7. Shells

We are all familiar with the Bourne Again SHell, but there are two other user interfaces that are considered useful modern shells – the Berkeley Unix C shell and the Korn shell. This chapter installs packages compatible with these additional shell types.

7.1 Dash-0.5.12

Introduction to Dash

Dash is a POSIX compliant shell. It can be installed as /bin/sh or as the default shell for either root or a second user with a userid of 0. It depends on fewer libraries than the Bash shell and is therefore less likely to be affected by an upgrade problem or disk failure. Dash is also useful for checking that a script is completely compatible with POSIX syntax.

This package is known to build and work properly using an LFS 11.3 platform.

Package Information

Dash Dependencies

Optional

libedit (command line editor library)

User Notes: https://wiki.linuxfromscratch.org/blfs/wiki/dash

Installation of Dash

Install Dash by running the following commands:

./configure --bindir=/bin --mandir=/usr/share/man &&
make

This package does not come with a test suite.

Now, as the root user:

make install

If you would like to make dash the default sh, recreate the /bin/sh symlink as the root user:

Note

If you create the symbolic link from dash to sh, you will need to reset the link to bash to build LFS.

ln -svf dash /bin/sh

Command Explanations

--bindir=/bin: This parameter places the dash binary into the root filesystem.

--with-libedit: To compile Dash with libedit support.

Configuring Dash

###

Config Files

Dash sources /etc/profile and ~/.profile

Configuration Information

Update /etc/shells to include the Dash shell by issuing the following command as the root user:

cat >> /etc/shells << "EOF"
/bin/dash
EOF

Contents

Installed Program: dash

Installed Libraries: None

Installed Directories: None

Short Description

dash is a POSIX compliant shell.

7.2 Tcsh-6.24.07

Introduction to Tcsh

The Tcsh package contains “an enhanced but completely compatible version of the Berkeley Unix C shell (csh)”. This is useful as an alternative shell for those who prefer C syntax to that of the bash shell, and also because some programs require the C shell in order to perform installation tasks.

This package is known to build and work properly using an LFS 11.3 platform.

Package Information

User Notes: https://wiki.linuxfromscratch.org/blfs/wiki/tcsh

Installation of Tcsh

Install Tcsh by running the following commands:

./configure --prefix=/usr &&
make

To test the results, issue: make check.

Now, as the root user:

make install install.man &&

ln -v -sf tcsh   /bin/csh &&
ln -v -sf tcsh.1 /usr/share/man/man1/csh.1

Command Explanations

ln -v -sf tcsh /bin/csh: The FHS states that if there is a C shell installed, there should be a symlink from /bin/csh to it. This creates that symlink.

Configuring Tcsh

###

Config Files

There are numerous configuration files for the C shell. Examples of these are /etc/csh.cshrc, /etc/csh.login, /etc/csh.logout, ~/.tcshrc, ~/.cshrc, ~/.history, ~/.cshdirs, ~/.login, and ~/.logout. More information on these files can be found in the tcsh(1) man page.

Configuration Information

Update /etc/shells to include the C shell program names (as the root user):

cat >> /etc/shells << "EOF"
/bin/tcsh
/bin/csh
EOF

The following ~/.cshrc provides two alternative colour prompts and coloured ls output. If you prefer a global modification, issue the command as the root user, replacing ~/.cshrc by /etc/csh.cshrc.

cat > ~/.cshrc << "EOF"
# Original at:
# https://www.cs.umd.edu/~srhuang/teaching/code_snippets/prompt_color.tcsh.html

# Modified by the BLFS Development Team.

# Add these lines to your ~/.cshrc (or to /etc/csh.cshrc).

# Colors!
set     red="%{\033[1;31m%}"
set   green="%{\033[0;32m%}"
set  yellow="%{\033[1;33m%}"
set    blue="%{\033[1;34m%}"
set magenta="%{\033[1;35m%}"
set    cyan="%{\033[1;36m%}"
set   white="%{\033[0;37m%}"
set     end="%{\033[0m%}" # This is needed at the end...

# Setting the actual prompt.  Two separate versions for you to try, pick
# whichever one you like better, and change the colors as you want.
# Just don't mess with the ${end} guy in either line...  Comment out or
# delete the prompt you don't use.

set prompt="${green}%n${blue}@%m ${white}%~ ${green}%%${end} "
set prompt="[${green}%n${blue}@%m ${white}%~ ]${end} "

# This was not in the original URL above
# Provides coloured ls
alias ls ls --color=always

# Clean up after ourselves...
unset red green yellow blue magenta cyan yellow white end
EOF

Contents

Installed Program: tcsh

Installed Libraries: None

Installed Directory: None

Short Descriptions

tcsh is an enhanced but completely compatible version of the Berkeley Unix C shell, csh. It is usable as both an interactive shell and a script processor.

