bash vs csh(==tcsh) programming:

The make*.doc files have a mixture of csh and bash scripting instructions.
The typical process to use these scripts is to cut them from
the make*.doc file and paste them onto your shell prompt.

This document describes how to work with either kind of script
from either kind of shell.

See also: on-line tcsh help:
    http://www.techfak.uni-bielefeld.de/rechner/shells/tcsh/top.html
on-line bash tutorial: http://www.hypexr.org/bash_tutorial.shtml
    http://www.faqs.org/docs/bashman/bashref.html#SEC_Top
or: 'man bash' for bash man page, 'man tcsh' for tcsh man page

The procedure to allow this to work is to create in your
HOME directory the appropriate ~/.*shrc file for both shells
so that your working environment will be the same in
either shell environment.

With both sets of definitions in place, using either kind of
script can be done by entering the "other" shell when you
encounter the "other" shell script instructions, then exit
back to your default shell.  To enter the "other" shell at
your default shell prompt, enter one of the two commands, bash or tcsh:
#	from bash to csh:
[hiram@kk9 /tmp] tcsh
<hiram@kk9 /tmp>
#	from csh to bash:
<hiram@kk9 /tmp> bash
[hiram@kk9 /tmp] 

It is a good idea to have a different prompt setting to help
recognize your shell.  When in doubt, do a 'ps -f' and you
will see the nest of shells as child processes of each other.
bash uses the environment variables PS1 and PS2, csh uses
the shell variable: prompt.

Your default login shell probably already has one of these files:
	~/.bashrc - for bash login shells
	~/.cshrc or .tcshrc - for csh or tcsh login shells

The complication is that they do not use the same kind
of syntax for definitions.  You can not simply copy from
one to the other.  The differences are simple.

====================================================================
SYNTAX differences
====================================================================
1.  Setting environment variables in the ~/.*shrc files:
#	bash syntax:
export CVSROOT=/projects/compbio/cvsroot
#	csh syntax:
setenv CVSROOT /projects/compbio/cvsroot
#	setting csh shell variables:
set prompt = '<%n@%m %c> '
#	the bash prompt is an environment variable:
export PS1='[$LOGNAME@$HOST ${PWD##}] '

    *NOTE*: do *not* use white space around the = sign in the bash assignment.
    If you do not "export" a bash variable, it will not be inherited by
    sub-shells.
    See also, programming the bash prompt:
	http://en.tldp.org/HOWTO/Bash-Prompt-HOWTO/

2.  alias statements are the same in bash and csh
alias ma='make HG_WARN=-Wall'

3.  if statement syntax is different:
#	bash syntax:
if [ -s /usr/lib/mysql/libmysqlclient.a ]; then
    export MYSQLINC=/usr/include/mysql
    export MYSQLLIBS="/usr/lib/mysql/libmysqlclient.a -lz"
fi
#	csh syntax:
if( -s /usr/lib/mysql/libmysqlclient.a ) then
    setenv MYSQLINC /usr/include/mysql/
    setenv MYSQLLIBS "/usr/lib/mysql/libmysqlclient.a -lz"
endif

    *NOTE*: You *must* use white space around the [ and before the ]
	since those symbols are shell built-in commands to bash !
    See also: 'man test' for a list of the file compare operators

====================================================================
NOTES:
====================================================================
Actual script files can be run from either shell without difficulty.
    A bash shell script file begins with a first line:
#!/bin/sh
    A csh shell script file begins with a first line:
#!/bin/csh -fe

    These initial lines are interpreted to specify which shell to
    use for the script.  So, if the script is in a shell, you need
    do nothing special to operate it.  Just run it as a command from
    your shell prompt.

Substitutions:

There are too may ways to do this in either shell to do this
subject justice.  A few pointers:

bash and csh have completely different substitution methods to edit
strings in variables.  For example, csh typically uses the : operator
to parse strings:
<hiram@hgwdev test> pwd
/tmp/test
<hiram@hgwdev test> echo $PWD
/tmp/test
<hiram@hgwdev test> echo $PWD:t
test
<hiram@hgwdev test> echo $PWD:h
/tmp

The same head and tail functions in bash are done by the dirname and
basename commands:
[hiram@hgwdev /tmp/test] echo $PWD
/tmp/test
[hiram@hgwdev /tmp/test] echo `basename $PWD`
test
[hiram@hgwdev /tmp/test] echo `dirname $PWD`
/tmp

Modifying strings in csh:
<hiram@hgwdev test> echo $PWD:s/test/testing/
/tmp/testing

Modifying strings in bash:
[hiram@hgwdev /tmp/test] echo ${PWD/test/testing/}
/tmp/testing/


====================================================================
This file last updated: $Date: 2006/07/25 20:12:51 $