Linux commands which shell

4 Ways to Check Which Shell You are Using on Linux

Out of the box, Linux provides a wide variety of shells. There is bash (Bourne Again shell) shell which ships by default in many Linux distributions. We also have sh (Bourne Shell), tcsh (TC shell), csh (C shell), Zsh (Z shell) and ksh (Korn Shell).

Curious to know which shell you are using on your Linux system? In this guide, we explore different ways that you can use to check which shell you are currently using in Linux.

1) Using echo command

The Linux echo command is a built-in command that is used to print the output of a string which is passed as an argument. Additionally, you can use the echo command to check the shell that you are running commands in. To accomplish this, execute:

The output shows that I am using the bash shell. Additionally, you can simply run the command:

To get the PID of the shell that you are currently in, run:

2) Using ps command

Commonly used for listing running processes, the ps command in its basic format sheds light on the shell that you are using. Simply execute the command:

From the first line of the output, we can clearly see the PID of the shell and the last column prints out the type of shell, in this case — bash.

Alternatively, you can run the command:

You can also use ps -p $$ -o args= which output just the shell name.

3) By viewing /etc/passwd file

The grep command can be used to probe the /etc/passwd file that contains attributes of the users such as username, user ID and group ID.

To display the shell used, invoke the command:

At the very last segment, we get to see the bash used, in this case /bin/bash This also gives you a glimpse of which shell is opened first when you first log in to your system.

4) Using lsof command

Ordinarily, the lsof command, short for list of open files, is used to provide a list of open files on your system. However, when used with the -p $$ flag, it gives a pointer to the shell you are in when you look at the first column of the output.

For example, we can clearly see that we are on the bash shell.

How to check the valid login shells

We have seen various ways that you can employ to check the shell that you are currently in. If you want to know the valid shells on your system, check the /etc/shells file, This file will provide you with the full pathnames of valid login shells in your system. Using the cat command, view the file as shown:

Conclusion

In this guide, we have shared simple but nifty ways that you can use to know which shell you are working on. This is important when writing scripts so that you can know how to start off writing the shebang header. We do hope that this tutorial was beneficial. Send us a shout and don’t forget to share this guide on your social platforms.

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How do I find out what shell I am using on Linux/Unix?

B oth Linux and Unix provides various shell out of the box. One can find bash (Bourne Again shell), ksh (Korn shell), csh (C shell)/tcsh (TC shell), sh (Bourne shell) and more installed by default. However, how do you check which shell am I using? What is the best way to find out what shell I am using on Linux? The echo $SHELL is not so reliable. This page explains how to find out which shell I am using at a Linux, MacOS, FreeBSD, or Unix-like systems.

How can I find out what shell I am using?

The following echo command or printf command should work:
echo «$SHELL»
OR
printf «My current shell — %s\n» «$SHELL»
Please note that $SHELL is the shell for the current user but not necessarily the shell that is running at the moment. Try the following examples

How do I check which shell am I using?

Here is another old good Unix trick. Use the ps command with -p option. The following command selects the processes whose process ID numbers appear in pid. Use the following command to find out which shell you are in:
ps -p $$
Sample outputs:

So what is a $ argument passed to the -p option? Remember $ returns the PID (process identification number) of the current process, and the current process is your shell. So running a ps on that number displays a process status listing of your shell. In that listing, you will find the name of your shell (look for CMD column).
ps -p $$
Sample outputs:

From my Linux box:
ps -p $$
Sample outputs:

You can store your shell name in a variable as follows :
MYSHELL=`ps -hp $$|awk ‘‘`
Please note those are backquotes, not apostrophes. Or better try out the following if you have a bash shell:
MYSHELL=$(ps -hp $$|awk ‘‘)
Another option is as follows:
echo $0
OR
printf «%s\n» $0
Sample outputs from the above commands:

Fig.01: Linux check which shell am I using

How do I check how many shells are installed on my Linux box?

The /etc/shells is a text file which contains the full pathnames of valid login shells. Type the following [nixmd name=”cat”] to see list how many shells are installed on your Linux or Unix box:
cat /etc/shells

Use /etc/shells file to check how many shells are installed on your system

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Okay, so when I open the Terminal app, which shell is opened by default?

