Shell - Startup Files

1 tcsh

• tcsh executes system-wide startup file usually located at /etc/csh.cshrc
• This fi le is not usually editable for everyone.
• tcsh will then executes .tcshrc and if not found executes .cshrc in local home directory.
• If tcsh is executed as login shell, then global con g is executed from /etc/csh.login followed by ~/.login fi le.

2 csh

• csh behaves much the same as tcsh. It executes system-wide startup file usually located at /etc/csh.cshrc, which is editable by priviledged users.
• For login shell, /etc/csh.login fi le is executed in addition to /etc/csh.cshrc {Need to double check if both or only one of .login .cshrc is executed when login shell is invoked.}
• tcsh will then execute ~/.tcshrc and if not found execute ~/.cshrc file.
• If tcsh is executed as login shell, then global con g is executed from /etc/csh.login followed by .login file in personal home directory.

3 bash

3.1 For login shell or with --login option

• Bash looks for system wide settings in /etc/profile le which is not editable to non-root user.
• After reading that le, it looks for ~/.bash_profile, ~/.bash_login and ~/.profile in that order. It executes the fi rst fi le that is found and readable. It does NOT execute all the files.
• Using --noprofile option will inhibit the above lookup.
• When shell is exited, bash executes commands from ~/.bash_logout file.

3.2 Started as interactive non-login shell

• Bash reads and executes commands from ~/.bashrc. This can be overridden by using --norc option.
• The --rcfile will override above behavior and bash will read and execute commands from ~/.bashrc instead.
• There are many other ways to invoke a shell and they can be read in [2]

References
[1] http://www.acm.uiuc.edu/workshops/cool unix/tcsh-startup.html
[2] http://www.gnu.org/software/bash/manual/html node/Bash-Startup-Files.html