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在 Linux 系统中，nl命令用于计算文件中的行号。它可以将输出的文件内容自动加上行号，并且可以通过不同的选项来设置行号的显示方式，包括行号的位数、是否自动补齐 0 等。其命令格式为：nl(选项)…(文件)…。以下是一些常见的选项：
-b：指定行号指定的方式，主要有两种：-b a：表示不论是否为空行，也同样列出行号（类似cat -n）。-b t：如果有空行，空的那一行不要列出行号（默认值）。
-n：列出行号表示的方法，主要有三种：-n ln：行号在屏幕的最左方显示。-n rn：行号在屏幕的最右方显示，且行号从 1 开始计数。-n rn：行号在屏幕的最右方显示，且行号从 0 开始计数。
nl -b t /etc/selinux/config1 # This file controls the state of SELinux on the system.2 # SELINUX= can take one of these three values:3 # enforcing - SELinux security policy is enforced.4 # permissive - SELinux prints warnings instead of enforcing.5 # disabled - No SELinux policy is loaded.6 SELINUX=enforcing7 # SELINUXTYPE= can take one of three values:8 # targeted - Targeted processes are protected,9 # minimum - Modification of targeted policy. Only selected processes are protected.10 # mls - Multi Level Security protection.11 SELINUXTYPE=targetednl -n rz /etc/selinux/config000001 # This file controls the state of SELinux on the system.
000002 # SELINUX= can take one of these three values:
000003 # enforcing - SELinux security policy is enforced.
000004 # permissive - SELinux prints warnings instead of enforcing.
000005 # disabled - No SELinux policy is loaded.
000006 SELINUX=enforcing
000007 # SELINUXTYPE= can take one of three values:
000008 # targeted - Targeted processes are protected,
000009 # minimum - Modification of targeted policy. Only selected processes are protected.
000010 # mls - Multi Level Security protection.
000011 SELINUXTYPE=targeted
以下是使用nl命令的一些示例：
- 基本用法：
隐藏过程
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(root@centos79 test3)# cat a.txte38idfae83sggj2ztycgsgsa(root@centos79 test3)# nl a.txt1 e2 383 i4 d5 f6 a7 e8 839 s10 g11 g12 j13 214 z15 t16 y17 c18 g19 s20 g21 s22 a
-n rz选项：行号在屏幕的最右方显示，且行号从 0 开始计数。
隐藏过程
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(root@centos79 test3)# cat a.txte38idfae83sggj2ztycgsgsa(root@centos79 test3)# nl -n rz a.txt0 e1 382 i3 d4 f5 a6 e7 838 s9 g10 g11 j12 213 z14 t15 y16 c17 g18 s19 g20 s21 a
-w选项：指定行号的宽度。
隐藏过程
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(root@centos79 test3)# cat a.txte38idfae83sggj2ztycgsgsa(root@centos79 test3)# nl -n rz a.txt001 e002 38003 i004 d005 f006 a007 e008 83009 s010 g011 g012 j013 2014 z015 t016 y017 c018 g019 s020 g021 s022 a
-b选项：指定行号的显示方式。
隐藏过程
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(root@centos79 test3)# cat a.txte38idfae83sggj2ztycgsgsa(root@centos79 test3)# nl -b a a.txt1 e2 383 i4 d5 f6 a7 e8 839 s10 g11 g12 j13 214 z15 t16 y17 c18 g19 s20 g21 s22 a
plaintext
(root@centos79 test3)# cat a.txte38idfae83sggj2ztycgsgsa(root@centos79 test3)# nl -b t a.txt1 e2 383 i4 d5 f6 a7 e8 839 s10 g11 g12 j13 214 z15 t16 y17 c18 g19 s20 g21 s22 a
ls | nl1 adjtime2 aliases3 aliases.db4 alternatives5 anacrontab6 asound.conf7 audisp8 audit9 bash_completion.d10 bashrc
jps -l | nl1 4448 org.apache.zookeeper.server.quorum.QuorumPeerMain2 4622 sun.tools.jps.Jps
ps -ef | nl1 UID PID PPID C STIME TTY TIME CMD2 root 1 0 0 19:14 ? 00:00:04 /usr/lib/systemd/systemd --switched-root --s ystem --deserialize 223 root 2 0 0 19:14 ? 00:00:00 [kthreadd]4 root 3 2 0 19:14 ? 00:00:02 [ksoftirqd/0]5 root 5 2 0 19:14 ? 00:00:00 [kworker/0:0H]6 root 7 2 0 19:14 ? 00:00:00 [migration/0]7 root 8 2 0 19:14 ? 00:00:00 [rcu_bh]8 root 9 2 0 19:14 ? 00:00:03 [rcu_sched]
ps aux | nl1 USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND2 root 1 0.3 0.3 128168 6760 ? Ss 19:14 0:04 /usr/lib/systemd/systemd --switched-root --system --deserialize 223 root 2 0.0 0.0 0 0 ? S 19:14 0:00 [kthreadd]4 root 3 0.1 0.0 0 0 ? S 19:14 0:02 [ksoftirqd/0]5 root 5 0.0 0.0 0 0 ? S< 19:14 0:00 [kworker/0:0H]6 root 7 0.0 0.0 0 0 ? S 19:14 0:00 [migration/0]7 root 8 0.0 0.0 0 0 ? S 19:14 0:00 [rcu_bh]8 root 9 0.2 0.0 0 0 ? S 19:14 0:03 [rcu_sched]9 root 10 0.0 0.0 0 0 ? S< 19:14 0:00 [lru-add-drain]10 root 11 0.2 0.0 0 0 ? S 19:14 0:03 [watchdog/0]