Your default shell is defined in /etc/passwd file. So try the following grep command:

How to check which shell am I using:

Use the following Linux or Unix commands:

1. ps -p $$ – Display your current shell name reliably.
2. echo «$SHELL» – Print the shell for the current user but not necessarily the shell that is running at the movement.
3. echo $0 – Another reliable and simple method to get the current shell interpreter name on Linux or Unix-like systems.
4. readlink /proc/$$/exe – Another option to get the current shell name reliably on Linux operating systems.
5. cat /etc/shells – List pathnames of valid login shells currently installed
6. grep «^$USER» /etc/passwd – Print the default shell name. The default shell runs when you open a terminal window.
7. chsh -s /bin/ksh – Change the shell used from /bin/bash (default) to /bin/ksh for your account

Conclusion

Sometimes things are not easy as they seem, and this page is the perfect example of it. I hope you found the suggestion useful when it comes to checking your current running shell. Bash users can display shell version by typing the following command:
$ bash —version
Here is what I got from my Ubuntu Linux 20.04 LTS desktop:

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Linux Shell Commands

The Shell is the command interpreter on Linux systems. This document intoduces some of the basic features of the Shell and lists many of the commands or programs available on the Linux computers in Cardiff School of Computer Science & Informatics.

The Shell

The Linux command interpreter or shell is the program users interact with in a terminal emulation window. The terminal emulation window can be one in the workstation’s Graphical User Interface mate-terminal on Linux. Alternatively, it can be an application such as SSH secure shell client or PuTTY on a Windows PC that’s logged into Linux over the network.

The shell used in the School of Computer Science & Informatics is bash Bourne Again Shell. There are other shells available such as the Bourne Shell, the C-Shell and the TC-Shell, and you can choose to use a different shell if you prefer. They all have similar characteristics but each has its own particular features. This document assumes you are using bash .

Bash has the following features:

A command prompt which may be configured by the user. The default prompt is a dollar symbol preceded by «bash» and the bash program’s version number.

/bin containing the following.

/bin/countc
bash-2.05$ countc
45

516 ls -lrt
517 ps -ef
518 pdflatex myfile.tex

See the manual page on bash for more details (type man bash ).

Bash has an additional mechanism which allows you to recall and edit previous commands using the keyboard up-arrow key. If you press up-arrow, the last command re-appears on the terminal. Press up-arrow again to get earlier commands. To rerun the command, press RETURN . To amend the command before rerunning it, use the delete key to remove characters from the end or use the back-arrow key to reposition the cursor to delete or insert characters within the command.

Shell Commands

Here is a summary of some of the commands available. For more details refer to the manual page of each command. You can see these on-line by using the man command. Just type man followed by the name of the command you want to see.

Logging out

Command	Description
logout	log out of a Linux terminal

Note, on a Linux workstation you will need to exit the Desktop Environment instead.

Files and Directories

These commands allow you to create directories and handle files.

Command	Description
cat	concatenate and print data
lpr	spool file for line printing
cd	change current directory
lprm, cancel	remove jobs from line printer queue
chgrp	change file group
ls	list and generate statistics for files
chmod	change file mode
mkdir	make a new directory
cp	copy file data
more, page	display file data at your terminal

Command	Description
file	determine file type
mv	move or rename files
find	find files
pwd	print working directory
grep	search file for regular expression
rm, rmdir	remove (unlink) files or directories
head	give first few lines
tail	print last lines from file
just	text justification program
touch	update access and modification times of a file
lpq	spool queue examination program

File Editors

Editors are used to create and amend files.

Command	Description
emacs	GNU project Emacs
xemacs	emacs with mouse action
ex, edit	line editor

Command	Description
pico	easy text editor for vdus
pluma	Mate GUI text editor
gedit	GNOME text editor
vi, vim	standard text editor

Vi , pico and emacs are screen-based editors which run on a vdu or in a workstations terminal emulation window; pluma , gedit and xemacs are graphical user interface (GUI) based editors with cut and paste and mouse-controlled cursor positioning.

Manipulating data

The contents of files can be compared and altered with the following commands.

Command	Description
awk	pattern scanning and processing language
perl	data manipulation language
cmp	compare the contents of two files
paste	merge file data
comm	compare sorted data
sed	stream text editor
cut	cut out selected fields of each line of a file
sort	sort file data
diff	differential file comparator

Command	Description
split	split file into smaller files
expand, unexpand	expand tabs to spaces, and vice versa
tr	translate characters
gawk	pattern scanning and processing language
uniq	report repeated lines in a file
join	join files on some common field
look	find lines in sorted data
wc	count words, lines, and characters

Compressed files

Files may be compressed to save space. Compressed files can be created and examined.

Command	Description
gzip	compress files
zmore	file perusal filter for crt viewing of compressed text
uncompress	uncompress files

Command	Description
zcat	cat a compressed file
gunzip	uncompress gzipped files
zcmp, zdiff	compare compressed files

Information

Manuals and documentation are available on-line. Go to our web site www.cs.cf.ac.uk/systems for web-based documentation. The following Shell commands give information.

Command	Description
apropos	locate commands by keyword lookup
man	displays manual pages online

Command	Description
info	displays command information pages online
yelp	GNOME help viewer

Status

These commands list or alter information about the system.

