I’d like to start doing some text processing (awk, grep, sed, etc.) with the command line on my computer (Mac). The default shell is Zsh but it is possible to change it to Bash although I’ve read that the Mac OS is installed with an older version of Bash by default.
I’m wondering if I should just practice with Zsh or if I should use Bash?
Thank you!
From uses of exec command in shell:
Whenever we run any command in a Bash shell, a subshell is created by default, and a new child process is spawned (forked) to execute the command. When using exec, however, the command following exec replaces the current shell. This means no subshell is created and the current process is replaced with this new command.
General command to start up a new shell with no subshell process
exec $SHELL
where $SHELL represent the path to the shell
On terminal, type and enter the following to run a new bash shell:
exec bash
or you change back to a new zsh shell by
exec zsh
Due to licensing issues, macOS shows a bash version 3.2.
$> bash --version
GNU bash, version 3.2.57(1)-release (x86_64-apple-darwin20)
Copyright (C) 2007 Free Software Foundation, Inc.
Newer versions of macOS (Starting from Catalina) now users
zshas default instead ofbash.
homebrew
/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
brew install bash
exec bash
Be careful: Your old bash 3 version would still be installed in
/bin/bashwhile the brew version would be in/usr/local/bin/bash. You can check which version you are using withecho $SHELLorwhich bash.
bash version$> bash --version
GNU bash, version 5.1.4(1)-release (x86_64-apple-darwin20.2.0)
Copyright (C) 2020 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
If you do not see the updated version, your path environment variable might need some rework.
Reload bash with full path into a new shell
exec $(echo $(brew --prefix)/bin/bash)
First, update the list of permitted shell by adding the bash brew version into /private/etc/shells.
$> echo $(brew --prefix)/bin/bash | sudo tee -a /private/etc/shells
/usr/local/bin/bash
To check /usr/local/bin/bash has been added to /private/etc/shells
$> cat /private/etc/shells
# List of acceptable shells for chpass(1).
# Ftpd will not allow users to connect who are not using
# one of these shells.
/bin/bash
/bin/csh
/bin/ksh
/bin/sh
/bin/tcsh
/bin/zsh
/usr/local/bin/bash
Finally, update your user’s shell with chpass command line.
$> sudo chpass -s /usr/local/bin/bash alvin
Changing shell for alvin.
Alternatively, instead of using
chpass, you can go to the Menu >System Preferences...>Users & Groups. Unlock the pane, control click on your user to selectAdvanced Options..., then update theLogin shellto/usr/local/bin/bash
There’s a big differences in how a command is used based on either Linux (GNU) or macOS (BSD) version of the command utilities.
awk, grep, sed in macOS most likely are BSD version.
In most tutorial you find online including DataQuest are based on GNU command utilities.
Regardless of whether you used BSD or GNU command utilities, ensure you use the right (BSD or GNU) documentation.
Guide to install GNU core utilities:
brew install coreutils findutils gnu-tar gnu-sed gawk gnutls gnu-indent gnu-getopt grep
There’s no best selection of shell choice. All about personal preferences.
Personally, I used bash because most OS and online tutorials uses Bash.
For bash, you need to have the following files on macOS:
~/.bashrc to initialize the bash interactive shell session.~/.bash_profile to load the path variables~/.profile for non-interactive shell session for commandsYou can read up on Why is bash the default shell in most OS?