In Linux, the tree command is used to print the specified N-level directory structure or file.

Ee view, especially when there are many small files, the headers displayed are all big. We need to view the specified level.
The default tree command is not installed. You need to install yum or apt-get separately. For more information about tree parameters, see tree-help. Below are some common parameters:
-C: color of the tree for easy display.
-D: displays only directories.
-L: displays the number of levels and key parameters.

For example, we can view the layer-3 files and directories under/etc:

[Root @ drlb etc] # tree-L 3
.
── Adjtime
── Aliases
── Aliases. db
── Alternatives
│ ── Bin-iptables-xml.x86_64-& gt;/bin/iptables-xml-1.4.7
│ ├ ── Ip6tables. x86_64-& gt;/sbin/ip6tables-1.4.7
│ ├ ── Iptables. x86_64-& gt;/sbin/iptables-1.4.7
│ ── Libip4tc000. x86_64-& gt;/lib64/libip4tc. so.0.0.0-1.4.7
│ ── Libip4tc0. x86_64-& gt;/lib64/libip4tc. so.0-1.4.7
│ ── Libip6tc000. x86_64-& gt;/lib64/libip6tc. so.0.0.0-1.4.7
│ ── Libip6tc0. x86_64-& gt;/lib64/libip6tc. so.0-1.4.7
│ ── Libipq000.x86 _ 64-& gt;/lib64/libipq. so.0.0.0-1.4.7
│ ── Libipq0.x86 _ 64-& gt;/lib64/libipq. so.0-1.4.7
│ ── Libiptc000.x86 _ 64-& gt;/lib64/libiptc. so.0.0.0-1.4.7
│ ── Libiptc0.x86 _ 64-& gt;/lib64/libiptc. so.0-1.4.7
│ ── Libnssckbi. so. x86_64-& gt;/usr/lib64/nss/libnssckbi. so
│ ── Libxtables400.x86 _ 64-& gt;/lib64/libxtables. so.4.0.0-1.4.7
│ ── Libxtables4.x86 _ 64-& gt;/lib64/libxtables. so.4-1.4.7
│ ├ ── Man-ip6tables-restore.x86_64-& gt;/usr/share/man/man8/ip6tables-restore-1.4.7.8.gz
│ ├ ── Man-ip6tables-save.x86_64-& gt;/usr/share/man/man8/ip6tables-save-1.4.7.8.gz
│ ├ ── Man-ip6tables.x86_64-& gt;/usr/share/man/man8/ip6tables-1.4.7.8.gz
│ ├ ── Man-iptables-restore.x86_64-& gt;/usr/share/man/man8/iptables-restore-1.4.7.8.gz
│ ├ ── Man-iptables-save.x86_64-& gt;/usr/share/man/man8/iptables-save-1.4.7.8.gz
│ ├ ── Man-iptables.x86_64-& gt;/usr/share/man/man8/iptables-1.4.7.8.gz
│ ├ ── Man-iptables-xml.x86_64-& gt;/usr/share/man/man8/iptables-xml-1.4.7.8.gz
│ ├ ── Mta-& gt;/usr/sbin/sendmail. postfix
│ ├ ── Mta-aliasesman-& gt;/usr/share/man/man5/aliases.postfix.5.gz
│ ├ ── Mta-mailq-& gt;/usr/bin/mailq. postfix
│ ├ ── Mta-mailqman-& gt;/usr/share/man/man1/mailq.postfix.1.gz
│ ├ ── Mta-newaliases-& gt;/usr/bin/newaliases. postfix
│ ├ ── Mta-newaliasesman-& gt;/usr/share/man/man1/newaliases.postfix.1.gz
│ ├ ── Mta-pam-& gt;/etc/pam. d/smtp. postfix
│ ├ ── Mta-rmail-& gt;/usr/bin/rmail. postfix
│ ├ ── Mta-sendmail-& gt;/usr/lib/sendmail. postfix
│ ├ ── Mta-sendmailman-& gt;/usr/share/man/man1/sendmail.postfix.1.gz
│ ├ ── Sbin-ip6tables-multi.x86_64-& gt;/sbin/ip6tables-multi-1.4.7
│ ├ ── Sbin-ip6tables-restore.x86_64-& gt;/sbin/ip6tables-restore-1.4.7
│ ├ ── Sbin-ip6tables-save.x86_64-& gt;/sbin/ip6tables-save-1.4.7
│ ├ ── Sbin-iptables-multi.x86_64-& gt;/sbin/iptables-multi-1.4.7
│ ├ ── Sbin-iptables-restore.x86_64-& gt;/sbin/iptables-restore-1.4.7
│ └ ── Sbin-iptables-save.x86_64-& gt;/sbin/iptables-save-1.4.7
── Anacrontab
├ ── Audisp
│ ── Audispd. conf
│ ── Plugins. d
│ ── Af_unix.conf
│ ── Syslog. conf
├ ── Audit
│ ── Auditd. conf
│ └ ── Audit. rules
── Bash_completion.d
│ ── Gdbus-bash-completion.sh.
│ ── Gsettings-bash-completion.sh.
│ ── Salt. bash
│ ── Yum. bash
│ ── Yum-utils.bash.
├ ── Bashrc
── Blkid
│ ── Blkid. tab
├ ── Centos-release
── Chkconfig. d
── Cron. d
│ ── 0 hourly
│ ── Raid-check
│ ── Vnstat
── Cron. daily
│ ── Logrotate
── Cron. deny
── Cron. hourly
│ ── 0 anacron
── Cron. monthly
── Crontab
