## General

Since many basic tasks can be done graphically, the command line interface became less important. There are still some occasions, where it is very useful:

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A sequence of system commands can be written into a file (called ``shell script'' or ``batch file'') and called like a program. Typical command languages contain special programming constructs like tests and loops. This allows to automate rather complex tasks.

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In case of system problems (e.g. hardware defects, incorrect startup scripts) system commands are helpful to isolate or fix the problem.

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Especially on UNIX systems exist a set of small, but useful utilities, which can be combined to solve common problems in one line.

In DOS a batch file has the extension .bat and is called without the extension, e.g. file initall.bat is executed with initall.

In UNIX a script can be named arbitrarily and the full name has to be used, e.g. file initall.pl has to be called as initall.pl.

The basic form of a system command is

COMMAND OPTIONS ARGUMENTS,

with:

 COMMAND name of the command OPTIONS special flags or switches which modify the command ARGUMENTS objects, the command operates on

In the line

dir /o /p c:\windows

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dir is the command, meaning ``list all files in the given directory'',
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c:\windows is the directory to list
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/o /p are options meaning ``display in alphabetic order'' (/o) and ``show one screen at a time'' (/p).

Peter Junglas 8.3.2000