RHEL / CentOS Linux install and activate Bash completion

How do I use bash auto complete features with various command on CentOS / RHEL / Fedora / Scientific Linux based systems?

Autocomplete is nothing but a collection of various hacks that specify how arguments are to be completed by Readline using complete built-in. By default, this feature is turned on many Linux distributions such as Debian Linux, Ubuntu Linux and more. However, this feature is not installed and turned on on RHEL based Linux distributions including CentOS Linux. This tutorials shows you how to install Bash Autocomplete feature on a CentOS/RHEL/Oracle/Scientific or Fedora Linux.

Packages to install and enable Bash completion on CentOS/RHEL

You need to install two packages:

  1. bash-completion: Programmable completion for Bash
  2. bash-completion-extras : Additional programmable completions for Bash (only for CentOS/RHEL/Oracle/SL v7.x)

RHEL / CentOS Linux install and activate Bash completion

First, turn on the EPEL repo on a CentOS/RHEL version 6 (if you are using CentOS/RHEL 7.x, see this page to turn on EPEL repo) and type the following yum command to install bash-completion package:
# yum install bash-completion
# yum install bash-completion bash-completion-extras
Sample outputs:

Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: ftp.iitm.ac.in
 * epel: ftp.cuhk.edu.hk
 * extras: ftp.iitm.ac.in
 * updates: ftp.iitm.ac.in
Resolving Dependencies
--> Running transaction check
---> Package bash-completion.noarch 1:2.1-6.el7 will be installed
---> Package bash-completion-extras.noarch 1:2.1-11.el7 will be installed
--> Finished Dependency Resolution
Dependencies Resolved
 Package                            Arch               Version                  Repository        Size
 bash-completion                    noarch             1:2.1-6.el7              base              85 k
 bash-completion-extras             noarch             1:2.1-11.el7             epel             123 k
Transaction Summary
Install  2 Packages
Total download size: 208 k
Installed size: 648 k
Is this ok [y/d/N]: y
Downloading packages:
(1/2): bash-completion-2.1-6.el7.noarch.rpm                                     |  85 kB  00:00:03     
(2/2): bash-completion-extras-2.1-11.el7.noarch.rpm                             | 123 kB  00:00:07     
Total                                                                   26 kB/s | 208 kB  00:00:07     
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  Installing : 1:bash-completion-2.1-6.el7.noarch                                                  1/2 
  Installing : 1:bash-completion-extras-2.1-11.el7.noarch                                          2/2 
  Verifying  : 1:bash-completion-extras-2.1-11.el7.noarch                                          1/2 
  Verifying  : 1:bash-completion-2.1-6.el7.noarch                                                  2/2 
  bash-completion.noarch 1:2.1-6.el7             bash-completion-extras.noarch 1:2.1-11.el7            

Fedora Linux user type the following dnf command:
$ sudo dnf install bash-completion

Related: How to install and enable Bash auto completion in Fedora Linux

How do I use bash Autocomplete feature?

Then exits a login shell / ssh session and log back in using the following command:
# logout
Open a terminal or log in using ssh:
$ ssh [email protected]
Alternatively, use the following command to source completion code for bash:
$ . /etc/bash_completion
$ source /etc/bash_completion
For newer version try:
$ source /etc/profile.d/bash_completion.sh

Usage examples

You need to simply press [TAB] key. The syntax is:

command [TAB]
command arg[TAB][TAB]
man da[TAB]

rpm usage

Type the following command (type rpm -qi ph followed by [TAB]):

$ rpm -qi ph[TAB][TAB]
php         php-cli     php-common  php-devel   php-imap

yum usage

Type the following command:

$ yum [TAB][TAB]
--assumeyes        --enableplugin     list               search
--cacheonly        --enablerepo       makecache          --setopt
check              --errorlevel       --nogpgcheck       shell
check-update       --exclude          --noplugins        --showduplicates
clean              groupinfo          --obsoletes        --skip-broken
--color            groupinstall       provides           --tolerant
--config           grouplist          --quiet            update
--debuglevel       groupremove        --randomwait       upgrade
deplist            help               reinstall          --verbose
--disableexcludes  --help             --releasever       version
--disableplugin    history            remove             --version
--disablerepo      info               repolist           
distro-sync        install            resolvedep         
downgrade          --installroot      --rpmverbosity 

To search a package called lsof:
$ yum se[TAB] lsof
Or search and install on fly:

# yum in[TAB] ls[TAB]
lshell.noarch            lslk-debuginfo.x86_64    lsscsi-debuginfo.x86_64
lshw-gui.x86_64          lslk.x86_64              lsscsi.x86_64
lshw.x86_64              lsof-debuginfo.x86_64    lsyncd.x86_64

cryptsetup usage

Linux Unified Key Setup-on-disk-format (LUKS) allows you to encrypt whole disks and you can use cryptsetup command to mount or remount encrypted partition:
cryptsetup [TAB] luksOpen /dev/md[TAB]
Sample outputs:

Fig.01: cryptsetup on RHEL based system

A list of all commands supported by Autocomplete feature

Type the following command:
$ cd /etc/bash_completion.d
$ ls

Sample outputs:

autoconf       gpg2               ntpdate           shadow
automake       gzip               open-iscsi        smartctl
bash-builtins  iconv              openssl           sqlite3
bind-utils     iftop              perl              ssh
brctl          ifupdown           pkg-config        strace
bzip2          info               pm-utils          subscription-manager
chkconfig      ipmitool           postfix           tar
configure      iproute2           procps            tcpdump
coreutils      iptables           python            util-linux
cpio           lsof               quota-tools       wireless-tools
crontab        lvm                redefine_filedir  xmllint
cryptsetup     lzma               rfkill            xmlwf
dd             make               rpm               xz
dhclient       man                rsync             yum.bash
e2fsprogs      mdadm              scl.bash          yum-utils.bash
findutils      module-init-tools  service
getent         net-tools          sh

Posted by: SXI ADMIN

The author is the creator of SXI LLC and a seasoned sysadmin, DevOps engineer, and a trainer for the Linux operating system/Unix shell scripting. Get the latest tutorials on SysAdmin, Linux/Unix and open source topics via RSS/XML feed or weekly email newsletter.