This document gives an overview of shell startup files. This document is applicable to AIX Versions 3 and 4.
At login, the shell defines the user environment after reading the shell startup files. The characteristics of the user environment are defined by the values given to the environment variables. This environment is maintained until the user logs off the system.
Login Execution Sequences:
The /etc/environment and /etc/security/environ files are executed regardless of what shell is run.
Even shells started by rexedc and rshd should set all the environment
varibles that are defined in the /etc/environment file. See the following:
AIX 3.2 APARs IX59863 and IX56867
AIX 4.1 APAR IX60035
The /etc/environment file sets up the user environment such as the minimal search path, time zone, language etc. This file is not a shell script and does not accept data in a format other than the
Name=<Value>
format. This file is executed by all processes started by the init process and it affects all login shells.
The /etc/security/environ file is an ASCII file that contains stanzas with the environment attributes for individual users. Each stanza is identified by a user name and contains attributes in the
Attribute=<Value>
format. Each user stanza can have the following attributes:
Korn shell C Shell Bourne Shell
/etc/environment /etc/environment /etc/environment
/etc/security/environ /etc/security/environ /etc/security/environ
/etc/profile /etc/csh.cshrc /etc/profile
/etc/csh.login
$HOME/.profile $HOME/.cshrc $HOME/.profile
$HOME/.kshrc $HOME/.login
NOTE: $HOME/.login and /etc/csh.login (csh) and $HOME/.profile and /etc/profile (ksh and bsh) get executed only at login. /etc/.cshrc and $HOME/.cshrc (csh) and $HOME/.kshrc (ksh) get executed every time a subshell is invoked. They are generally used to define aliases and shell variables (for example, noclobber, ignoreeof). It is recommended that you only use shell built-in commands in these files because using other commands could increase the startup time for shell scripts.
Shell startup files define search paths, set informative shell prompts, set history files (csh and ksh only), and set terminal types.
#!/bin/csh
######################
#SAMPLE .login file #
######################
#define search path
set path=(/bin /usr/bin $HOME/bin /etc .)
#set prompt to reflect the current working directory
alias cd 'chdir \!* > /dev/null; set prompt="$cwd %"'
#set up history file
set history=20
#set up terminal type
eval `tset -s -Q -m ':?ibm3151'`
#-s flag prompts the C shell setenv process.
#The above line prompts users to set
#the TERM environment variable,
#hitting enter will set TERM to ibm3151
#!/bin/ksh
#######################
#SAMPLE .profile file #
#######################
#define search path
PATH=/bin:/usr/bin:$HOME/bin:/etc:.
#set prompt to refect the current working directory
PS1='$PWD $'
# To include variables LOGNAME and HOSTNAME to the PS1
# variable - set PS1 as follows
# PS1='${LOGNAME} @${HOSTNAME} ${PWD} $'
#set up history file
HISTFILE=$HOME/.my_history #default is $HOME/.sh_history
HISTSIZE=20
#set up terminal type
TERM=`termdef`
export PATH, PS1, TERM
NOTE: Setting the bsh prompt to include the current working directory is slightly more complicated because Bourne shell does not have the PWD variable, but you can use the pwd command to build your own function. For example, put the following in the .profile:
xcd () { cd $*; PS1="`pwd` $"; }
and use xcd instead of cd to move around.
Feature bsh csh ksh
compatible with bsh n/a no yes
job control yes yes yes
command history no yes yes
command line editing no yes yes
aliases no yes yes
noclobber
(protecting files been
overwritten) no yes yes
ignoreeof
(ignore control-D) no yes yes
logout file no yes no
Rsh is identical to bsh, except that the following are NOT allowed:
tsh differs from Korn shell in the following ways:
However, if a user working in a restricted Korn shell invokes a Korn shell script, then the script will run normally. That is, a restricted Korn shell does not restrict Korn shell scripts.
There are two ways to create a restricted Korn shell. One way is to invoke the program named rksh. Another way is by setting the SHELL variable. This variable holds a pathname. If the first letter of the leafname of this pathname contains the letter r, then the system invokes a restricted Korn Shell. Otherwise, the system invokes a regular Korn shell. For those unfamiliar with this term, the leafname of a pathname is the last (rightmost) component of the pathname.
For example, the following assignment in a startup script will cause the system to invoke a restricted Korn shell:
SHELL=/usr/bin/rksh
However, the following assignment in a startup script will cause the system to invoke a regular Korn shell:
SHELL=/usr/bin/ksh