Linux Bash commands
In this chapter we work with Linux interface
in text mode using Linux bash script, in other words, from the console or terminal (Linux shells).
The novice user may think that he will never
work in this mode, because there is a graphical mode.
However, this opinion is erroneous, because many of the turns faster and
more convenient to carry it in text mode. Even in
graphical mode, you'll often open a window emulator
terminal, and perform the necessary actions in that window. After
text-mode operating system Linux - this is not what the text
odnozadachnoy mode MS-DOS. Since Linux - this
multitasking OS, which is already in text mode is provided an opportunity
work in multiple windows (about switching terminals and we told the
previous article). And for editing simple text or
html-file is not necessarily enough to run heavy and
slow (especially on "soft" computers) graphics
shell.
What shell?
As mentioned above, although we often say,
that the user works with the operating system,
in fact it is not true, because in the interaction with
user arranges a special program. There are two types
such programs - the shell or shell, to work in text mode (command line interface) and
graphical user interface GUI (Graphical User
Interface ), organizing the interaction with the user in
graphical mode.
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Immediately I must say that, in principle, any program
in Linux can be run as a shell (if you are running
X-server, see Chap. 6 ), and a graphical interface
user. Running programs from the shell is equivalent (double)
clicking on the program icon in the GUI. Arguments
program in text mode is similar to what we "throw"
something on the program icon in the graphic. But, on the other hand,
Some programs are not designed to run through the GUI and
respectively, can be executed only from the command line.
Actually, the name "shell" not withstand scrutiny. In my opinion it would be better to call this
program command processor, as it is called command.com in MS DOS,
or command interpreter. But so it became the custom for all UNIX-based systems
that the command interpreter for text mode is called shell.
Once (in the first UNIX-based systems), it was
program called sh ,
which was reduced from sh ell . Then there were
developed several of its improved variants, in particular, Bourne
shell - an enhanced version sh ,
written by Steve Bourne (Steve Bourne). The project GNU (project
R. Stallman for the development of free software, see www.gnu.org )
created shell bash ,
whose name stands B ourne- a gain
Sh ell , ie, "Bourne again shell.
In English in this title is viewed more and play on words,
due to the fact that Bourne sounds like borne (born, born)
get "born again shell". Envelope bash
was written by Brian Fox (Brian Fox - basic
developer) and Chet Ramey (Chet Ramey). It bash
we will continue to review, and everywhere below, which refers to
shell at all, you can safely assume that this is a bash .
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Itself envelope bash
does not perform any applications. But it provides
execution of all applications: the calling program, they start
and the organization of input / output. In addition, Shell is responsible for working with
environment variables and perform some transformations
(Substitution) arguments. But the main feature of the shell, which
makes it a powerful tool for the user - is that
It includes a simple programming language. How long have proved
In mathematics, any algorithm can be constructed from a pair of triple-core
operations and a conditional operator. The implementation of conditional statements
(As well as operators of the cycle) and assumes the shell. It uses
all other utilities and programs (and those that are composed
operating system, and those that are installed separately) as the basic
operations supported by its programming language, provides
transfer of arguments, as well as the transfer of the results of their work to other
program or user. The result is a very powerful
programming language. And this is the main force and one of the essential
shell functions.
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