Date: Mon, 27 Jan 1997 09:22:19 -0500 (EST) From: John Fieber <jfieber@indiana.edu> To: bope onrt <spy211@hotmail.com> Cc: www@FreeBSD.ORG Subject: Re: question Message-ID: <Pine.BSI.3.95.970127090625.8252A-100000@fallout.campusview.indiana.edu> In-Reply-To: <19970127055354.27880.qmail@hotmail.com>
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On 27 Jan 1997, bope onrt wrote: > hi,i just have one question,,what is a unix shell?I would just like > to no what the meaning of "SHELL" means..if you could get back to > me i would be thankful.. When you log in from a character based terminal, the "shell" is the user interface. When you type in a command, it is the shell that reads it and arranges for the command(s) to be executed. For example: % ls | wc -l the `%' is the shell's prompt. `ls' and `wc' standard unix program (list files, word count). The `|' is interpreted by the shell as meaning ``take the output of the first program and feed it to the input of the second''. The shell has to locate where the `ls' and `wc' programs are on the system (using the PATH environment variable), arrange for them to be run such that the output of one goes to the other. If you are familiar with MS-DOS, the shell serves the same role as COMMAND.COM, only is quite a bit more powerful. Jast as you can create `batch' files in MS-DOS that are executed by COMMAND.COM, it is not uncommon to find quite complex programs written for the Unix shell. You should also be aware that there are two commonly used Unix shells: the bourne shell (sh) and the `C' shell (csh). Actually, there are several variants of each one available. The choice of which one to use is somewhat of a religious issue. -john
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