprofile:x:16:16:Special user account to be used by OProfile:/home/oprofile:/sbin/nologin
20:vcsa:x:69:69:virtual console memory owner:/dev:/sbin/nologin
21:rtkit:x:499:497:RealtimeKit:/proc:/sbin/nologin
22:abrt:x:173:173::/etc/abrt:/sbin/nologin
23:hsqldb:x:96:96::/var/lib/hsqldb:/sbin/nologin
24:avahi-autoipd:x:170:170:Avahi IPv4LL Stack:/var/lib/avahi-autoipd:/sbin/nologin
25:saslauth:x:498:76:Saslauthd user:/var/empty/saslauth:/sbin/nologin
26:rpcuser:x:29:29:RPC Service User:/var/lib/nfs:/sbin/nologin
27:nfsnobody:x:65534:65534:Anonymous NFS User:/var/lib/nfs:/sbin/nologin
28:postfix:x:89:89::/var/spool/postfix:/sbin/nologin
29:haldaemon:x:68:68:HAL daemon:/:/sbin/nologin
30:gdm:x:42:42::/var/lib/gdm:/sbin/nologin
31:ntp:x:38:38::/etc/ntp:/sbin/nologin
32:apache:x:48:48:Apache:/var/www:/sbin/nologin
33:radvd:x:75:75:radvd user:/:/sbin/nologin
34:pulse:x:497:495:PulseAudio System Daemon:/var/run/pulse:/sbin/nologin
35:qemu:x:107:107:qemu user:/:/sbin/nologin
36:sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin
37:tcpdump:x:72:72::/:/sbin/nologin
3. 顯示‘netstat -tan’指令結果中以‘LISTEN’後跟0個、1個或多個空白字元結尾的行
[root@www ~]# netstat -tan | grep -n "LISTEN[[:space:]]*$"
3:tcp 0 0 127.0.0.1:6013 0.0.0.0:* LISTEN
4:tcp 0 0 0.0.0.0:2222 0.0.0.0:* LISTEN
5:tcp 0 0 0.0.0.0:111 0.0.0.0:* LISTEN
6:tcp 0 0 0.0.0.0:41811 0.0.0.0:* LISTEN
7:tcp 0 0 192.168.122.1:53 0.0.0.0:* LISTEN
8:tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN
9:tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN
10:tcp 0 0 127.0.0.1:6012 0.0.0.0:* LISTEN
12:tcp 0 0 ::1:6013 :::* LISTEN
13:tcp 0 0 :::2222 :::* LISTEN
14:tcp 0 0 :::111 :::* LISTEN
15:tcp 0 0 ::1:631 :::* LISTEN
16:tcp 0 0 ::1:25 :::* LISTEN
17:tcp 0 0 :::42138 :::* LISTEN
18:tcp 0 0 ::1:6012 :::* LISTEN
4. 添加使用者bash, testbash, basher以及nologin使用者（nologin使用者的shell為/sbin/nologin）,而後找出/etc/passwd檔案中使用者名同shell名的行
[root@www ~]# useradd bash
[root@www ~]# useradd testbash
[root@www ~]# useradd basher
[root@www ~]# useradd nologin -s /sbin/nologin
[root@www ~]# grep -n '^\(\b[[:alnum:]]\{1,\}\b\):.*\1$' /etc/passwd
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
39:bash:x:501:501::/home/bash:/bin/bash
42:nologin:x:504:504::/home/nologin:/sbin/nologin
5. 顯示目前系統上root、centos或user1使用者的預設的shell和UID
[root@www ~]# egrep '^\b(root|centos|user1)\b' /etc/passwd |cut -d: -f3,7
0:/bin/bash
503:/bin/bash
504:/bin/bash
6. 找出/etc/rc.d/init.d/functions檔案中某單詞（單詞中間可以存在下劃線）後面跟着一組小括号的行
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[root@www ~]# egrep -n --color '^(\b(\w{1,})\b)\(\)' /etc/rc.d/init.d/functions
54:fstab_decode_str() {
59:checkpid() {
68:__readlink() {
72:__fgrep() {
87:__umount_loop() {
115:__umount_loopback_loop() {
148:__pids_var_run() {
184:__pids_pidof() {
191:daemon() {
281:killproc() {
382:pidfileofproc() {
397:pidofproc() {
423:status() {
487:echo_success() {
498:echo_failure() {
509:echo_passed() {
520:echo_warning() {
532:update_boot_stage() {
540:success() {
546:failure() {
554:passed() {
561:warning() {
568:action() {
581:action_silent() {
594:strstr() {
600:confirm() {
618:get_numeric_dev() {
629:is_ignored_file() {
639:is_true() {
649:is_false() {
659:apply_sysctl() {
667:key_is_random() {
672:find_crypto_mount_point() {
685:init_crypto() {
7. 使用echo輸出一個路徑，而後egrep找出其路徑基名，進一步地使用egrep取出其目錄名
[root@www ~]# echo /etc/sysconfig/network/ | egrep -o --color '[[:alpha:]]+/?$' |cut -d/ -f1
network
[root@www ~]# echo /etc/sysconfig/network/ | egrep -o --color '^(/)\b.*\1\b'
/etc/sysconfig/
[root@www ~]# echo /etc/sysconfig/network/ | egrep -o --color '^(/)\b.*\1\b' |cut -d/ -f1-3
/etc/sysconfig
8. 找出ifconfig指令執行結果中1-255之間的數字
[root@www ~]# ifconfig | egrep --color '\b([1-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\b'
eth0 Link encap:Ethernet HWaddr 00:0C:29:A6:0E:39
inet addr:172.16.10.101 Bcast:172.16.10.255 Mask:255.255.255.0
inet6 addr: fe80::20c:29ff:fea6:e39/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX bytes:2573958 (2.4 MiB) TX bytes:2567184 (2.4 MiB)
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:12 errors:0 dropped:0 overruns:0 frame:0
TX packets:12 errors:0 dropped:0 overruns:0 carrier:0
virbr0 Link encap:Ethernet HWaddr 52:54:00:6F:2D:C1
inet addr:192.168.122.1 Bcast:192.168.122.255 Mask:255.255.255.0
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