The Bash Shell Startup Files

http://www.linuxfromscratch.org/blfs/view/6.3/postlfs/profile.html

The shell program /bin/bash (hereafter referred to as just "the shell") uses a collection of startup files to help create an environment. Each file has a specific use and may affect login and interactive environments differently. The files in the /etc directory generally provide global settings. If an equivalent file exists in your home directory it may override the global settings.

An interactive login shell is started after a successful login, using /bin/login, by reading the /etc/passwd file. This shell invocation normally reads /etc/profileand its private equivalent ~/.bash_profile upon startup.

An interactive non-login shell is normally started at the command-line using a shell program (e.g., [prompt]$/bin/bash) or by the /bin/su command. An interactive non-login shell is also started with a terminal program such as xterm or konsole from within a graphical environment. This type of shell invocation normally copies the parent environment and then reads the user's ~/.bashrc file for additional startup configuration instructions.

A non-interactive shell is usually present when a shell script is running. It is non-interactive because it is processing a script and not waiting for user input between commands. For these shell invocations, only the environment inherited from the parent shell is used.

The file ~/.bash_logout is not used for an invocation of the shell. It is read and executed when a user exits from an interactive login shell.

Many distributions use /etc/bashrc for system wide initialization of non-login shells. This file is usually called from the user's ~/.bashrc file and is not built directly into bash itself. This convention is followed in this section.

For more information see info bash -- Nodes: Bash Startup Files and Interactive Shells.

Note

Most of the instructions below are used to create files located in the /etc directory structure which requires you to execute the commands as the root user. If you elect to create the files in user's home directories instead, you should run the commands as an unprivileged user.

/etc/profile

Here is a base /etc/profile. This file starts by setting up some helper functions and some basic parameters. It specifies some bash history parameters and, for security purposes, disables keeping a permanent history file for the root user. It also sets a default user prompt. It then calls small, single purpose scripts in the /etc/profile.d directory to provide most of the initialization.

For more information on the escape sequences you can use for your prompt (i.e., the PS1 environment variable) see info bash -- Node: Printing a Prompt.

cat > /etc/profile << "EOF"
# Begin /etc/profile
# Written for Beyond Linux From Scratch
# by James Robertson <jameswrobertson@earthlink.net>
# modifications by Dagmar d'Surreal <rivyqntzne@pbzpnfg.arg>

# System wide environment variables and startup programs.

# System wide aliases and functions should go in /etc/bashrc.  Personal
# environment variables and startup programs should go into
# ~/.bash_profile.  Personal aliases and functions should go into
# ~/.bashrc.

# Functions to help us manage paths.  Second argument is the name of the
# path variable to be modified (default: PATH)
pathremove () {
        local IFS=':'
        local NEWPATH
        local DIR
        local PATHVARIABLE=${2:-PATH}
        for DIR in ${!PATHVARIABLE} ; do
                if [ "$DIR" != "$1" ] ; then
                  NEWPATH=${NEWPATH:+$NEWPATH:}$DIR
                fi
        done
        export $PATHVARIABLE="$NEWPATH"
}

pathprepend () {
        pathremove $1 $2
        local PATHVARIABLE=${2:-PATH}
        export $PATHVARIABLE="$1${!PATHVARIABLE:+:${!PATHVARIABLE}}"
}

pathappend () {
        pathremove $1 $2
        local PATHVARIABLE=${2:-PATH}
        export $PATHVARIABLE="${!PATHVARIABLE:+${!PATHVARIABLE}:}$1"
}


# Set the initial path
export PATH=/bin:/usr/bin

if [ $EUID -eq 0 ] ; then
        pathappend /sbin:/usr/sbin
        unset HISTFILE
fi

# Setup some environment variables.
export HISTSIZE=1000
export HISTIGNORE="&:[bf]g:exit"

# Setup a red prompt for root and a green one for users.
NORMAL="\[\e[0m\]"
RED="\[\e[1;31m\]"
GREEN="\[\e[1;32m\]"
if [[ $EUID == 0 ]] ; then
  PS1="$RED\u [ $NORMAL\w$RED ]# $NORMAL"
else
  PS1="$GREEN\u [ $NORMAL\w$GREEN ]\$ $NORMAL"
fi

for script in /etc/profile.d/*.sh ; do
        if [ -r $script ] ; then
                . $script
        fi
done

# Now to clean up
unset pathremove pathprepend pathappend

# End /etc/profile
EOF