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Each | tells the shell to connect the standard output of the command on the left to the standard input of the command on the right by an inter-process communication mechanism called an (anonymous) pipe, implemented in the operating system. Pipes are unidirectional; data flows through the pipeline from left to right.
The UK/Ireland keyboard has both symbols engraved: the broken bar is given as an alternate graphic on the "grave" key; the solid bar is on the backslash key. The broken bar character can be typed (depending on the layout) as AltGr+` or AltGr+6 or AltGr+⇧ Shift+\ on Windows and Compose!^ on Linux.
Every pipe is placed in the root directory of the named pipe filesystem (NPFS), mounted under the special path \\.\pipe\ (that is, a pipe named "foo" would have a full path name of \\.\pipe\foo). Anonymous pipes used in pipelining are actually named pipes with a random name. They are very rarely seen by users, but there are notable exceptions.
A good example for command piping is combining echo with another command to achieve something interactive in a non-interactive shell, e.g. echo-e 'user\npass' | ftp localhost. This runs the ftp client with input user, press return, then pass. In casual use, the initial step of a pipeline is often cat or echo, reading from a
A metacharacter is a character that has a special meaning to a computer program, such as a shell interpreter or a regular expression (regex) engine.. In POSIX extended regular expressions, there are 14 metacharacters that must be escaped — preceded by a backslash (\) — in order to drop their special meaning and be treated literally inside an expression: opening and closing square brackets ...
Some recent embedded systems also use proprietary character sets, usually extensions to ISO 8859 character sets, which include box-drawing characters or other special symbols. Other types of box-drawing characters are block elements , shade characters, and terminal graphic characters; these can be used for filling regions of the screen and ...
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This pipe will be accessible with something like /dev/fd/63; you can see it with a command like echo <(true). Execute the substituted command in the background (sort file2 in this case), piping its output to the anonymous pipe. Execute the primary command, replacing the substituted command with the path of the anonymous pipe.