── Cron. weekly
├ ── Crypttab
├ ── Csh. cshrc
── Csh. login
── Dbus-1
│ ── System. d
│ ── Upstart. conf
── Default
│ ── Nss
│ ── Useradd
── Depmod. d
│ ── Dist. conf
── Dhcp
│ ── Dhclient. d
── DIR_COLORS
── DIR_COLORS.256color
── DIR_COLORS.lightbgcolor
── Dracut. conf
── Dracut. conf. d
── Environment
── Ethers
── Exports
── Favicon.png-& gt;/usr/share/icons/hicolor/16x16/apps/system-logo-icon.png
── Filesystems
── Fonts
│ ── Conf. avail
│ ── 10-10-autohint.conf
│ ── 10-no-sub-pixel.conf
│ ── 10-10-sub-pixel-bgr.conf
│ ── 10-10-sub-pixel-rgb.conf
│ ── 10-10-sub-pixel-vbgr.conf
│ ── 10-10-sub-pixel-vrgb.conf
│ ── 10-10-unhinted.conf
│ ── 20-fix-globaladvance.conf
│ ── 20-unhint-small-vera.conf
│ ── 25-unhint-nonlatin.conf
│ ── 30-metric-aliases.conf
│ ── 30-urw-aliases.conf
│ ── 40-nonlatin.conf
│ ── 45-latin.conf
│ ── 49-sansserif.conf
│ ── 50-user.conf
│ ── 51-local.conf
│ ── 60-60-latin.conf
│ ── 65-fonts-persian.conf
│ ── 65-khmer.conf
│ ── 65-nonlatin.conf
│ ── 69-uniont.conf
│ ── 70-no-bitmaps.conf
│ ── 70-yes-bitmaps.conf
│ ── 80-delicious.conf
│ ── 90-synthetic.conf
│ ── Conf. d
│ ── 20-fix-globaladvance.conf-& gt;.../conf. avail/20-fix-globaladvance.conf
│ ── 20-unhint-small-vera.conf-& gt;.../conf. avail/20-unhint-small-vera.conf
│ ── 25-no-bitmap-dist.conf
│ ── 25-unhint-nonlatin.conf-& gt;.../conf. avail/25-unhint-nonlatin.conf
│ ── 30-metric-aliases.conf-& gt;.../conf. avail/30-metric-aliases.conf
│ ── 30-urw-aliases.conf-& gt; ../conf. avail/30-urw-aliases.conf
│ ── 40-nonlatin.conf-& gt;.../conf. avail/40-nonlatin.conf
│ ── 45-latin.conf-& gt;.../conf. avail/45-latin.conf
│ ── 49-sansserif.conf-& gt; ../conf. avail/49-sansserif.conf
│ ── 50-user.conf-& gt; ../conf. avail/50-user.conf
│ ── 51-local.conf-& gt; ../conf. avail/51-local.conf
│ ── 60-60-latin.conf-& gt; ../conf. avail/60-latin.conf
│ ── 65-fonts-persian.conf-& gt;.../conf. avail/65-fonts-persian.conf
│ ── 65-nonlatin.conf-& gt;.../conf. avail/65-nonlatin.conf
│ ── 69-uniont.conf-& gt;.../conf. avail/69-uniont.conf
│ ── 80-delicious.conf-& gt; ../conf. avail/80-delicious.conf
│ ── 90-synthetic.conf-& gt;.../conf. avail/90-synthetic.conf
│ ── README
│ ── Fonts. conf
│ ── Fonts. dtd
── Fstab
├ ── Gai. conf
├ ── Gcrypt
── Gnupg
── Group
── Group-
── Grub. conf-& gt; ../boot/grub. conf
── Gshadow
── Gshadow-
── Host. conf
── Hosts
── Hosts. allow
── Hosts. deny
── Init
│ ── Control-alt-delete.conf.
│ ── Init-system-dbus.conf.
│ ── Kexec-disable.conf.
│ ── Plymouth-shutdown.conf.
│ ├ ── Preofdm. conf
│ ── Quit-plymouth.conf.
│ ── Rc. conf
│ ── RcS. conf
│ ── RcS-emergency.conf.
│ ── RcS-sulogin.conf.
│ ── Serial. conf
│ ── Splash-manager.conf.
│ ── Start-ttys.conf.
│ ── Tty. conf
── Init. d-& gt; rc. d/init. d
── Inittab
── Inputrc
── Iproute2
│ ── Ematch_map
│ ── Rt_dsfield
│ ── Rt_protos
│ ── Rt_realms
│ ── Rt_scopes
│ ── Rt_tables
── Iscsi
│ ── Initiatorname. iscsi
│ ── Iscsid. conf
── Issue
── Issue.net
── Keepalived
│ ── Keepalived. conf
── Krb5.conf
 
If only the directory is displayed, we can use tree-d-L 3.

[Root @ drlb etc] # tree-d-L 3
.
── Alternatives
├ ── Audisp
│ ── Plugins. d
├ ── Audit
── Bash_completion.d
── Blkid
── Chkconfig. d
── Cron. d
── Cron. daily
── Cron. hourly
── Cron. monthly
── Cron. weekly
── Dbus-1
│ ── System. d
── Default
── Depmod. d
── Dhcp
│ ── Dhclient. d
── Dracut. conf. d
── Fonts
│ ── Conf. avail
│ ── Conf. d
├ ── Gcrypt
── Gnupg
── Init
── Init. d-& gt; rc. d/init. d
── Iproute2
── Iscsi
── Keepalived
 
If you add a color display, you can add the-C parameter for more intuitive viewing.