2.8 Identifying Login Shells

When you first log in to a UNIX system from a terminal, the system usually starts a login shell. This is where you want to do general setup - initialize your terminal, set environment variables, and so on. Here the C shell reads your .login file, and Bourne-type shells read .profile (bash can read others).

Other shells are either subshells (38.4) (started from the login shell) or separate shells started by at (40.3), rsh (1.33), etc. These shells don't read .login or .profile.

To make it possible to find out which you've got, add the line below to the top of your .login or .profile file: The line sets a shell variable (6.8) named loginshell:

set loginshell=yes   ...csh

loginshell=yes   ...sh-type shells

Now wherever you need to know the type of shell, use tests like:

if $? if [...]	if ($?loginshell) ...csh if [ -n "$loginshell" ] ...sh-type shells

This works because only login shells read .login or .profile. The loginshell variable will be defined only in login shells.

Article 7.9 shows another solution.