Command	Description
ps	print process status statistics
date	print the date
quota -v	display disk usage and limits
reset	reset terminal mode
du	print amount of disk usage
script	keep script of terminal session
stty	set terminal options
groups	show group memberships
time	time a command
homequota	show quota and file usage
iostat	report I/O statistics
tty	print current terminal name

Command	Description
kill	send a signal to a process
uptime	display system status
last	show last logins of users
users	print names of logged in users
lun	list user names or login ID
vmstat	report virtual memory statistics
netstat	show network status
w	show what logged in users are doing
who	list logged in users
printenv	display value of a shell variable

Printing

Files can be printed using shell commands, using the GUI print manager, or direct from some applications.

You must specify a printer by name. Printers are called

Printer Name	Location
tl1_lw	Teaching Lab 1 (C/2.04) laser printer
tl3_lw	Teaching Lab 3 (C/2.08) laser printer

Printer Name	Location
tl2_lw	Teaching Lab 2 (C/2.05) laser printer
tl4_lw	Teaching Lab 4 (C/2.10) laser printer

Most commands which can be used to print files, expect the printer name to be given following a -P argument.

Files may be sent to the printers as simple text files or they may be processed in various ways for the laser printers.

Command	Description
lpr -P printer	send a file to a printer
dvips -P printer	postprocess TeX file into Postscript and print on laser printer
a2ps -P printer	format text file in PostScript and print on laser printer

Messages between Users

The Linux systems support on-screen messages to other users and world-wide electronic mail.

Command	Description
write	send a message to another local user
wall	send a message to all local users

Command	Description
pine	vdu-based mail utility
mail	simple send or read mail program
thunderbird	GUI mail handling tool on Linux

Networking

The School of Computer Science & Informatics is connected to the JANET Internet Protocol Service (JIPS), the UK Universities’ network.

These commands are used to send and receive files from Campus Linux hosts and from other hosts on JIPS and the Internet, that permit such connections, around the world.

Command	Description
ftp	file transfer program
tftp	trivial file transfer program
sftp	secure shell file transfer program
rcp	remote file copy
scp	secure shell remote file copy
wget	non-interactive network downloader

Command	Description
telnet	make terminal connection to another host
ssh	secure shell terminal or command connection
rlogin	remote login to a Linux host
rsh	remote shell
curl	transfer data from a url
firefox	web browser
google-chrome	web browser

These commands work only where the remote host permits such connections.

Programming

The following programming tools and languages are available.

General

Command	Description
make	maintain groups of programs
size	print program’s sizes

Command	Description
nm	print program’s name list
strip	remove symbol table and relocation bits

Command	Description
cb	C program beautifier
gcc	GNU ANSI C Compiler

Command	Description
ctrace	C program debugger
indent	indent and format C program source
cxref	generate C program cross reference

Command	Description
g++	GNU C++ Compiler

Command	Description
appletviewer	JAVA applet viewer
javac	JAVA compiler
eclipse	Java integrated development environment on Linux

FORTRAN

Command	Description
f95	GNU Fortran 95 compiler

Other Languages

(Not available on all systems).

Command	Description
bc	interactive arithmetic language processor
matlab	maths package
gcl	GNU Common Lisp
perl	general purpose language

Command	Description
python	object-oriented programming language
squeak	smalltalk
php	web page embedded language
mathematica	symbolic maths package
asp	web page embedded language

Text Processing

TeX is a typesetting language used extensively in Linux and other operating systems for producing high-quality printed documents. Another set of programs based on Troff is the standard Linux text formatting family used, for example to format manual pages.

General Commands

Command	Description
fmt	simple text formatter
evince	GNOME PostScript previewer

Command	Description
acroread	PDF viewer
spell	check text for spelling error
aspell	interactive spelling checker

Troff

Command	Description
eqn	mathematical preprocessor for troff
tbl	prepare tables for nroff or troff
grap	pic preprocessor for drawing graphs
troff	text formatting and typesetting language

Command	Description
nroff	text formatting language
groff	GNU troff interface for laserprinting
pic	troff preprocessor for drawing pictures

Command	Description
tex	text formatting and typesetting
latex	latex formatter

Command	Description
pdflatex	latex formatter with PDF output
xdvi	dvi previewer
dvips	convert a DVI file to POSTSCRIPT

Word Processing

LibreOffice is available on the School’s Linux systems and attempts compatibilty with Microsoft Office.

Command	Description
libreoffice	start LibreOffice applications

Database Management

MySQL and Oracle are available.

Command	Description
sqlplus	run the Oracle SQL interpreter
mysql	run the mysql SQL interpreter
sqldeveloper	Oracle SQL Developer GUI interface
mysql-workbench	GUI interface for MySQL

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