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).