7.3 zsh-5.9

Introduction to zsh

The zsh package contains a command interpreter (shell) usable as an interactive login shell and as a shell script command processor. Of the standard shells, zsh most closely resembles ksh but includes many enhancements.

This package is known to build and work properly using an LFS 11.3 platform.

Package Information

Additional Downloads

Note

When there is a new zsh release, the old files shown above are moved to a new server directory: https://www.zsh.org/pub/old/.

zsh Dependencies

Optional

PCRE-8.45 and Valgrind-3.20.0

User Notes: https://wiki.linuxfromscratch.org/blfs/wiki/zsh

Installation of zsh

If you downloaded the optional documentation, unpack it with the following command:

tar --strip-components=1 -xvf ../zsh-5.9-doc.tar.xz

Install zsh by running the following commands:

./configure --prefix=/usr            \
            --sysconfdir=/etc/zsh    \
            --enable-etcdir=/etc/zsh \
            --enable-cap             \
            --enable-gdbm                             &&
make                                                  &&

makeinfo  Doc/zsh.texi --plaintext -o Doc/zsh.txt     &&
makeinfo  Doc/zsh.texi --html      -o Doc/html        &&
makeinfo  Doc/zsh.texi --html --no-split --no-headers -o Doc/zsh.html

If you have texlive-20220321 installed, you can build PDF format of the documentation by issuing the following command:

texi2pdf  Doc/zsh.texi -o Doc/zsh.pdf

To test the results, issue: make check.

Now, as the root user:

make install                              &&
make infodir=/usr/share/info install.info &&

install -v -m755 -d                 /usr/share/doc/zsh-5.9/html &&
install -v -m644 Doc/html/*         /usr/share/doc/zsh-5.9/html &&
install -v -m644 Doc/zsh.{html,txt} /usr/share/doc/zsh-5.9

If you downloaded the optional documentation, install it by issuing the following commands as the root user:

make htmldir=/usr/share/doc/zsh-5.9/html install.html &&
install -v -m644 Doc/zsh.dvi /usr/share/doc/zsh-5.9

If you built the PDF format of the documentation, install it by issuing the following command as the root user:

install -v -m644 Doc/zsh.pdf /usr/share/doc/zsh-5.9

Command Explanations

--sysconfdir=/etc/zsh and --enable-etcdir=/etc/zsh: These parameters are used so that all the zsh configuration files are consolidated into the /etc/zsh directory. Omit these parameters if you wish to retain historical compatibility by having all the files located in the /etc directory.

--enable-cap: This option enables POSIX capabilities.

--enable-gdbm: This option enables the use of the GDBM library.

--enable-pcre: This option allows zsh to use the PCRE regular expression library in shell builtins.

Configuring zsh

Config Files

There are a whole host of configuration files for zsh including /etc/zsh/zshenv, /etc/zsh/zprofile, /etc/zsh/zshrc, /etc/zsh/zlogin and /etc/zsh/zlogout. You can find more information on these in the zsh(1) and related manual pages.

The first time zsh is executed, you will be prompted by messages asking several questions. The answers will be used to create a ~/.zshrc file. If you wish to run these questions again, run zsh /usr/share/zsh/5.9/functions/zsh-newuser-install -f.

There are several built-in advanced prompts. In the zsh shell, start advanced prompt support with autoload -U promptinit, then promptinit. Available prompt names are listed with prompt -l. Select a particular one with prompt <prompt-name>. Display all available prompts with prompt -p. Except for the list and display commands above, you can insert the other ones in ~/.zshrc to be automatically executed at shell start, with the prompt you chose.

Configuration Information

Update /etc/shells to include the zsh shell program names (as the root user):

cat >> /etc/shells << "EOF"
/bin/zsh
EOF

Contents

Installed Programs: zsh and zsh-5.9 (hardlinked to each other)

Installed Libraries: Numerous plugin helper modules under /usr/lib/zsh/5.9/

Installed Directories: /usr/{lib,share}/zsh and /usr/share/doc/zsh-5.9

Short Description

zsh is a shell which has command-line editing, built-in spelling correction, programmable command completion, shell functions (with autoloading), a history mechanism, and a host of other features.