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bash scripting

From: cbbrowne@knuth.brownes.org (Christopher Browne)
Newsgroups: comp.os.linux.misc
Subject: Re: Batch for Linux
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Date: Sat, 16 Sep 2000 13:59:41 GMT

Centuries ago, Nostradamus foresaw a time when Stuart Mika Hankel would say:
>Hello. How can i make a batch for Linux?
>I've heard that i can make a 'script'. It's the same like BAT files for DOS?
>How can i generate it? What's the extension?
>I need to program two command line orders.

BAT files are reminiscent of script files, albeit where the canonical
scripting languages are actually somewhat powerful languages...

There is no such thing as an "extension" on Unix/Linux; that is an
artifact of the MS-DOS FAT filesystem.

On Linux, while it is _conventional_ for C source code to end with the
".c" suffix, and object code to end with ".o", and the likes; those are
NOT "extensions,"

Executable files are not expected to have any sort of "extension" or
"suffix;" the fact that they are executable is indicated by the
file permissions (see "man chmod"), and the start of the file will
indicate an "execution signature," whether by containing a binary
prefix that is recognized by the kernel, or by starting with the
characters #!, which is the convention to indicate that the file 
contains some form of "script."

The scripting language that is _guaranteed_ to be available on 
virtually _any_ Linux (save for fairly obscure distributions) is
GNU Bash; you might try "man bash" to get information on that
language.

Korn shell (ksh) is ubiquitous on commercial Unixes, and is available
on virtually all Linux distributions; csh/tcsh are the other "real
popular" option, albeit deprecated for scripting.  Perhaps the
most powerful of the bunch is zsh, which is the "most-hacked-on shell
language."

The convention for making a Bash script would be to find where Bash
is via "which bash" and then writing a script such as:

#!/bin/bash
# Simple bash script that lists all the full filesystems
export OURHOME=/tmp
cd $OURHOME
df > spaceinfo.$$
grep "100\%" spaceinfo.$$ > full.$$
cat full.$$
rm spaceinfo.$$ full.$$

Save as "myscript"

Then
% chmod a+x myscript
% ./myscript
%

On my system, there weren't any full filesystems, so this showed
nothing.
-- 
cbbrowne@ntlug.org - <http://www.ntlug.org/~cbbrowne/scripting.html>
All extremists should be taken out and shot.

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